Henrico County Geodetic Control Network Maintenance

Project Summary

Timmons Group was contracted by Henrico County, Virginia to provide maintenance to their existing geodetic control network. Timmons Group originally established this network in 1998.  The scope of work included visiting each concrete monument and its associated azimuth mark, determine its health, re-set any missing monuments, perform GPS observations on any new monuments or any monuments that appeared to be disturbed, take new digital photographs if needed and update all recovery sheets.  A least squares adjustment was performed on all new GPS observations using the existing geodetic network as fixed control.  The resulting positions for new or re-observed monumentation fell within First Order accuracy standards horizontally and Second Order, Class II vertically. Five Trimble dual frequency geodetic receivers were utilized to collect the GPS data and Trimble Geomatics Office software was used for post-processing and adjustments.  A web-based recovery document was produced for all of the control monuments within the County and was integrated directly into the County’s existing GIS.  This information is currently available on-line for the 348 control monuments within the County.  The address is http://ns1.co.henrico.va.us/devsite/monumentation/.