home

discover for more **[|America's Coolest Marketer]** resources With the emergence of three-dimensional computer graphics, the ability to simulate real environments has become a major tool in the representation and interaction of spatial data, which can be observed, manipulated, and applied to a wide range of GIS based problems. The goal of Virtual Reality in GIS is to step beyond the comfortable reach of two dimensional (2D) representations to higher dimensions of visualization. To model reality most clearly, it certainly makes sense that we strive to map what we actually experience (1).

__Definitions__
GIS is a system of hardware and software used for storage, retrieval, mapping, and analysis of geographic data. Practitioners also regard the total GIS as including the operating personnel and the data that go into the system. Spatial features are stored in a coordinate system (latitude/longitude, state plane, UTM, etc.), which references a particular place on the earth. Descriptive attributes in tabular form are associated with spatial features. Spatial data and associated attributes in the same coordinate system can then be layered together for mapping and analysis. GIS can be used for scientific investigations, resource management, and development planning. (1)
 * __** GIS **__
 * ===__**Virtual Reality**__===

=
An artificial environment that is created with software and presented to the user in such a way that the user suspends belief and accepts it as a real environment. On a computer, virtual reality is primarily experienced through two of the five senses: sight and sound. (2)======

The following are alternative f virtual reality which incorporate the type of advanced technology that may be used to create a virtual environment: // **Virtual Reality** is electronic simulations of environments experienced via head mounted eye goggles and wired clothing enabling the end user to interact in realistic three-dimensional situations. // (3)

// **Virtual Reality** is an alternate world filled with computer-generated images that respond to human movements. These simulated // // environments are usuall //// y visited with the aid of an expe //// nsive data sui //// t whi //// ch //// features stereophonic video goggles and fiber-optic data gloves. // (4) Programming Language for creating and displaying (rendering) three-dimensional (3-D) objects and spaces on the web. Environments can contain animation, audio and video files, and hyperlinks to simulate realistic views of the inside and outside of buildings, bridges, tunnels, etc. These views change in real time in response to the computer users movements or mouse clicks. (6) Rendering for interactive media, such as games and simulations, is calculated and displayed in real time, at rates of approximately 20 to 120 frames per second. In real-time rendering, the goal is to show as much information as possible as the eye can process in a fraction of a second (a.k.a. in one frame. In the case of 30 frame-per-second animation a frame encompasses one 30th of a second). The primary goal is to achieve an as high as possible degree of photorealism at an acceptable minimum rendering speed (usually 24 frames per second, as that is the minimum the human eye needs to see to successfully create the illusion of movement) (7)
 * // The terms //** **virtual worlds**//,// virtual cockpits//, and// virtual workstations //were used to// // describe specific projects…. In 1989, Jaron Lanier,, coined the term // virtual reality //to bring all of the virtual projects under a single rubric. The term// // therefore typically refers to three-dimensional realities implemented with stereo. (5) //
 * ===__Virtual Reality Modeling Language (VRML)__===
 * ===__Real-time__===

Real time systems are defined as those systems in which the correctness of the system depends not only on the logical result of computation, but also on the time at which the results are produced (8). > Computer aided design - provides the user with input-tools for the purpose of streamlining design processes; drafting, documentation, and manufacturing processes. (10)
 * ===__CAD__===

To make visible; to draw. The term comes from the graphics world where a rendering is an artist's drawing of what a new structure would look like. In computer-aided design (CAD), a rendering is a particular view of a 3D model that has been converted into a realistic image. It includes basic lighting techniques as well as more sophisticated effects that simulate shadows, reflection and refraction.(12)
 * ===__Rendering__===

Within a computer system, it means to convert any coded content to the required format for display or printing. Although the term is typically used to refer to images, it may refer to any data.For example, an HTML page, which contains text and graphics, is said to be "rendered" when it is displayed.(12)

A LiDAR (Light Detection And Ranging) system rapidly transmits laser pulses that reflect off the terrain and other landscape features such as infrastructure and vegetation. The return pulse is converted to electrical impulses and collected by a high-speed data recorder. Because the speed of light is known and the time interval of the pulse from transmission to return has been measured, the range or distance can be derived. (13) Photogrammetry is the science of making reliable measurements of physical objects and the environment, by measuring and plotting data from aerial photographs and remote-sensing systems against land features identified in ground control surveys. Generally, this is performed in order to produce planimetric, topographic, and contour maps. (13)
 * ===__LiDAR__===
 * ===__Photogammetry__===

(also called stereoscopic or 3-D imaging) refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Both of these 2-D offset images are then combined in the brain to give the perception of 3-D depth. (14)
 * ===__Stereoscopy__===

A LiDAR survey produces a large mass of points known as a Point Cloud. A Classified Point Cloud is simply the point cloud classified into feature types. At a minimum, the point cloud is classified into ground and non-ground. The data can then be further classified into features such as powerlines, buildings and vegetation. (13)
 * __ **- Point Cloud** __

Two dimensional plots are useful for visualizing the relationship between two numerical variables, such as the line graph and the scatter plot. They can also be used to present multivariate view of several data sets, such as the parallel coordinate plot (text).
 * **__ Two-Dimensional Plots __**

These plots (sometimes referred to as surface plots) are used to visualize the relationships among three numerical variables (see in the adjacent figure the percentage reflectance of the land cover in a Landsat MSS (Multispectral Scanning System) scene at leach pixel for a part of Huntsville, Alabama). The technique used in conventional cartographic visualization. Spatial variation and patterns resulting from data analysis can be effectively depicted using different colours and symbology.
 * **__ Three-Dimensional Plots __**
 * **__ Two-Dimensional Planimetric Views __**

A three-dimensional perspective view can be created in a number of ways:
 * **__ Three-Dimensional Perspective Views __**


 * Geometric modeling:** generates views ranging from simple three-dimensional perspective drawings of the landscape to relatively complex wireframe models capable of showing local details at large scales.


 * Video Imaging:** produces photorealistic quality views that can faithfully depict the conditions of the landscape


 * Geometric Video Imaging:** is a hybrid approach combining geometric techniques (so that it can take advantage of the relative merits if the parent techniques, i.e., ability to depict small changes and high image).


 * Image Draping:** a well-established function of GIS and image-processing software that involves the draping of an image, such as digital orthophoto of a classified satellite image, onto a three-dimensional perspective view created by geometric modeling. The figure below shows image draping techniques based from initial two-dimensional planimetric views to produce a DEM.



