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achieve the most accurate possible representation of the ground surface for production <br />of contours and orthophoto production, if needed. Bridges and overpasses will be <br />correctly modeled in 3D. <br />Contours will be generated from the DTM's using Intergraph Siteworks and displayed <br />on the graphics screen of a digital photogrammetric workstation. The operator checks <br />the contour set by viewing it in 3D with digital aerial imagery in the background. <br />Line smoothing programs are used where appropriate to enhance aesthetic quality of <br />the contour strings. Every index contour will be labeled. <br />Digital Planimetric Mapping <br />This task involves extraction and processing of planimetric features from the aerial <br />photography using interactive photogrammetric techniques. Data from field edits will be <br />integrated at this stage as well. <br />• The photogrammetric technicians will digitize all of the planimetric features desired <br />by the City into a MicroStation design (.DGN) file using digital mapping software. <br />Common features are grouped together and placed on predetermined levels in <br />accordance with the City's CADD specification, and assigned their distinguishing <br />lineweights, linestyles and colors. <br />• The planimetric files will be divided into sheets as desired by the City, and carefully <br />reviewed by the QC Technicians for correctness, completeness, and aesthetic quality. <br />The files will also be checked for full compliance with the City's CADD specification. <br />QC checks will be performed with digital imagery in the background, and the <br />planimetric data superimposed, making any missing or incorrectly digitized features <br />readily apparent. Checkplots will be produced as a final step in the QC process. <br />• The preliminary file sets will be written to CD-ROM disks for delivery to the City, <br />together with a set of checkplots. <br />• Upon receiving approval from the City, field crews will be mobilized to perform field <br />edits, cross-sections, supplemental DTM data collection, and any other survey tasks <br />desired by the City. Total station instrumentation and data collectors will be used for <br />this task. <br />• Upon completion of the field surveys, the data collectors will be downloaded, the data <br />processed, and integrated into the MicroStation files with the photogrammetrically <br />captured information. Following final QC checks, the completed MicroStation files <br />will be written to CD-ROM disks for delivery to the City, together with a set of <br />hardcopy plots. <br />Orthorectification <br />This task involves orthorectification of the raw digital raster images that were created by <br />scanning the aerial negatives. A number of image processing techniques are used to <br />maximize the quality of the deliverable images. <br />• The unrectified raster images will be georeferenced to the DTM's using the field <br />control, analytical aerotriangulation and aerial camera data. The digital <br />13