Recognizing the ever increasing use of Global Positioning Systems (GPS) as a
means to establish the position of United States Public Land Survey corners,
property boundaries, and geographic information data, the Warrick County
Surveyor, James E. Niemeyer, contracted with BLA to densify a horizontal
control network within Warrick County on which state plane positions were to
be established. Working with Mr. Niemeyer, the position of sixteen (16)
proposed monuments were identified at an approximate twelve (12) mile
spacing. In addition to the spacing, the criteria used to establish the
monument locations included 1) suitability for GPS observations, 2) easily
accessible and 3) low potential for disturbance in the foreseeable future.
Locations were established within county owned property or existing public
rightof- way, where possible. However, several of the monuments ended up
being located in privately owned cemeteries or church properties. In those
instances, a written agreement was obtained from the land owners to place
the monument at a certain location on the property and to allow future
access by land surveyors so they can occupy the monument with surveying
equipment. The monuments that were constructed consisted of up to four
sections of three foot aluminum rods driven to approximately three inches
below ground level. A spherical datum point with a drilled dimple which ma
ks the exact monument position was
attached to the top aluminum rod section. In order to eliminate any frost
heave action on the rod, the top 24 inches were placed in a PVC sleeve filled
with grease. A short section of 6" diameter PVC pipe was placed vertically
around the actual monument and an access cover was placed inside it to protect
the driven rod. The access covers were stamped to identify it as a "Warrick
County Surveyor Control Monument" and to identify the monument number.
Information and references to assist locating the monuments is included in
this report. The monument positions were established using Static GPS Methods.
A combination of Trimble and Leica Dual Frequency GPS receivers were utilized.
A total of eight units, four base stations and four rovers were used
throughout the data collection phase. Two observations of at least 45 minutes
each were made at each monument while base stations were simultaneously
positioned and collecting GPS data at four separate NGS Order "B" HARN
stations in Warrick County and the adjacent counties. Information on the HARN
stations utilized has been included as part of this report. A partially
constrained least squared adjustment of the collected GPS data was performed
fixing the published positions of the four NGS HARN stations that were
occupied. The least squares adjustment was performed utilizing "StarNet-Pro"
least squares adjustment software by Starplus Software Inc. The positions of
the fixed HARN stations that were used were based on the NGS National
Readjustment NAD 83 (NSRS 2007). Utilizing the readjusted HARN positions,
geographic as well as Indiana State Plane, West Zone NAD 83 (NSRS 2007), US
survey feet coordinate positions were established for the sixteen monuments
constructed as part of this project.
Below are Control
Points that
are located in the Warrick County Surveyor's Office,
they have been scanned, and
converted to PDF files,
Adobe Reader
is required to view.