Animation is the computer graphics technique for visualizing time-dependent spatial data in sequence. two-dimensional planimetric views have been most commonly used for animation. However, two dimensional and three-dimensional plots can also be usefully employed to visualize temporal changes of spatial data. When an animation sequence is produced in three dimensions, it is called a **fly-through**, in it's most sophisticated form, an animation sequence can be visualized in VR (also called virtual world or virtual environment). In VR, the user can freely move to and view any part of the animated scene. It is also possible to hyperlink individual objects in VR to related sources of geospatial and nongeospatial information of the same server across the internet.
 * __** Animation **__

media type="youtube" key="Ek3_K3eisJY?version=3" height="360" width="640" align="center"

__Chronology__
The most important component contributing to the production of a high quality Virt ual Reality is the ability to render a three-dimensional environment. Advancement in the field of 3d graphic representation within GIS is directly related to the evolution of 3D graphic production technologies and level computer processing power available. As technology advances in general, we see parallel advancement in the field of computer generated graphics and integration of GIS. Prior to the computerized map, most spatial analyses were severely limited by their manual processing procedures. The computer has provided the means for both efficient handling of voluminous data and effective spatial analysis capabilities. From this perspective, all geographic information systems are rooted in the digital nature of the computerized map. (16)

3D technology can be traced all the way back to the beginning of photography, when In 1844 David Brewster invented the Stereoscope. This was one of the first steps taken toward production of a three dimensional environment. The stereoscope was particularly useful in interpreting elevation changes over a given area. Development toward GIS lay dormant until the advent of computer technology. (14)
 * 1844**


 * 1970's**
 * -**The pioneering work during this period established many of the underlying concepts and procedures of modern GIS technology.

-The very first output from a GIS came from a line printed attached to a large mainframe computer. Using individual letters (e.g., “W” for water) or over-striking letters, line printed grayscale maps began to show the patters and results of the first GIS analyses. In these pioneering years, 3D presentations were not viable due to the limitations of computer performance.


 * -** The first microprocessor, RAM chip, removable disk (floppy drive), network, word processors, and personal computers - all of which were required for the future development of three dimensional GIS. (16)

-radical change in the format of mapped data— from analog inked lines on paper, to digital values stored on disk

-The development of the first computer maps. The points, lines and areas defining geographic features on a map are represented as an organized set of X, Y coordinates. Various colors, scales, and projections can be chosen and exchanged in order to accurately represent different types of land cover. (17)

-In 1979 George Lucas hired a team of computer scientists, led by Dr. Edwin Catmull, to create a digital model of an X-Wing fighter from Star Wars. This had huge implications in the entertainment industry and provided funding which furthered the development of three dimensional image processing. (18)

-The advent of Spatial Database Management - linking computer mapping capabilities with traditional database management capabilities. In these systems, identification numbers are assigned to each geographic feature. With spatial database management the user is able to point to any location on a map and instantly retrieve information about that location.
 * 1980's**

-Two alternative data structures for encoding maps emerged: 1. Vector Models - losely mimics the manual drafting process by representing map features (discrete spatial objects) as a set of lines which, in turn, are stores as a series of X,Y coordinate

2. Raster Models - establishes an imaginary grid over a project area, and then stores resource information for each cell in the grid (continuous map surface)

These two models were viewed in a competitive manner, and no model encompassing both was produced. (17)

-In 1980 Dana Tomlin has developed the Map Analysis Package (MAP). MAP is a raster-based GIS that was eventually installed at several thousand locations around the world. (19)

-in 1981 ESRI launched ARC/INFO - a full-featured geographic information system produced by ESRI, and is the highest level of licensing (and therefore functionality) in the ArcGIS Desktop product line. It was originally a command-line based system. The command-line processing abilities are now available through the GUI of the ArcGIS Desktop product. (20)

-Hardware vendors continued to improve digitizing equipment, with manual digitizing tablets giving way to automated scanners at many GIS facilities. A new industry for map encoding and database design emerged, as well as a marketplace for the sales of digital map products. Regional, national and international organizations began addressing the necessary standards for digital maps to insure compatibility among systems. (17)

**1990's** We witnessed the explosive growth of the Internet, the thrust toward computerization of buisiness and government services, and the deployment of data warehouses and national data infrastructures. These have created a widespread need for visualization techniques by the broader buisiness and technical communities to gain insight into their huge and complex holdings. A new branch of visualization, called information visualization (InfoVis), emerge to address some of the fundamental problems associated with the new classes of data and their related analysis tasks.vHypertext Markup Language (HTML) is the predominant markup language for web pages. Virtual Reality Modeling Language (VRML) is also introduced. (C) (D)

__1991__ IdSoftware releases the first ever first-person shooter computer game. The game is not truly 3D as visualization of ramps and slants are absent - visually Wolfenstein3D is based on affine texture mapping to give illusion of true 3D. This sparks interest in the entertainment industry, and results in increased development toward true 3-dimensional graphics.The secret behind engine's performance is vertical scanline scaling algorithm. Unlike later engines and hardware rasterizers, the texture coordinate for the pixel is not calculated at runtime. Instead, a fixed set of several hundreds rendering functions is generated during game startup (or viewport size change) where all memory offsets are fixed. To keep the number of these procedures small, height is quantized, which can be easily seen when player is close to the wall, but not looking at it at a right angle.(K)(L)

__1993__ Cambray purposes CAD models for 3-dimensional objects combined with Digital Terrain Models as a way to create 3D GIS that is a combination of Constructive Solid Geometry (CGS) and Boundary Representation (X).

__1995__ Pigot developed a 3-dimensional topological model based on 0, 1 2 3 cell, which maintains an explicit descripton of relationships between cells (X).

__1996__ 1.Pilouk focused on the use of Triangulated Irregular Network (TIN) datastructure and relational database for 2D and 2.5D spatial data. He purposed an integrated data model for 3D GIS which produced a practical approach to the problem. Moreover, the author develops the Tetrahedron Network (TEN) data structure that is based on simplexes. The structure assures strict consistency check (X). 2. IdSoftware releases Quake: Based on an all-new graphics engine, it was the first truly 3D video game, allowing players to interact with the virtual worlds created by id like never before. The Quake game engine is adapted and used by landscape planning researchers.

__1997__ 1.NASA launches Landsat 7 carrying Enhanced Thematic Mapper Plus (ETM+). This allows for a massive amount of data collection for use in the GIS community(17). 2. Introduction of Virtual Reality Modeling Language (VRML) to model geospatial data, and Java to develop an interface to interact with the VRML. Researchers are now able to concentrate on data structuring/analysis and leave the rendering issues to browsers offered freely on the internet(FF).

__1998__

TerraServer started as a joint research project between Aerial Images, Inc., Microsoft, the USGS, and Compaq. . Aerial Images, Inc. wanted to sell imagery online and Microsoft Research needed a large database to demonstrate the capabilities of its new database software. Under the agreement Microsoft built the TerraServer application and agreed to host the SPIN-2 data and run the site for eighteen months following the formal site initiation. This was one of the first leaps toward the use of the internet and GIS (17).

