Aerial Photogrammetric Photography and Topographic Map Update Services

The Vendor is required to provide for aerial photogrammetric photography and topographic map update services
- Aerial Photography
•    Obtain aerial digital photography covering the identified area (figure 1a) suitable for digitizing and plotting of 2’ contours at 1”=200’ scale. 
•    The photography must be taken on a sunny day when there is minimal foliage and no snow cover (prefer early spring). 
•    The photography must have sixty (60) percent net forward gain and thirty (30) percent sidelap, plus or minus five (5) percent. 
•    Negative scale of film photography is not to exceed 1”=800’ and capture resolution of digital photography will not be lower than 0.5’.
•    If a digital aerial camera system is used, it must be a large format (capture width at least 12,000 pixels across track) system with an usgs manufacturer certification and manufacturer calibration. The digital camera system must also have precisely determined orientation geometry and must fully support stereo photogrammetric mapping with a high level of horizontal and vertical accuracy.
•    Provided with one set of original black and white contact prints of the film camera exposures or high resolution prints of the digital camera imagery.
•    All film camera negatives and diapositives (if applicable) and all digital camera raw images are considered property of county.
•    County will be provided with a digital orthophoto of the area defined in task 1d. 
•    The digital orthophoto shall be at a 1” = 100’ scale and have a maximum pixel size of 0.5’. 
•    The digital orthophoto shall be provided on compact Disk (CD) in both TIFF and JPEG format.
- Base Map Development
•    Portions of the three base maps were updated photogrammetrically annually from 1994 to 2025. The revised 2025 digital maps were prepared in AutoCAD 2025 and saved on a flash drive. A description of the drawing layers can be found in table 1.
•    The county commissioned a digital topographic map of the area in the vicinity of the landfill. The approximate area mapped is shown on figure 1a. This original map was prepared using photogrammetric methods and AutoCAD release 10. The complete base map was digitized by breaking it into the three subareas shown on figures 2a (subarea 1), 2b (subarea 2), and 2c (subarea 3). A fourth map, figure 3, was prepared to detail an area of figure 2b on a 24"x36" sheet.
•    The original maps were prepared using ground control established in 1991. Ground control information is provided in a specific layer on the digital maps.
•    The combined acreage of the areas outlined on figure 3 is approximately 250 acres. These areas are only approximations and the county reserves the right to increase or extend the changed areas after we have reviewed the aerial photographs. If the actual acreage mapped exceeds the original estimate by more than ten percent (i.e. Greater than 20 acres), the county will pay contractor an additional sum equal to the number of acres over the original estimate times a unit price per acre. The unit price per acre will be the bid price for this task divided by the original estimate of 250 acres.
•    The 2025 digital maps include a separate layer depicting approximately 115 monitoring well locations. The county resurveys many of these locations annually and will provide new coordinate information to contractor each year.
- The four updated maps must be provided in separate, digital, AutoCAD 2010 format files on a read only Compact Disk. Provide three copies of the Compact Disk.
- Provide five copies of a final color paper plot of the Detail Map at a 1" = 200' scale. Each plot should be on a 24" x 36" sheet with the north direction oriented parallel to the short dimension.

- Contract Period/Term: 3 years
- Questions/Inquires Deadline: October 20, 2025