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Monumentation Design and Implementation Recommendations

Table 1: Considerations for Monumentation

Desired Monument Characteristics	Parameters Affecting Monument	Characteristics of a Good Monumentation Site	Good Practice in Design of Monument
Stability with time Stable to a certain degree of accuracy Zero interaction with signal Low cost Simple design Ease of installation Corrosion resistance Long term survivability	Exposure to: Climate Impact Frost Action Shrinking and swelling of soil rock due to changes in moisture content Soil expansion and contraction Slope Instability Compression of Soils Presence of cavities due to karstic formations, such as found in dolomitic regions Erosion Diurnal and Seasonal Temperature variations Human Tampering Radio Frequency Interference Presence of faults Joints, fractures, and shear zones. Water Table Level Obstructions Presence of bedrock and its type and condition Vandalism	Shallow bedrock of high quality Clear horizon Safe from vandalism Clear of reflecting surfaces (fences, metal poles etc.) Not too far from receiver Ease of access Data accessibility via internet or phone line Continuous electric power No local crustal instabilities Controlled vegetation (growing horizon elevators)	Minimize multipath signals by choosing optimal above ground width and antenna height above ground level. Test the multipath environment and the radio frequency interference present at the chosen site before installation of monument. Minimize resonance cavities by minimizing empty space between top of monument and antenna. Minimize amount of metal in close proximity of antenna. Design monument to be higher than snowfall levels. Choose depth of monument anchor such that it is unaffected by frost action. Use materials with low coefficients of thermal expansion when high temperature variations are expected (Invar for example). Attach to solid bedrock for extremely stable foundation. Avoid mounting the GPS antenna within 24.4cm (9.6in), or exact multiples of this distance, of a potentially reflecting horizontal surface. Increase visibility of antenna above obstructions. Implement insulation when thermal expansion is a concern. Prepare lightning surge protection. Install vertical and horizontal stability measurement instruments (tiltmeters, inclinometers, strainmeters) when high accuracy (sub-mm level) is desired. Avoid nearby high voltage power lines.

Table 2: Types of monuments and examples of each

Monument Type	Description	Organizations	Characteristics	Links
Pier	C-Bar Reinforced Concrete	National Geodetic Society (NGS)	-Wide range of applications -Benign signal environment -High level of position stability -Inexpensive -Repeatability in antenna positioning -Long Term Survivability	National Continuously Operating Reference Station (National CORS) Site Monumentation Process Action Team 20 Final Report, U.S. National Geodetic Survey, December 20, 2000. Main report Installation Guidelines Additional Comments on NGS Design
	Rebar Reinforced Concrete	Bay Area Regional Deformation (BARD) Western Canada Deformation Array (WCDA) University NAVSTAR Consortium (UNAVCO)	-Most commonly used monument type	WCDA Concrete Pier Schematics UNAVCO Monument Installations
	H-beam	New Mexico State Highway and Transportation Department	-Excellent Stability
	Helical	United States Geological Survey (USGS)	-Excellent Vertical and Horizontal Stability	Description
Rod	Stainless Steel	WCDA	-Long Term Stability -Minimal effects from temporal solar radiant heating	Pedestal Overview Base Plate and Grout Design Installation Procedure
	Metal Rod Brace	Southern California Integrated GPS Network (SCIGN) Basin and Range Geodetic Network (BARGEN) Pacific Northwest Geodetic Array (PANGA)		Design and Installation of Deep Drill Braced Monument Installation of Shallow-Braced Monument Design and Installation of Short Drill Braced Monument PANGA Design and Installation of Braced Monument
	Invar rod encased in concrete	UNAVCO	-Good Stability -Very low thermal expansion -Low multipath signals	Red Butte, Utah GPS Station Schematic Greenland GPS Station Schematic Yellowstone GPS Stations Design
Mast	Rohn Tower	U.S. Coast Guard	-Large heights can be used to reduce obstructions -Concrete monuments used to anchor masts	Photos of the GPS Station Installation Considerations (pp. 84-91)
	Stainless Steel	GPS Earth Observation Network of Japan (GEONET)		GEONET Description Image of Stainless Steel Mast
	Chain Link Fence Post	National Oceanic and Atmospheric Administration's (NOAA) Forecast Systems Laboratory (FSL)	-Inadvisable for geodetic purposes, consider other monumentation choices	Description
Building	Rooftop	Texas Department of Transportation's (TXDOT) Regional Reference Points (RRP) SATLOC	-Inadvisable for geodetic purposes due to instabilities; consider other monumentation choices -If unavoidable, choose a load-bearing wall on a low-elevation building -Foundation of building must be stable -Larger buildings have more instability -Use vertical and horizontal stability measuring instruments to keep track of the movement of the building	Satloc Station at Orono, Maine
	Wall Mounted	Institute of Geophysics and Planetary Physics of the University of California, San Diego (IGPP-UCSD)		Schematic

Other References:

UNAVCO Monument Examples
Guidelines for Antarctic GPS monumentation
Leica Advanced CORS Systems: Guidelines to Site Selection for GPS Reference Stations
Panga GPS Site Information
Geodetic Site Monumentation, pp. 91-107
High Repeatability GPS Antenna-Mount Design
Global Positioning Systems for the Geosciences
Improved Stability of a Deeply Anchored Geodetic Monument for Deformation Monitoring

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