__1999__ 1.NASA’s Terra EOS launched - a multi-national NASA scientific research satellite in a sun-synchronous orbit around the Earth (GG). 2.IKONOS launched -a commercial earth observation satellite, and was the first to collect publicly available high-resolution imagery at 1- and 4-meter resolution. It offers multispectral (MS) and panchromatic (PAN) imagery (GG). 3.

Contemporary maps take on radical new forms of display beyond the historical 2D planimetric paper map. User expectations demand spatial information on a 3D view of the terrain. Virtual reality transforms the information from pastel polygons to rendered objects of trees, lakes and buildings for near photographic realism. Embedded hyperlinks access actual photos, video, audio, text and data associated with map locations. Immersive imaging enables the user to interactively pan and zoom in all directions within a display (17)
 * 2000's**

__2000__ 1.De la Losaand Cervelle (1999) and Pfund (2001) propose object-oriented models similar to Molenaar’s onebut they have included several more explicitly stored spatial relationships. For example, De laLosa maintains the relationship arc-faces and introduces a strict ordering of faces (R). 2. Abdul-Rahman manipulated 3D objects via 3D raster-based objects approach and had generated information via proprietary object-oriented DBMS. The results showed the 3DFDS is capable of 3D spatial objects as the objects were created via 3D triangular irregular network approach. Abdul-Rahman focuses on the object oriented TIN (2D and 3D) based GIS. The conceptual and logical model are based on the Molenaar’s data model (R).

__2002__ 1.Envisat launched ** - ** An Earth observation satellite. Its objective is to service the continuity of European Remote-Sensing Satellite missions, providing additional observational parameters to improve environmental studies (GG). 2. Introduction of a flexible VRML-based terrain model. It can simplify the changes of display range and attach an automatic changeover by placing the given terrain models in 3D space. (R)

__2003__ 1.ISRO's RESOUCESAT-1 (IRS P6) launched - intended to not only continue the remote sensing data services provided by IRS-1C and IRS-1D, but also vastly enhance the data quality (GG). 2. Zhang Jing et al discussed the 3D GIS modeling technology in urban GIS by combining the traditional GIS and virtual reality (R). 3.Elizabeth Burson also presents two methods of 3D GIS modeling for professionals to incorporate models such as buildings, caves, viewsheds and many man-made objects into their greater GIS environment (R). 4.H Kolbe et al. proposed a unified model to represent spatial objects by geometric, topological, and thematic properties (R).



__2004__ 1.NASA launches Worldwind - a free open source virtual globe developed by NASA and open source community for use on personal computers running Microsoft Windows. The program overlays NASA and USGS satellite imagery, aerial photography, topographic maps and publicly available GIS data on 3D models of the Earth and other planets (JJ).

__ 2005 __ ISRO's CARTOSAT-1 launched **-** a stereoscopic Earth observation satellite in a sun-synchronous orbit (GG).

__2006__ 1.Google Earth is made available to everyone with an internet connection. A virtual globe program, originally called Earth Viewer, and was created by Keyhole, Inc. It maps the earth by the superimposition of images obtained from satellite imagery, aerial photography and GIS 3D globe (KK).

__2007__ ISRO's CARDTOSAT-2 launched - carries a state-of-the-art panchromatic (PAN) camera that take black and white pictures of the earth in the visible region of the electromagnetic spectrum (GG).

__2008__ 1. Street View integration in GoogleEarth (KK). 2. The potential for 3D holographic visualization becomes real, the applications pertinent to GIS and landscape visualization (LL).

GIS's development has been more evolutionary, than revolutionary. It responds to contemporary needs as much as it responds to technical breakthroughs. Planning and management have always required information as the cornerstone. Early information systems relied on physical storage of data and manual processing. With the advent of the computer, most of these data and procedures have been automated. As a result, the focus of GIS has expanded from descriptive inventories to entirely new applications involving prescriptive analysis. In this transition, map analysis has become more quantitative. This wealth of new processing capabilities provides an opportunity to address complex spatial issues in entirely new ways. It is clear that GIS technology has greatly changed our perspective of a map. It has moved mapping from a historical role of provider of input, to an active and vital ingredient in the "thruput" process of decision-making. Today's professional is challenged to understand this new environment and formulate innovative applications that meet the complexity and accelerating needs of the twenty-first century(17).

__Key principles__
The use of 3-D visualization techniques with GIS historically has been applied for visual impact assessment in natural resource management. In particular, the aesthetics of forest harvest cutblock shape, size and location are of primary importance. However, current GIS technology has not provided visualization functionality affording realistic presentations of the 3-D landscape. GIS based visualization operations are restrictive in their graphic visualization capabilities. Considering the visualization software tools available in the scientific community there has been very little integration of these techniques with commercial GIS software (FORESTRY).

The first step in producing a 3-dimensional representation of geospatial data, is to collect the data itself. This is commonly done by satellite sensors as well as ground based sensors.


 * __Light Detection and Ranging (LiDAR)__**

LIDAR uses ultraviolet, visible or near infrared light to image objects and can be used with a wide range of targets, including non-metallic objects, rocks, rain, chemical compounds, aerosols,clouds and even single molecules. A narrow laser beam can be used to map physical features with very high resolution(O).


 * __Three main components of LiDAR are:__
 * 1) laser transmitter - many different types of lasers exist which are specialized for measurements of specific characteristics
 * 2) a telescope receiver
 * 3) a photo-detector associated with an electronic unit (P)


 * __LiDAR - A process that has three main steps:__
 * 1) A profile of a structure characteristics and compsoition is created by transmitting a laser pulse into the atmosphere or toward the ground.
 * 2) The laser pulse interacts with individual air molecules, particles andéor objects on the Earth's surface (ex. vegetation or the surface of the Earch itself) which may be a result in absorption and scatter of the light in all directions, creating a reduction of the laser beam.
 * 3) The light that is scattered backward toward the LiDAR system is collected by a receiver telecope. The return time of the beam is then detected and the information is processed to provide a usuable LiDAR signal. (P)


 * __Ways that LiDAR can be arranged and configured:__
 * 1) **monostatic arrangement -** the transmitter and reciever are in the same location, most commonly used
 * 2) **coaxial configuration -** the transmitter and reciever axes are the same (as seen in the figure below)
 * 3) **paraxial configuration -** the parallel ray makes a small angle to the optical ray, sometimes used at long range to limit the useful signal dynamics (P)

__**Return Signals of LiDAR**__

Records the first thing the in pulse laser interacts with. A Common example would be the canopy of a forest (as shown in the green data layer in the figure below)
 * First return**

Some on the laser pulse from the LiDAR will travel past the canopy, to interact with the next surface (as seen in the pink data layer in the figure below). May represent additional vegetation layers (i.e.,shrub layer)
 * Second return**

