Geist Software Labs has developed software tools to create real-time 3D terrain models using Landsat 7 satellite images and digital elevation models. The tools support all of the steps necessary to model any region of the earth surface, from tiling satellite images and generating triangle meshes to rendering the landscape and building virtual reality applications.

 

Step 1 - Select Elevation Data and Satelite Images

The first step in creating a landscape model is to acquire the digital elevation files and Landsat 7 images of the desired area. So far, Geist3D has been tested with the data published by the Canadian Council of Geomantics at www.geobase.ca. The site contains a consistent dataset covering all of the Canadian landmass and coastal regions at 17-23 meter spatial and 15 meter spectral resolution. It also features an intuitive interface to select and download different geographical regions.

After pointing Geist3D to a directory containing content retrieved from geobase, a 2D map shows the corresponding coverage of the satellite images and elevation files. The interface indicates where the satellite images overlap and which spectral bands are present for each tile, including the high resolution panchromatic band. Using simple mouse operations a user can further refine the area by excluding elevation files and satellite images.

 

 

Step 2 -Tile Satelite Images and generate 3D Landscape

Out of the seven Landsat spectral bands, three are chosen as the RGB components of the terrain surface. Due to varying atmospheric conditions and camera settings, adjacent tiles may display different spectral shift and scale. Geist3D therefore provides an interactive interface to zoom into the overlapping regions of neighboring tiles and apply histogram operations until the desired color correlation has been achieved.

A subsequent preprocessing step merges the digital elevation data and satellite images into one large file containing a quad-tree of triangle patches which cover the terrain. Each vertex contains elevation and color information, and the each level of the quad-tree models the landscape at a different level of detail. Subsequent levels are smoothed to ensure seamless transitions.

The spatial resolution at the highest level of detail is between the 17-23 meters of the original elevation data. If the panchromatic Landsat 7 bands are present, then the satellite images are sharpened from 30 meter resolution to approximately 15 meters, resulting in a unique color for every vertex.

 

Step 3 - View 3D model and develop applications

The Geist3D graphics engine is capable of rendering the quad tree generated in the preprocessing step in real time at interactive frame rates. Users can freely navigate the environment at high velocities and examine the landscape from any viewpoint at the surface or from space. The terrain rendering component generates realistic reflective water and performs accurate lighting calculations using OpenGL shading programs.

Geist3D also contains a development environment to create a variety of virtual reality applications using 2D user interface widgets, a fast scripting language, different types of 3D cameras and sensors as well as third party 3D models and animations. The development environment was recently used to build a viewer for the Canada Coast Watch simulation test bed developed in a joint project by several Canadian Universities and the Department of Defense.

 

All of the images on this site are real time screen shots of the of a terrain model covering the entire coastal region of British Columbia. The following links lead to additional AVI movies compressed using the Xvid codec.

 

 

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