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Horizontal and Vertical Control Surveys
Souder Miller Surveyors are experienced in providing precision horizontal and vertical control surveys for aerial mapping, engineering projects and large cadastral projects.
Following is a description of the steps the Souder-Miller Team uses in the performance of a GPS geodetic control survey:
Station Sketches - Our crews will prepare station sketches for all ground control points to aid in the recovery and identification of exact control. Sketches will include ties and distances to physical structures, station description as stamped on the cap/monument, direction of panel legs and vertical offset of monument to ground at panel.
GPS Data Acquisition Techniques - The Souder-Miller Team is well equipped for this assignment. This includes four Trimble GPS/RTK systems. The Team will follow the FGCS guidelines for GPS surveys. For static sessions, data is simultaneously collected for a minimum of 30 minutes at a sampling baud rate of 5 seconds. Only quasi-independent baselines will be computed and used to define the GPS network.
Antenna Height - At each setup the antenna height is observed once in meters and once in feet. The two measurements are reduced to one system of measurement and compared in the field before leaving the station. This approach eliminates the possibility of observing an incorrect instrument height.
Baseline Processing - All baseline vectors will be post-processed using Trimble Geomatic SurveyTM (TGO) software. Fixed bias, double-difference solutions will be determined for all selected baselines.
Loop Mis-closure Analysis - Loop mis-closures are computed on a daily basis. They are the first major quality control indicators. They are tabulated and compared with the FGCS guidelines. Each day, data will be processed and checked for accuracy by our GPS expert. Established techniques will be used to determine minimally constrained and constrained (usually constrained to the published NAD83 geodetic coordinates and NAVD88 elevations) network adjustments.
Final Coordinates - Final adjusted geodetic coordinates will be provided in NAD 83 (horizontal) and NAVD 88 (vertical) positions. Final coordinates can be provided in State Plane Coordinates, Geodetic Coordintes or Universal Tranvers Mercator (TM) as required by the client. Some agencies request State plane Cooridnates be presented in UTM as well. We can provide that coordinate transformation.
Final Survey Report – A report will be prepared containing information regarding the location and extent of the network, a narrative of the survey process, equipment used, tables summarizing the GPS and leveling loop mis-closures, results of the minimally constrained (free) adjustment, results of the constrained least squares adjustment, final State Plane Coordinates in U.S. feet, a network diagram and station sketches. For quality assurance purposes, the mis-closure table will also be included in the Final Report.