Still, portions of the laser pulse are traveling past the second interaction layer**,** to produce successive data layers representing various layers, and finally, if the vegetation is not too thick, the ground layer. (Q)
 * Multiple returns**



Ground-based lidar technology is based on the travel time of a laser beam between the source(scanner) and the target (outcrop)). Multiple laser beams sweeping the laser range allow creation of a three-dimension (3D) point cloud of the outcropping rock faceat 1-cm resolution. These point clouds are then commonly converted into triangulated surfaces and are used for the draping of high-resolutiondigital photographs to create virtual-reality models of Earth’s surface. **The triangulation step is critical to the quality and accuracy of the final, photo-draped, virtual model. Quality of the virtual-reality model also depends on (1) the density of points and (2) the scanning angle used in the triangulation**. In ideal acquisition conditions, the lidar scan is acquired perpendicular to the outcrop face. The resulting density of points is optimal, and the fi nal triangulated surface has a minimum of holes resulting from acquisition shadows and a minimum of elongated triangles. In diffi cult-to-access outcrops (e.g., a high or remote sea cliff), scanning normal to the outcrop face is commonly not possible. Scans are taken at an angle oblique to the rock face, resulting in a decrease in the density of points available for triangulation. Moreover, data holes or acquisition shadows are more numerous, resulting in a lower quality in the final triangulated model, which will have datagaps and elongated triangles (BB).
 * __Ground Based LiDAR__**



__**Shuttle Radar Topography Mission**__ The Shuttle Radar Topography Mission (SRTM) obtained elevation data on a near-global scale to generate the most complete high-resolution digital topographic database of Earth. SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000.In order to gather topographic (elevation) data of Earth's surface, SRTM used the technique of interferometry. In interferometry, two images are taken from different vantage points of the same area. The slight difference in the two images allows scientists to determine the height of the surface.

__Interferometry__ is the study of interference patterns created by combining two sets of radar signals. If you've ever seen a puddle of water with a film of oil on it, you've probably noticed bands of color on the surface. These bands of color are caused by light rays bouncing off the smooth surfaces of the oil and underlying water, making interference patterns(EE).



SRTM is a fixed-baseline interferometry mission. This means two radar data sets were collected at the same time and the antennas that collected the data were separated by a fixed distance.

Various approaches to visualizing geospatial information in three dimensions have been developed, with different degrees of sophistication and complexity in the underlying technologies. These include:
Visualization for landscape analysis and terrain modeling requires three-dimensional capability, which is not often offered as a built-in function of GIS software. Some GIS packages offer software extenstions for processing and displaying three dimensions (e.g., the triangulated irregular networks (TIN) and 3D analyst extension of ArcGIS). However, the application of the extended function is usually subject to a variety of constraints, including the processing required for generating the TIN, the verticle distortion that must usually be applied to the z-dimension, and the inability to place three-dimensional objects on the model surface (MAYALL). One practical way to make up for the deficiency of GIS for three-dimensional modeling is to take advantage of the three-dimensional modeling capability of CAD systems. For example, consider a method that combines GIS and CAD technologies for visualizing two-dimensional landscape data in three-dimension scenes (as seen in the figure below).This method may be enhanced for visualizing actual changes in the landscape as a well as the impacts of changes in building codes and engineering standards on the landscape. predictive modeling of changes in economic behaviour, ecological succession, and wave erosion may also be implemented.
 * __Using GIS in conjunction with CAD systems__**



__**Linking GIS to statistical software**__ This approach combines the use of a GIS and a statistical software package. In such a system, the GIS serves as the graphical front end for the display of visualization data and the statistical is the data exploration engine. Logically, in between these two components is an application programming interface (API) that is established to facilitate the transfer of data and commands between them. A commercial product built based on this approach is S+ ArcView for GIS developed by MathSoft in 1998, now known as Insightful Corperation (refer to the figure below). This package is based on S-PLUS, a popular statistical package for electronic design automation and modeling of three broad classes of spatial data: geostatistical data, point patterns, and lattice data. Using an interface known as S + API, the statistical and graphical functions of S-PLUS are integrated with the spatial visual capabilities of ArcView. The user can seamlessy export ArcView data to S-PLUS for spatial statistical analysis and then return the graphics and analytical results to ArcView for display. Within the ArcView environment, the user can also directly access S-PLUS objects to obtain information to plot a map with with residual value, add a table, or add an event theme (TEXT).



__**Linking GIS to visualization Software**__ A variety of visualization tools have been developed by the reseach community and made available to the public. While many of these tools brovide basic three-dimensional rendering capabilities, not are not tightly integrated with GIS softwar, which will enable them to use georeferenced data in the operational environment in, for example, forest management. Virtual Forest, developed by Innovative GIS Soultions, Inc., is one of the attempts to integrate the advanced rendering cababilities of visualization software with the geospatial data that is tightly coupled with two independent visualization interfaces: the Tree Designer, and the Landscape Viewer. The Tree Designer allows the user to interactively create and edit tree objects. The Landscape viewer, on the other hand, provides the tools necessary for rendering three-dimensional objects created by the Tree Designer. The rendering techniques provided by the Landscape Viewer include the definition of a DEM view, DEM suface texturing, tree stand boundaries, tree rendering, the conditions of light source and the sky, as well as atmospheric effects. Through a sperate interface, Virtual Forest provides the capability for the user to define landscape views with seperate themes denoting specific visualization events. This allows the user to represent multiple landscape visualization scenes such as different alternatives for harvest cutblock design and temporal events for time-scales (Buckley).



__**Using stand-alone Visualization Software**__ There is now a host of spatial data visualization software packages on the market. Some of these are commercial products and others are public domain products developed by academic institutions or government agencies. These products run on different hardware platforms and are designed for different application areas, particularly for landscape analysis in forestry management. In most cases, these visualization software products are capable of generating high quality scenes that serve the interpretive use of visualization well. However, these products in general also suffer from a number of deficiencies, such as poor or weak linkage between different applications of visualization, the absence of mechanisms for testing the validity and reliability of the visualization scenes, as well as the lack of integration with GIS data models/databases (Buckley).



This is the newest and most exciting development of the visualization of geospatial information. Recent developments in the Internet provide a less expensive alternative tool, which is called the Virtual Reality Modeling Language (VMRL), for building virtual GIS. The VMRL is an open, extensible, industry-standard scene description language for three-dimensional scenes on the internet. With the VMRL, it is possible to create and view distributed, interactive, worlds that are rich with text, images, animation, sound and video. Since the internet is based on the client/server architecture, all CPU-intensive data analysis and rendering processes in virtual GIS can be carried out on the server side, and the resulting three-dimensional worlds can be viewed on any client computer with a web browser that supports the VRML standard (TEXT).
 * __Dynamic visualization via the internet__**



New technologies like the High-Definition survey (HDS) equiptment (also known as 3D laser scanning) appear to offer a substantial time saving method to capture the "as built" environment. HDS is a LiDAR scanner on a tripod and the points it generates from its laser striking objects can be used to construct existing features.

