Alan Brubaker, P.E., P.S., County of Summit Engineer
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This program is designed to provide quick and easy retrieval of geodetic control data in Summit County. The data are from several sources and it is important that the user understand the data before using them.
Summit County began to gather data for a Geographic Information System in 1994. At the time the latest horizontal datum was the North American Datum of 1983 (1986 adjustment) or NAD83 (1986). Since then the National Geodetic Survey (NGS) has installed a High Accuracy Reference Network (HARN) and now publishes data in NAD83(1995 adjustment).
Since the coordinates all of Summit County’s GIS data are in the 1986 adjustment the coordinates published here are from that adjustment. For HARN coordinates on NGS points visit the NGS web site at www.ngs.noaa.gov.
As previously stated, these data are from several sources. The first source is NGS. We have taken the last version of their dsdata text file prior to the HARN adjustment and made it the core that we built around. The NGS uses a point identification string (PID) to identify control points. The PID consists of two alpha and four numeric characters (ex.: KY1461). The NGS points in this database have PID’s that begin with KY or MB.
Another source is the control installed to support the aerial photography for the Summit County GIS. These points were observed and adjusted by Woolpert using Global Positioning System receivers. Both horizontal and vertical coordinates were obtained. The horizontal are first order and the vertical third order. The PID’s for these points begin with GS.
A third source is the County Engineer. Some of these points were observed by County Engineer crews using GPS equipment at the same time that Woolpert was observing the GIS points. These points were included in the adjustment of the GIS points. Some of the points have adjusted second order elevations run by County Engineer crews. Some of the points are old USGS benchmarks. Like the NGS database points that are vertical control only have scaled locations. All of these points have PID’s beginning with CE.
Included in the CE points are some points from the Cleveland Regional Geodetic Survey. These have published coordinates in the CRGS coordinate system with converted figures for geographic and State Plane Coordinates. Little information is available regarding how these monuments were set and how to convert between datums. We have therefore used scaled coordinates to locate these and have listed no horizontal order. We have listed the vertical order as third and believe these monuments will only be useful to Summit County surveyors as third order vertical control.
Also included in the CE points are some points that locate some existing centerline monument box assemblies in the Townships of Copley and Bath. This was an experimental project to provide grid coordinate values in a developed area to be used in conventional surveying. The County Engineer provided personnel to perform the GPS field work. Campbell and Associates, Inc. provided the GPS equipment, planning and post processing to develop the coordinate values.
Finally we have some points set by private companies and individual. These have a PR prefix on the PID.
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