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Digital Earth > TerravisionTM > User Guide > Creating TerraVisionTM Datasets

8. Creating TerraVisionTM Datasets

This section is provided to give you some information on how you can go about creating your terrain and other datasets for visualization using TerraVision. This involves creating OI (ortho-imagery) pyramids, DEM (elevation) pyramids, digital maps (for the Map Viewer), and VRML models (overlayed on the terrain).

Creating Image (OI) Pyramids

TerraVisionTM uses a tiled, multi-resolution pyramid to store all of its imagery and elevation data (see the image above). SRI International provide a command-line utility for creating this structure from raw bitmap imagery. This utility is called make_oi.

make_oi is part of the tsmApi library tools archive. You can download the latest tsmUtils archive for various platforms from the tsmApi Download Page. Using make_oi, you can create an OI pyramid from raw source imagery. Currently we only support raw RGB bitmaps and PPM/PGM format images. Please refer to the make_oi Manual Page for information on how to use this utility. As an example, the following command-line is used to create an OI dataset called laguna_beach.oi from the source 2.4384 m resolution PPM image, and supplying the UTM coordinate of the lower-left corner of the image. The geoname is a string that is used to associate an OI pyramid with a DEM pyramid.


  make_oi ~magic/TileSets/Pyramids/laguna_beach \
          laguna_beach.ca.ppm \
          -ll_e 417945 -ll_n 3708247 -zone 11 \
          -startres 2.4384 -geoname "Laguna Beach"
N.B. through convention, TerraVisionTM datasets are stored in a directory called Pyramids, which is often a subdirectory of a directory called TileSets.

Creating Elevation (DEM) Pyramids

The process for creating DEM pyramids is very similar to that of creating an OI pyramid. SRI International provide a utility called make_dem as part of the tsmApi library tools archive. You can read the make_dem Manual Page for information on how to use this utility.

As an example, the following command-line is used to create a DEM dataset called laguna_beach.dem from the source 78.0288 m resolution raw (32-bit) elevation bitmap, which has 160 x 198 postings, and supplying the UTM coordinate of the lower-left corner of the image. Note that we specify the same geoname for the DEM as in the OI example above. This lets TerraVisionTM know that these datasets should be treated as an (imagery, elevation) pair.


  make_dem ~magic/TileSets/Pyramids/laguna_beach \
           laguna_beach.ca_dem.raw \
           -width 160 -height 198 \
           -ll_e 417945 -ll_n 3708247 -zone 11 \
           -startres 78.0288 -geoname "Laguna Beach" 
There are no constraints placed placed on the relation between the OI and the DEM data, other than that the DEM dataset should over the OI dataset. However each dataset can be in different coordinate systems, of different resolutions, and with different lower-left origins.

Creating GeoVRML Models

TerraVisionTM can overlay GeoVRML models on top of the terrain, e.g. buildings, atmospheric simulations, roads, etc. In order to create a VRML model that TerraVisionTM can use, you need to create a directory with a .model extension. Although it is not necessary, it is good practice to use the same root name as the dataset.

Inside this directory there must be a file called model.wrl. This is the GeoVRML model for the particular feature you want to represent. This file can Inline other files as required.

GeoVRML is used because it can specify the exact geographic coordinates of features. The GeoVRML 1.0 specification can be found from the GeoVRML Home Page. You may supply an optional GeoMetadata node to provide information such as author, copyright, etc. For example,


#VRML V2.0 utf8
....
GeoMetadata {
  summary [
    "title"       "McKenna MOUT Buildings"
    "description" "Building models for the MOUT site at Ft Benning, GA"
    "originator"  "Aaron Heller, SRI International"
    "copyright"   "(C) SRI International, 1998. All rights reserved."
  ]
  data USE GEOLOC
}
....

Creating Digital Maps

TerraVisionTM has a Map Viewer which lets you view digital maps and treat these as active maps. This means that you can click on the map and your 3-D (or 2-D) viewer will move to that location. Also, you can overlay the view frustum or flight path from your 3-D viewer on the map.

In order to associate a map image with a dataset you need to create a directory with a .map extension. Although it is not necessary, it is good practice to use the same root name as the dataset.

Inside this directory you need two files: one for the image data and one for the metadata about the geographic extent of the map image. The image can be in PPM, GIF, or JFIF/JPEG format, and can be given any name. The metadata file must be called map.info. The map.info file contains the filename of the image as well as the (u,v) coordinate of the lower-left and upper-right corner of the image. (u,v) are specified in the same coordinate system as the OI and DEM datasets that the map is being associated with. For example,


  # ---- map.tspec ----
  map-name "fort-irwin-utm.ppm"
  map-geoname "Ft Irwin (2scene)"
  map-min-u 520000
  map-max-u 570000
  map-min-v 3880000
  map-max-v 3920000
This map.info file specifies that there is a file called fort-irwin-utm.ppm in the same directory, and that it's lower-left UTM coordinate is (520000, 3880000), and it's upper-right UTM coordinate is (570000, 3920000). The map-geoname field is used to associate this map with a particular OI dataset - it should match the geo-name field in the OI's tile.tspec file.

 

 

Copyright ©2000 SRI International. All rights reserved.

For more information, please contact: digital-earth@ai.sri.com.
Last updated: Monday, 17-Sep-2001 10:03:44 PDT.