Supporting techniques for improving visualizaitions and interaction with 3s geo-data, e.g., putting textures on objects and facilitating navigation through the 3D environment. VR is a realistic representation of data (2D, 2.5D and 3D), which means that details and physical properties are represented highly realistically even together with sounds and behaviors of the objects. Manipulation and interaction in the views can take place by mouse click, animations, navigation, and exploration. In VR a user explores and navigates in the real world augmented by computer-generated data (Y).
 * __Vitual Reality and Augmented Reality__**

media type="youtube" key="W3dz2xpCJVU?version=3" height="360" width="640" align="center"

__Applications in environmental monitoring and analysis__
3D Laser Mapping offers a range of mobile, fixed and laser systems that can be used for site surveys, perimeter security, research and exploration. 3D Laser Mapping has, for example, developed an innovative remote-controlled laser mapping vehicle called 3DR1 for use underground where mine entry is unsafe (OO).
 * Mining**

The application of mining 3D GIS stimulation system should have characters such as follows: 1) Surface subsidence environment (including surface features, stratum, lager geologic conformation) 3D realistic environment and multiple angles observe; 2) Stimulation and dynamic solid display of the course thatground movement and deformation will change along with mining faces extended; <span style="font-family: 'Arial','sans-serif'; font-size: 13px;">3) Section solution and display any direction of subsidence basin; <span style="font-family: 'Arial','sans-serif'; font-size: 13px;">4) Movement and deformation calculation of any point in rock and on the surface; <span style="font-family: 'Arial','sans-serif'; font-size: 13px;">5) 3D distributed form and volume measure of overlying strata caving zone and fissured zone in pit mining; <span style="font-family: 'Arial','sans-serif'; font-size: 13px;">6) Automatic measure of subsidence area volume; <span style="font-family: 'Arial','sans-serif'; font-size: 13px;">7) Automatic subdivision of land reclamation in subsidence area and rate range of ecological restoration. (NN)



Allow surface constraints on subsurface operations such as seismic, drilling and production to be assessed through visual interpretation within a GIS or mapping environment (PP).
 * Oil And Gas**




 * Flood/Disaster Planning**

Unfortunately, disasters happen. They can be limited in scope or reach catastrophic proportions. They can hit rural, isolated areas as well as sweep through multiple jurisdictions, affecting lives, property, and the environment. To prepare for these events, communities hold emergency preparedness exercises. An emergency preparedness exercise is a simulation of an event, or series of events, designed to test emergency response systems. Communications, technology, existing resources, knowledge, and skills are tested to see if the systems work. Hopefully, the systems will work flawlessly, but sometimes investments need to be made for improvements. In the end, an exercise gives valuable information that can be used to enhance emergency services. In GIS it is essential to have existing geographic datasets information—including hospital capacity, live weather, and traffic—could displayed in near year time (PP).

Forestry professionals and researchers have been investigating visualization techniques for many years addressing a variety of forest management problems. Historically, "artist renderings" were used to communicate the effect of land management activities. Recently, there has been considerable research into applying computer visualization techniques, however very little of this research has found its way into production forestry operations, or integrated with the use of GIS technology for forest planning(FORESTRY).
 * Forestry Management**



Forestry visualization software __should contain the following key functional capabilities__ in order to support realistic rendering capabilities: >> Public domain visualization software applicable for forestry:
 * 1) <span style="color: #000000; font-family: Arial,sans-serif;">3-D object design tools (a tree designer) allowing foresters to build custom tree symbols based on characteristics (e.g. tree type (solid versus wireframe), tree color, percent maturity, size (height) at a specific stage of maturity, hierarchy level of branching, degree of randomness for branching, density and distribut <span style="font-family: Arial,sans-serif; font-size: small;">ion of leaves, and inte rnal and external shadowing.)
 * 2) <span style="background-color: #ffffff; color: #000000; font-family: Arial,sans-serif;">3-D object rendering such as trees;
 * 3) <span style="color: #000000; font-family: Arial,sans-serif;">3-D object //<span style="color: #000000; font-family: Arial,sans-serif;">extrusion //<span style="color: #000000; font-family: Arial,sans-serif;"> to support polygonal and point data rendering (e.g. buildings, light poles, etc.);
 * 4) <span style="background-color: #ffffff; color: #000000; font-family: Arial,sans-serif;">simulation of atmospheric effects (e.g. sky, fog and haze);
 * 5) <span style="background-color: #ffffff; color: #000000; font-family: Arial,sans-serif;">texture mapping to support realistic rendering of polygonal features (e.g. roads, foreground, harvested blocks, water, etc.) and background (e.g. sky and haze);



3D visualization models have a variety of applications in geography and urban studies: site location analysis, emergency facilities planning, design review, marketing, etc. While they are generally used to simply visualize the built environment, there are early signs of them being used as 3D interfaces to more sophisticated simulation models (QQ).
 * Urban Planning**

A general classification of 3D city models, based on their operational purposes, might be organized around four main types:


 * 1) 3D CAD (computer aided design) models of cities
 * 2) Static 3D GIS (geographic information systems) models of cities
 * 3) Navigable 3D GIS models of cities
 * 4) 3D urban simulation model (QQ)

__Issues, concerns, and limitations__
3D GIS developments are mainly in the area of visualization and animation. Bottlenecks for commercial implementation of 3D GIS are as follows:
 * 3D editing is GIS is not yet possible and is traditionally a functionality that is well supported in CAD software but not GIS
 * There is poor linkage between CAD, traditionally designers of 3D models, and GIS.
 * Methods to automatically reconstruct 3D objects are lacking
 * Visualization of 3D information requires special techniques; characteristics such as physical properties of objects (texture, material, color), behavior (e.g., on-click-open), and different levels of detail representations need to be maintained and organized in database management systems.
 * Virtual Reality and Augmented Reality techniques should be incorporated in GIS software to improve interaction with and visualization of 3D environments.

