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IMPROVEMENTS OF 36 GRADE CROSSINGS
(Owner: Southeastern Pennsylvania Transportation Authority (SEPTA))
|SEPTA wanted a study on how to improve roadway safety at 36 grade crossings on their Media-Sharon Hill Line. As a Subconsultant for the project, the main objective of BET Consultants was to develop topographic mapping at two different scales (1" = 20' and 1" = 50') by photogrammetric methods.|
Intervisible pair of ground control stations (survey base line) was positioned for each of the crossings for conventional surveys. The coordinates and elevations of these stations were determined by rapid static satellite observations performed in five days. Three Leica dual frequency SR530 receivers were used. Satellite data was downloaded and processed, transformed into vectors using the Leica SKI-Pro Version 2.0 software package. The network was free adjusted, minimally constrained in 3D on WGS'84 ellipsoid using the MOVE3 Version 3.02 software. Final adjustments were done in 3D least squares adjustment using the STAR*NET-GPS Version 5.112. The internal accuracy of the network was checked by computing loop misclosures.
Primary photogrammetric control was established by GPS Real Time Kinematic (RTK) observations. Same Leica SKI-Pro Version 2.0 was used to process the data.