Image Acquisition Overview Resource Mapping -- Remote Sensing and GIS for Conservation

3D Visualization and Landscape Analysis

Section of the Delaware River in New York, at 50 cm-per-pixel resolution.

Combining orthophoto mosaics with their DEMs also facilitates watershed analysis and visualization of the topography by providing three-dimensional views in which slope and azimuth can be measured and water flow rates from those slopes calculated.

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Section of the Delaware River perpendicular to the previous view and river flow.

3D visualization software, such as Google Earth, view combined mosaics and DEMs from different directions and levels of detail, in both false color infrared and natural color. If seen in too much detail though, the draped nature of the image tends to give buildings and cars a slightly melted 'post-holocaustal' appearance.

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ERDAS Stereo Analyst, available as an extension for ESRI ArcGIS and ArcView, uses red/blue-green (anaglyph) or frame-synced Polaroid glasses to display crisp, on-screen, 3D images of the original georeferenced stereo pairs in the block files without the melted appearance. These optical stereo images can be analyzed at large scale with accurate tools to measure slope and azimuth, the size and height of buildings and individual trees, or the average heights and volume of timber stands.

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Image at right requires use of red/blue glasses to view in stereo.

The optical stereo image produced on-screen by this process is limited to a vertical view, but the image is as sharp and detailed as the original photography. It can be directly measured and mapped in Stereo Analyst, or freeware programs like StereoPhoto Maker can be used to convert stereo pairs to anaglyphs that can then be georeferenced in a standard GIS.

Image at right requires use of red/blue glasses to view in stereo.

ERDAS Stereo Analyst works within the georeferenced coordinate space of the imagery's bundle-adjusted block file, delineating elevation, height, and area as points, lines, and polygons in 3D shapefiles. We can thereby measure logging gaps and tree height in forest canopies or calculate slope and aspect to plan potential routes for gas pipe lines. This capacity is critical to the value-added service we provide our clients. We also can train an organization's in-house staff in the use of the software.

©Winrock International reproduced with their permission for illustrative purposes

Image below, left requires use of red/blue glasses to view in stereo.

Vertical stereo measurements of slope and aspect with corresponding 3D view used to plan a 640-kilometer pipe line corridor from Bolivia to Brazil.

 

Using the ERDAS image processing program, a georeferenced terrain can be navigated interactively in ERDAS Virtual World. Then specific 3D optical stereo measurements can be made from a selected site in Stereo Analyst. Lowering the vantage point of the Virtual World 3D viewer to the ground, the virtual landscape can be viewed from human perspective, or a viewshed map can be produced that shows all parts of the surrounding area visible from that position and height.

 

 

From Images .... to Maps .... to Information

Creating photo-based maps and modeling them in three dimensions is a powerful tool for illustrating properties as well as monitoring them. Active computerized illustration makes a better presentation of potential land parcels for conservation than simple maps. We produce property maps with computerized fly-thrus for land trusts and conservation marketing firms such as Landvest, Inc. of Boston, Massachusetts.

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