__Comparative analysis against alternative technologies or solutions (Strengths vs Weaknesses)__


__**Using the generic display function of GIS software**__ Presentation of spatial information is a generic function of GIS software. In general, however, this function is not adequate for the purpose of visualization. The display function of GIS software is designed primarily for static two-dimensional views. Three-dimensional display capability is either absent or very limited. The capability to represent flows or movements, is also largely unavailable. However, these constraints of the generic display function do not mean that it cannot be used for visualization. It is possible to use macrogrograms, such as Arc Macro Language (AML) of Arc Info, to develop very powerful visualization applications (BATY). In this approach, the display function of the GIS is used to display maps quickly and effeciently. The macroprograms serve as the link between the graphics and the modeling routines. **The advantages** of using GIS include the use of its own data sources (and therefore removing the need for data conversion), the generality of the user interface, as well as the flexability in coupling with the data anaysis and modeling modules(BATTYZ). **The major weaknesses** to such an approach include the limitation of the generic display function to two-dimensional static views as well as the high requirement for the user to have access to a high level of proficiency in macroprogramming.

__**Benefits of accurately corrected imagery for use in ArcGIS**__ Poor imagery registration limits GIS user’s ability to efficiently perform simple change detection and feature extraction tasks. With GeoImaging Tools for ArcGIS, you can achieve automated and highly accurate image registration. Image registration limits a GIS user’s ability to accurately identify changes in multi-temporal data. By achieving high levels of image registration accuracy, GIS users can extract features and identify changes in imagery.

__Key research hubs__
The research in 3D GIS is intensive and covers all aspects of the collecting, storing and analyzing real world phenomena. Among all, 3D analysis and the issues related (topological models, frameworks for representing spatial relationships, 3D visualization) are mostly in the focus of investigations.

[[image:eas351virtualreality/New-esri-logo.jpg align="right"]]
__**Environmental System Research Institute (ERSI)**__

A software development and providing GIS software and geodata basemanagement applications. The headquarters of Esri is in Redlands, California. The company was founded as Environmental Systems Research Institute in 1969 as a land-use consulting firm. Esri products (particularly ArcGIS) have one-third of the global market share. In 2002 Esri had approximately a 30 percent share of the GIS software market worldwide, more than any other vendor (S).

__ **Zuse-Institut Berlin** __

A research institute for applied mathematics and computer science. Research and service is driven by the principle "Fast-Algorithms - Fast Computers": Provider of solutions for complex problems in science, engineering, environment and society - solutions that often require innovative approaches. (T)

__ **Delft University of Technology, GIS Technology Section** __ Also known as ** TU Delft **, is the largest and oldest Dutch public technical unversity, located in Delft, Netherlands. With eight faculties and numerous research institutes it hosts over 16,000 students, more than 2,600 scientists (including more than 200 professors),over 2,000 doctoral students and more than 2,000 people in the support and management staff. (U)

__ **Department of Geoinformatics, Universiti Teknologi Malaysia** __ The focus of Geoinformation research done at the Univerity Teknologi Malaysia can be broken into three catagories:
 * 1) Algorithm Development
 * 2) System Development
 * 3) Hardware Development[[image:eas351virtualreality/Untitled.jpg align="right"]]

<span style="font-family: Verdana,Arial,Helvetica,sans-serif;">Strategies to develop scientific research products include
 * <span style="font-family: Verdana,Geneva,sans-serif; font-size: 11px;">Take opportunity to using research grants from Ministry of Science (e - Science -Fund, e-Techno-Fund and e-Inno-Fund) to Geoinformation research.
 * <span style="font-family: Verdana,Geneva,sans-serif; font-size: 11px;">Take opportunity to using fundatamental research grant (FRGS) from MoHE to benefit Geoinformation research.
 * <span style="font-family: Verdana,Geneva,sans-serif; font-size: 11px;">Take opportunity to using others research grant to benefit Geoinformation research. (V)

__ **Swiss Federal Institute of Technology (ETH Zurich)** __ ETH Zurich engages in basic research founded on scientific findings and in problem-solving research of lasting value. The society in the 21st century expects new findings in the between humans, technology and nature and technical innovation with added value. The interdisciplinary research conducted at ETH Zurich sets pointers for sustainable development worldwide. The university is a dependable partner for economy, politics and society.

__ **Holografika** __ <span style="display: block; font-family: arial,sans-serif; text-align: left;">The company at present develops and sells 3D display systems. It started selling its 26” and 32” HoloVizio 3D displays in 2004, and plans to offer larger-scale holographic projection systems soon. Second-generation displays, a 3D camera system and a full 3D software environment are all under development. The research and development activities focus on developing next generation holographic 3D displays and inherent 3D applications. The company has established important partnerships and cooperation with large international players like BAE Systems, Shell, Peugeot-Citroen, Thomson, Philips, Videoton, Sony and important European IT companies and institutes like CRS4, CS, Inria, etc. (W)

<span style="background-color: #ffffff; display: block; font-family: tahoma,verdana,arial,helvetica; font-size: 11px; text-align: left;">__ **Solid Terrain Modeling Inc** __ STM can provide a custom model of any spot on earth, work with most data formats and build virtually any size model. If clients don't have the data for their area of interest, STM has access to all major data sources and can prepare the data sets for the project. Any combination of aerial photographs, satellite imagery, maps, pictures, graphics and text can be printed on a model. Architectural and stylized elements are also available to enhance model applications. (X)

__Current trends, vendors and solution providers__
The need for 3D information is rapidly increasing. Currently, many human activities make steps toward the third dimension, i.e. urban planning, cadastre, environmental monitoring, telecommunications, public rescue operations, landscape planning, transportation monitoring, realestate market, hydrographical activities, utility management, military applications (R) .In addition to the changes in the processing environment, contemporary maps have radical forms of display deyong the historical 2d planimetric paper map. Today, one expects to be able to drape spatial information on a 3d view of the terrain. Virtual reality can transform the information from pastel polygons to rendered objects of trees, lakes and buildings for near photographic realism. Embedded hyperlinks access to actual photos, video, audio, text and data associated with map locations. Immersive imaging enables the user to interactively pan and zoom in all directions within a display (17).

There are few commercial-of-the-shelf (C.O.S.T) systems that can be categorised as systems that attempt to provide a solution for 3D representation and analysis. __Four systems__ are chosen for detailed consideration, because they constitute a large share of the GIS market and provide some 3D data processing functions.
 * __3D GIS in the market__**

http://www.esri.com/software/arcgis/extensions/3danalyst/index.html
 * **ESRI - 3D Analyst of ArcGIS**

ArcGIS 3D Analyst, ESRI: The 3D Analyst (3DA) is one of the modules available in ArcGIS GIS.ArcView is designed to provide stand alone and corporate wide (using client-server networkconnectivity) integration of spatial data. With 3DA one can manipulate basically 2.5D data such as surface generation, volume computation, draping raster images, terrain inter-visibility from one point to another. The system works mainly with vector data. Raster files can be incorporated into 3DA, but only for improving the display of vector data. ESRI has further developed the 3D Analyst for the ArcGIS 10 environment (see video below). ArcGIS consists of the Desktop and Workstation components. The Desktop component is based on personal computer (PC) and Microsoft Windows operating system, while the Workstation component is available for both PC and UNIX platforms (R).

