Date: Subject: HISTORY OF THE CITY OF OKLAHOMA CITY’S PRIMARY CONTROL NETWORK The City of Oklahoma City’s Primary Control Network was established in 1990 and was based the National Geodetic Survey (NGS) datum, NAD83 (1986) adjustment. The contractor, Atlantic Aerial Surveys, Ltd. set some 450 control monuments and aerial targets across town. The Network was reported as Second Order, Class II horizontally and Third Order vertically at the time of conception. Our survey crews have used and tested the Network control extensively over the last 12 years or so and as a general rule, the Network reported positions check well within the Network itself. To date, there are approximately 197 Primary Control points remaining across town. September of 2005 The Survey Section began running two-hour static GPS sessions on the Primary Control Network using our Trimble 4000ssi units. We processed the raw static sessions through NGS’ Online Positional User’s Service (OPUS), which constrains the results to NGS’ modern datum, NAD83 (CORS96). The results we found were pretty much in line with NGS’ reported “superseded values”, horizontally. The typical discrepancy in coordinates was; Northing- 0.3’ and Easting –1.2’ on the west edge of town and Northing –0.6’ and Easting –1.6’ on the east edge of town. The vertical discrepancies were left unexplained and were typically in the –0.1’ to the –1.0’ range, (the CORS96 elevations being the lower of the two) as the CORS96 adjustment did not provide changes in elevations. Although I researched high and low, I could not find the specifications or parameters, which Atlantic Aerial used to adjust the Network at the time. I can only surmise that they adjusted the Network to a local plane representing the greater OKC area, maybe with the Geod model of the time. February of 2006 MEMORANDUM The City of OKLAHOMA CITY Field Services Division

CORS96 ADJUSTMENT REPORT

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Date:

Subject:

HISTORY OF THE CITY OF OKLAHOMA CITY’S PRIMARY CONTROL NETWORK

The City of Oklahoma City’s Primary Control Network was established in 1990 and was based the National Geodetic Survey (NGS) datum, NAD83 (1986) adjustment. The contractor, Atlantic Aerial Surveys, Ltd. set some 450 control monuments and aerial targets across town. The Network was reported as Second Order, Class II horizontally and Third Order vertically at the time of conception.

Our survey crews have used and tested the Network control extensively over the last 12 years or so and as a general rule, the Network reported positions check well within the Network itself.

To date, there are approximately 197 Primary Control points remaining across town.

September of 2005

The Survey Section began running two-hour static GPS sessions on the Primary Control Network using our Trimble 4000ssi units. We processed the raw static sessions through NGS’ Online Positional User’s Service (OPUS), which constrains the results to NGS’ modern datum, NAD83 (CORS96). The results we found were pretty much in line with NGS’ reported “superseded values”, horizontally. The typical discrepancy in coordinates was;Northing- 0.3’ and Easting –1.2’ on the west edge of town and Northing –0.6’ and Easting –1.6’ on the east edge of town.

The vertical discrepancies were left unexplained and were typically in the –0.1’ to the –1.0’ range, (the CORS96 elevations being the lower of the two) as the CORS96 adjustment did not provide changes in elevations. Although I researched high and low, I could not find the specifications or parameters, which Atlantic Aerial used to adjust the Network at the time. I can only surmise that they adjusted the Network to a local plane representing the greater OKC area, maybe with the Geod model of the time.

February of 2006

The Okc Survey Section completed running more than 400 each, minimum 2 hour static sessions on the 197 Primary Survey Control Monuments in the Okc Metro area. A minimum of 2 each, 2 hour static sessions were run on each Primary Survey Control point. The results were weighted and averaged, some highs and lows discarded and the results are reported.

September 2008

The City of Okc purchased 2 new Trimble R8 rovers that are operating on the WDS RTK Network in the metro area. This allowed us to further test the Primary Control. Another 600 plus RTK sessions were included in the weighted positions.

MEMORANDUMThe City of

OKLAHOMA CITYField Services Division