1:14,400 scale aerial photography with airborne GPS was acquired April 6 to
16, 2004 with a Wild RC-30 aerial camera system. The imagery was scanned at
14 microns directly from the aerial negatives.
The aero triangulation process utilized an airborne gps survey undertaken
during the flight to provided geodetic coordinates and elevation of photo
centers. Also, image targeted ground control points where visible on the
2004 aerial flight and were used as control. Aerial triangulation was
performed using softcopy workstations and Mira Solutions AT bundle
adjustment program, Mira-AT. Details of the aerial triangulation process
can be found in the Suffolk County, New York 2004 Orthophoto Update
Project Aerial Triangulation Report.
For the 2001 orthophoto project only minimum DTM was collected in the
center area of each aerial photo model creating an uneven distribution of
data throughout the project area. This process created what has been called
"donut-holes" in the DTM and limited the usefulness of the data set for
future ortho photo projects and other applications for this level of DTM.
The 2004 project requirement was to fill in these sparse areas of DTM to
create a consistent pattern digital terrain points throughout the project
area. This was done by using a softcopy workstation with the AMSA-Softcopy
program, overlaying the existing DTM on the stereo model and then adding
points or breaklines to create a uniform level of digital terrain data.
During this process the aerial photography was inspected for new roads and
bridges that required collection of a bridge polygon that was used to
correct the shape of the bridge during the orthophoto process. The photo
inspection was assisted by information provided by Suffolk County as to the
location of new roadways since 2001.
The images were then ortho rectified using Mira Solutions Mira Ortho
software. Mira Solutions Mira Mosaic program was used for the mosaicking,
color balancing and tiling of the imagery. During the orthophoto process
Mira Ortho software processed the bridges so one or both sides of an
elevated bridge had a solid black apron created to eliminate any signs of
image smearing. The Mira Solutions process produced the same effect for
bridges as was required to meet the previous ortho photo project. Quality
control was maintained throughout the process using internal QA programs
within the Mira Solutions suite of orthophoto production software.
Final files were then compressed using MrSID. Final deliverables in TIFF
format with TFW files and MrSID files where placed on DVD Media.
Final quality control for horizontal accuracy and image
quality was performed by New York State.