media type="youtube" key="LqOkBvQ3cCA?version=3" height="360" width="640" align="center"

http://www.erdas.com
 * **ERDAS - Inc.Imagine VirtualGIS**

It is worth mentioning that the Imagine system was originally developed for remote sensing and image processing tasks. The recently provided GIS module is called VirtualGIS and supplies some 3D visual analysis tools. It is a system that has an emphasis on dynamic visualisation and real-time display in the 3D display environment. Interesting 3D visualisation features of the system are: 1) the possibility to include rapidly 3D models in a selected polygon or along a line (e.g. 3D models of trees in a forest area) and 2) the logo layer that can accommodate a 2D image into the 3D scene and stretch it over the entire view as foreground. Besides these and other extensive 3D visualizations, the system also provides fly-through capabilities as seen in the video below(R).



media type="youtube" key="xDqumshRkAk?version=3" height="360" width="640" align="center"

> http://www.integraph.com GeoMedia Terrain is one of the subsystems that work under the GeoMedia GIS. The system runs under the Windows operating systems. The Terrain system performs three major terrain tasks, namely, terrain analysis, terrain model generations, and flythrough. The navigation tool ActiveFlight provides the three most common navigation modes -free flight, constant above ground elevation and terrain avoidance. It also offers the ability to save and restore viewpoints.
 * **Intergraph Inc. -GeoMedia Terrain**



media type="youtube" key="A20U3TZQu8s?version=3" height="360" width="640" align="center"

> http://www.pcigeomatics.com GeoImaging Tools for ArcGIS provides ArcGIS users a suite of tools for processing and analyzing imagery in the GIS. PCI Geomatics is introducing a suite of modules that integrate directly into ArcGIS for achieving common image related tasks.
 * **PCI GEOMATICS - GeoImaging Tools**

media type="youtube" key="eeaHFI3zo98" height="360" width="640" align="center"

http://www.maps.google.ca A web mapping service application and technology provided by Google, free (for non-commercial use), that powers many map-based services, including the Google Maps website, Google Ride Finder, Google Transit, and maps embedded on third-party websites. It offers street maps, a route planner for traveling by foot, car, bike or public transport and an urban business locator for numerous countries around the world. Google Maps satellite images are not updated in real time; they are several months or years old.
 * **Google Inc - Google Maps**

media type="youtube" key="S5T3sfWnaGg?version=3" height="360" width="640" align="center"

__Future trends__
Driven by military, computer gaming, landscape planning, tourism, and public user demand, photorealism is quickly becoming the norm (DD).
 * Advancements in computer graphics**


 * 4D GIS (XYZ and time) is the next major frontier**. Currently, time is handled as a series of stored map layers than can be animated to view changes on the landscape. Add predictive modeling to the mix and proposed management action (e.g., timber harvesting and subsequent vegetation growth) can be introduced to look into the futute. Tomorrow's data structures will accommodate time as a stored dimension and completely change the conventional mapping paradigm (17).

__**3D GIS: A Future Vision - Striving for comlete GIS integration**__ Imagine a public meeting where a proposed building is added to a virtual, GIS-enabled landscape. The GIS immediately evaluates the new building for compliance with use constraints as well as setback and height restrictions. The water and waste water systems are connected to the outside lines (GIS layers) to verify capacity availability. Stormwater run-off from the roof and other new impermeable surfaces are evaluated and summarized. Security and emergency vehicle access (including turnaround space) are conidered from all access routes. Finally, the reviewers can evaluate the appearance and comparability of the new structure from any vantage point within the existing virtual environment. By substituting larger tree models for the initial planting stock, it is possible to anticipate the appearance of the area some time in the future. Consider and untapped resource - Highschool CAD and computer animation students who might jump at the chance to create 3D environments. For years the geospaial community has worked to bring GIS to the K-12 age group. This audience has grown up with computer games and the use of 3D game-like environments to facilitate learning and community involvement would seem like a natural match.

__Links__
http://eas351virtualreality.wikispaces.com/

http://eas351-ualberta.wikispaces.com/Environmental+Applications+of+Lidar

http://eas351-ualberta.wikispaces.com/3D+Visualization+in+GIS

__References__
__Banner images taken from__ http://blog.appassure.com/wp-content/uploads/2010/07/computers-globe.jpg last accessed Nov 21 2011 http://olliebray.typepad.com/.a/6a00d8341eb53c53ef013487415ac5970c-500wi last accessed Nov 21 2011

(TEXT)Lo, C.P., Yeung A.K.W. (2007), "Concepts and techniques of geographic information systems 2nd Edition" __Pearson Education, Inc.__ ISBN: 0-13-149502-X

(1)http://maps.unomaha.edu/Peterson/gis/Final_Projects/1996/Swanson/GIS_Paper.html accessed: Nov 19 2011

(2) http://www.nwgis.com/gisdefn.htm accessed: Nov19th 2011

(3) http://searchcio-midmarket.techtarget.com/definition/virtual-reality accessed: Nov 19th 2011

(4)Coates, G. (1992). Program from Invisible Site—a virtual sho, a multimedia performance work presented by George Coates Performance Works, San Francisco, CA, March, 1992.

(5)Greenbaum, P. (1992, March). The lawnmower man. Film and video, 9 (3), pp. 58-62.

(6)Krueger, M. W. (1991). Artificial reality (2nd ed.). Reading, MA: Addison-Wesley.

(7) http://www.businessdictionary.com/definition/Virtual-Reality-Modeling-Language-VRML.html accessed: Nov 19th 2011

(8) http://en.wikipedia.org/wiki/3D_rendering accessed Nov:19th 2011

(9) John A Stankovic (1992) RealTime Computing

(10)Computer-Aided Design In CAD' 04 Special Issue: Product Design, Integration and Manufacturing, Vol. 37, No. 9. (August 2005), pp. 931-940.

