PEMA Aerial Imagery

PA Emergency Management Agency | Statewide, PA

The purpose of this project was to obtain digital, high-resolution aerial imagery for the Commonwealth of Pennsylvania. The digital data will be used for many purposes, especially for use in 9-1-1 call delivery in a Next Generation 9-1-1 environment. The primary goal of this project was to collect new aerial photography and to develop new statewide digital orthoimagery for the Commonwealth of Pennsylvania for the first year (covering 45,500.75 square miles) and to initiate a three-year maintenance cycle of approximately one-third of the Commonwealth each year thereafter.

For this assignment, AEG served as a subconsultant and provided ground survey for accuracy check points at features identifiable in aerial imagery. During the first year of this contract, AEG surveyed 120 QA/QC check points that were widely dispersed throughout all counties in the Western and Central Sectors of Pennsylvania.

AEG’s surveyors were responsible for the final determination of check points. The final selection of the location of each individual check point was determined in the field, by the surveyor, based on local ground conditions and/or access constraints. Care was given to not deviate too far from the pre-selected locations so that point distribution cover was not compromised. Each survey point was surveyed one time, and then 50% of the check points were surveyed a second time. The second observation always occurred at least four hours after the first observation. All repeat observations had to agree with original observations within ±5-cm. Points that did not meet the accuracy requirements were surveyed again until repeat observations were within ±5-cm. GPS survey procedures were used to obtain ellipsoid heights accurate to ±5-cm at the 95% confidence level.

Once all surveys were completed, AEG put together a final Survey Report that was compliant with Pennsylvania Standards of Practice for Professional Surveying and Mapping. The report included a listing of all NGS monuments used, a description of the VRS network used, survey equipment, field survey procedures, and data processing procedures used.