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Johnson -Frank & Associates Inc. <br />(AB) Surveying & Mapping Services <br />City of Santa Ana <br />Orthorectiticatlon <br />This task involves orthorecti fi cation of the raw digital raster images that were created by scanning <br />the aerial negatives. A number of image processing techniques are used to maximize the quality of <br />the deliverable images. <br />• -The unrectified raster images will be georeferenced to the OTM's using the field control, <br />analytical aerotriangulation and aerial camera data. The digital orthophotography will be <br />created by draping the unrectified raster images over their corresponding digital terrain <br />models. All relief displacement .will be removed from the raw image files at ground level <br />on a pixel -by -pixel basis, yielding a set of orthorectified digital photo images. <br />• Mosaicking will be performed to ensure a perfect edge match between all orthophoto <br />sheet tiles. Creation of seam lines is performed interactively to ensure that no image <br />flaws result from seam lines passing through tall structures. <br />• Radiometric adjustment will be performed to balance and match color tones, brightness <br />and contrast of the imagery over the whole project. Histograms will be applied on a <br />project basis and not just to adjacent tiles, ensuring uniformity of tone over the entire <br />image database. Image editing soflivare will be used to repair any minor flaws on the <br />imagery. <br />• The imagery will be tiled into sheets as desired by the City. The digital orthophoto <br />software will be instructed to output a .COT file for each orthophoto tile. The completed <br />image data set will be written to CD-ROM disks for delivery to the City. Images will be <br />delivered in the format selected by the City, including .ecw files ifrequested. <br />Ground / Field Topographic Surveys <br />This task involves the survey and data collection of any features to be picked up by crews in the <br />field. <br />5ISO E. Hunter Ave. 18 Anaheim, CA 92807 <br />17141 777-8877 alanfrank(a7lnhnson-frank.eom FAX_ (714) 777-1641 <br />