Control Points

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 maks 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.