(11)http://static.howstuffworks.com/gif/virtual-reality-8.jpg last accessed Nov 21 2011

//(12)http://www.pcmag.com/encyclopedia_term/0,2542,t=render&i=50431,00.asp accessed Nov 19th 2011// last accessed Nov 21 2011

//(13)http://www.terranean.com.au/glossary.htm#lidar// last accessed Nov 21 2011

//(14)http://en.wikipedia.org/wiki/Stereoscopy// last accessed Nov 21 2011

//(15)// http://users.telenet.be/thomasweynants//images/stereoscope/StereoscopeGhost.jpg// last accessed Nov 21 2011

//(16)http://inventors.about.com/library/blcoindex.htm// last accessed Nov 21 2011

//(17)http://www.innovativegis.com/basis/MapAnalysis/Topic27/Topic27.htm// last accessed Nov 21 2011

//(18)http://www.enotes.com/topic/Edwin_Catmull#References// last accessed Nov 21 2011

//(19)http://www.casa.ucl.ac.uk/gistimeline/// last accessed Nov 21 2011

//(20)http://www.esri.com/about-esri/about/history.html// last accessed Nov 21 2011

//(C)Card, S.K., Mackinlay, J.D., and Schneiderman, B. (1999) "Information Visualization," Readings in information Visualization: Using vision to think San Fransisco, CA: Morgan Kaufmann Publishers.//

//(D)Fabrikant, S.I. (2000)8 "Spatialized browsing in large data archives," Transactions in GIS, Vol. 4, No.1, pp. 65-7//

//(E)// //http://www.rockware.com/assets/products/191/features/411/2685/vmpro_det9b.jpg// last accessed Nov 21 2011

//(F)[]// last accessed Nov 21 2011

//(G)// //http://www.comsol.ch/comsol/pub/media/bilder/product_info/splus%20printscreen.gif// last accessed Nov 21 2011

//(H)// //www.innovativegis.com/basis/.../GW_Aug98_visLandscapes.htm// last accessed Nov 21 2011

//(I)// //http://news.gislounge.com/wp-content/uploads/2010/11/PT-SketchUpPTSU1-1024x618.jpg// last accessed Nov 21 2011

//(J)// //http://4.bp.blogspot.com/_7ZYqYi4xigk/TPPlBTxha7I/AAAAAAAAHGs/PCnSsvY4O0E/s1600/streetview3.JPG// last accessed Nov 21 2011

//(K)// //[]// last accessed Nov 21 2011

//(L)// //www.idsoftware.com/business/history// last accessed Nov 21 2011

//(M)// //http://pnmedia.gamespy.com/classicgaming.gamespy.com/images/oldsite/clusterimages/wolf3d2.jpg// last accessed Nov 21 2011

//(N)// //http://www.gamedev.net/index.php?app=core&module=attach§ion=attach&attach_rel_module=ccs&attach_id=2831// last accessed Nov 21 2011

//(O)Cracknell, A. P., & Hayes, L. (2006).// Introduction to remote sensing//. London: Taylor & Francis.//

//(P)A.S. Antonarakisa A.S, K.S. Richards and J. Brasington. 2007. Object-based Land Cover Classification using Airborne LiDAR.// Remote Sensing of the Environment//. 112:616 pp 2988-2998//

//(Q)// //http://www.ndep.gov/USDAFS_LIDAR.pdf// last accessed Nov 21 2011

//(R)Zlantanova, S. et al. (2002) "Trends in 3D GIS development. __Journal of Geospatial Engineering,__ Vol. 4, No. 2, PP.71-80// //http://www.lsgi.polyu.edu.hk/STAFF/ZL.Li/vol_4_2/01_zlatanova.pdf// last accessed Nov 21 2011

//(S)// //[]// last accessed Nov 21 2011

//(T)// //[]// last accessed Nov 21 2011

//(U)// //[]// last accessed Nov 21 2011

//(V)// //http://www.fksg.utm.my/// last accessed Nov 21 2011

//(W)// //[]// last accessed Nov 21 2011

//(X)Zlatanova, S., Rahman, A.A., Pilouk M. (2002) "3D GIS: Current status and perspectives" __Symposium on Geospatial Theory, Processing and Applications__// //[]// last accessed Nov 21 2011

//(Y)Jantien E. Stoter, Petrus Johannes Maria van Oosterom, (2006) "Three Dimension cadastre in an international context" __Taylor & Francis Group__ ISBN: 10:0-8493-3932-4//

//(AA)// //McGaughey, Robert J. 1997. Visualizing forest stand dynamics using the stand visualization system. In: Proceedings of the 1997 ACSM/ASPRS Annual Convention and Exposition; April 7-10, 1997. Seattle, WA. Bethesda, MD: American Society for Photogrammetry and Remote Sensing. Vol. 4:248-257.//

//(BB)// //<span style="color: #20231e; font-family: Arial,sans-serif;">Bonnaffe F., et al. (2007), “A method for acquiring and processing ground-based lidar datain difficult-to-access outcrops for use in three-dimensional, virtual-reality models” __Geosphere__; v. 3; no. 6; p. 501–510 //

//<span style="color: #20231e; font-family: Arial,sans-serif;">(CC) // //http://eas351-ualberta.wikispaces.com/3D+Visualization+in+GIS// last accessed Nov 21 2011

//(DD)// //Brooks, S., Whalley, J.L. 2008. Multilayer hybrid visualizations to support 3D GIS. ScienceDirect Computers, Environment and Urban Systems, 32: 278-292.//

//(EE)// //[]// last accessed Nov 21 2011

//(FF)// // Zhou, GQ., Tan, ZY., Cen, MY., Li, C. 2006. Customizing visualization in three-dimensional urban GIS via web-based interaction. Journal of urban planning and development, 132 (2): 97-103 //

// (GG) // //http://www.mdafederal.com/geocover/project// last accessed Nov 21 2011

//(HH)// //http://rsgislearn.blogspot.com/2007/04/chronology-of-remote-sensing.html// last accessed Nov 21 2011

//(II)// //http://www.filebuzz.com/software_screenshot/full/125024-TerrainCAD.gif// last accessed Nov 21 2011

//(JJ)// //http://en.wikipedia.org/wiki/NASA_World_Wind// last accessed Nov 21 2011

//(KK)// //www.google.com/history// last accessed Nov 21 2011 //(LL)// //http://www.holovisionproject.org/index.php// last accessed Nov 21 2011

//(MM)// //http://www.gdmc.nl/zlatanova/thesis/html/refer/ps/AR_MP_SZ01.pdf// last accessed Nov 21 2011

//(NN)// //Weijia Guo; Bei Jiang; Bo Li;, "Research on 3D GIS simulation system of mining surface subsidence,"// Remote Sensing, Environment and Transportation Engineering (RSETE), 2011 International Conference on //, vol., no., pp.8442-8445, 24-26 June 2011//

//(OO)// //http://www.mining-technology.com/contractors/exploration/3d-laser-mapping/// //last accessed Nov 21 2011//

//(PP)// //http://www.esri.com/mapmuseum/mapbook_gallery/volume25/images/petroleum1_lg.jpg// //last accessed Nov 21 2011//

(BATTY) Batty, M. (1994) " Using GIS for visual simulation modeling," __GIS World,__ Vol.7, No.10, pp.46-48

(BATTYZ) Batty, M. and Xie, Y. (1994) "Urban analysis in a GIS environment: Population density modeling using ArcInfo," __Spatial Analyst and GIS,__ PP.189-219

(FORESTRY) []// last accessed Nov 21 2011