High Resolution 1:10,000 scale Mapping Strategy of Multi ... - NDMA

lessens the effect of topographic relief displacement on raw imagery.
• Preparing 3D Simulations. DTMs are the fundamental data source required for
preparing 3D perspectives and flight simulations. Without DTMs, 3D
simulations cannot be created.
• Analyzing Volumetric Change. Comparing DTMs of a region from different
time periods allows for the computation of volumetric change (e.g., cut and
fill).
• Estimating River Channel Change. Rates of river channel erosion and
deposition can be estimated using DTMs extracted from imagery collected at
various time periods.
• Creating Contour Maps. Contour maps can be derived from DTMs. Using a
series of mass points, contour lines for a given range in elevation can be
automatically extracted.
In general, DTMs are a first generation data product derived from imagery using
the principles of 3D geographic imaging. Second generation data products such as
slope and aspect images, contour maps, and volumetric change analyses can be
derived from DTMs for use in various GIS and engineering applications.
Control for satellite block triangulation
Both GCPs and tie points can be used for satellite block triangulation of a
stereo scene. For triangulating a single scene, only GCPs are used. In this case,
space resection techniques are used to compute the exterior orientation parameters
associated with the satellite as they existed at the time of image capture. A minimum
of six GCPs is necessary. Ten or more GCPs are recommended to obtain a good
triangulation result.
The best locations for GCPs in the scene are shown in Figure below
5. Orthorectification
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