1. 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found were pretty much in line with NGS’ reported “superseded values”, horizontally.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.
MEMORANDUM
The City of
OKLAHOMA CITY
Field Services Division