PEMA Aerial Imagery

PA Emergency Management Agency | Statewide, PA

The purpose of this project is 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 intent for this four-year project is 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 serves as a subconsultant and is providing ground survey for accuracy check points at features that will be identifiable in aerial imagery. During the first year of this contract, AEG surveyed 120 QA/QC check points that are widely dispersed throughout all counties in the Western and Central Sectors of Pennsylvania.

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