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The Atlantic Group refines surface model information from which contours are generated using ImageStation DTM Collection (ISDC) software on our softcopy photogrammetric workstations. ISDM imports and uses features such as breaklines, ridge lines, drain lines, vertical faults, and elevation points, along with planimetric features such as hydrography, retaining walls, and road edges to develop the DTM. Contours are created by first generating a triangulated irregular network (TIN) surface model. The TIN model is used to interpolate and generate contours at the required contour interval.
Contour generation algorithms are preset within the collection software. Generating contours on a softcopy photogrammetric workstation affords our technicians the opportunity to view superimposed contours directly over a stereo model, in 3-D, and to modify the topographic model before a final DTM surface and contours are generated. This technical approach allows for a more thorough QA/QC of the contour information.
The software also allows our compilation technicians to regenerate quality review contours at any time during DTM compilation and to immediately view the results. In the event that there is an identified anomaly and a need to apply revisions or changes, corrective actions can be interactively applied. The completed DTM is processed to create a Triangulated Irregular Network (TIN) file. This file consists of triangles whose vertexes are located at mass points or at the vertexes of the vectors that define breaklines. As an example, a breakline that is a single line stream will have numerous vertexes that define its shape.
By also serving as vertexes in the TIN file, programmatically derived contours, generated from the TIN, will correctly interact with the stream and logically and positionally “vee” upstream in complete compatibility with the vector-based stream.
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