| Description |
GPS (POINT COVERAGE OF 91 & 97 GPS POINTS):
1991 GPS Monuments:
Delaware County has established two sets of GPS monuments in 1991 and 1997.
The first set included 110 points (55 pairs) of first order coordinates and was established by Woolpert. These points were used to create the first Orthophoto base (conventional Orthophoto) for the cadastral database and did not include elevation data. The X-Y coordinates of all these points are included in a text, a DXF, and an Arc/Info export file on the CD. The 1991 monuments are published in Ohio State Plane Coordinate System, North zone, and the horizontal datum is NAD 83 (86 Revision).
1997 GPS Monuments:
In 1997, Canter Surveying/GPS Services, Athens, Ohio was contracted by the Delaware County Auditor’s office, to provide surveying services in Delaware County, Ohio. The purposes of this survey were:
-to support aerial photogrammetric operations
-to densify existing permanent control monumentation.
GPS observations were completed using geodetic-grade dual frequency receivers. Positional accuracies expected are 0.010m + 1ppm between any two points horizontally and 0.020m + 1ppm vertically. Two-hundred and twenty-eight (228) NGS Class-C monuments (poured in place concrete with brass tablet) were set and positioned during this project. Reference diagrams for each monument were prepared in hard copy and digital format for inclusion in the DALIS (Delaware Appraisal Land Information System) database.
The 1997 monuments are published in Ohio State Plane Coordinate System, North zone, and the horizontal datum is NAD 83 (86 Revision). The vertical datum is North American Vertical Datum (NAVD) 88.
In 2003, the Delaware County Engineer inspected all of the GPS monuments. This survey revealed that 35 of the original GPS monumnets had been destroyed due to construction, or other activities. This "status" is recorded in the Status field as True for an existing monument or False for a destroyed one.
NOTE: Monument 97-116 contains an error. The z value for this monument should be 913.1 feet. Any data downloaded prior to April 2008 should be updated. An updated version of the data can be downloaded here.
For questions regarding 1997 GPS Monuments contact:
Canter Surveying Robert C. Canter, P.S.
227 Columbus Road
Athens, OH 45701
(740) 592-5706