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Waterways
Mapping
Where are all the waterways?
Maps in many portions of the world are woefully out of date and
in some cases, over 25 years old. Often this leaves users with only
a general understanding of where Lines of Communication (LOCs),
such as waterways, used to be. AAI has significant experience
in using the broad area coverage of Landsat Thematic Mapper (TM)
imagery and other multispectral sensors to extract waterways.
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This Landsat Thematic Mapper image subset
depicts extracted waterways in red.
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This ADRG Map highlights another area with
extracted waterways from a recent multispectral image shown
in purple. Note the stream differences that were derived from
the current image data when compared to the outdated map.
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Application Example
Objective
Waterways serve as a key element in South America's transportation
and communication networks. In a mountainous region of Peru, a US
government agency was interested in finding uncharted waterways/transportation
routes using Landsat TM imagery.
Approach
Working with a series of signatures developed from the large river,
IMAGINE
Subpixel Classifier processed Landsat TM imagery to find locations
of water in smaller rivers and streams.
Challenges
· The region is largely inaccessible
· Ground survey is extremely expensive, time
consuming, and dangerous
· Multiple training sets were required to
develop signatures for a range of water depth
· Area is too vast and mountainous for airborne
imagery to be collected and effectively used for mapping
Solution
IMAGINE
Subpixel Classifier identified hundreds of miles of waterways
using signatures derived from the large river. Other filtering and
interpolation techniques were utilized to generate a comprehensive
map of waterways in the region.
IMAGINE
Subpixel Classifier can identify most any material, in this
case exposed water, if it occupies at least 20% of the pixel. Rivers,
streams and tributaries were identified, even where partially obstructed
by overhanging vegetation, which is so prevalent in this region.
Includes material © Space Imaging
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