Monumentation Recommendations – IGS

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	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
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
	Rebar Reinforced Concrete	Bay Area Regional Deformation (BARD) Western Canada Deformation Array (WCDA) University NAVSTAR Consortium (UNAVCO)	Most commonly used monument type
	H-beam	New Mexico State Highway and Transportation Department	Excellent Stability
	Helical	United States Geological Survey (USGS)	Excellent Vertical and Horizontal Stability
Rod	Stainless Steel	WCDA	Long Term Stability Minimal effects from temporal solar radiant heating
	Metal Rod Brace	Southern California Integrated GPS Network (SCIGN) Basin and Range Geodetic Network (BARGEN) Pacific Northwest Geodetic Array (PANGA)
	Invar rod encased in concrete	UNAVCO	Good Stability Very low thermal expansion Low multipath signals
Mast	Rohn Tower	U.S. Coast Guard	Large heights can be used to reduce obstructions Concrete monuments used to anchor masts
	Stainless Steel	GPS Earth Observation Network of Japan (GEONET)
	Chain Link Fence Post	National Oceanic and Atmospheric Administration's (NOAA) Forecast Systems Laboratory (FSL)	Inadvisable for geodetic purposes, consider other monumentation choices
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
	Wall Mounted	Institute of Geophysics and Planetary Physics of the University of California, San Diego (IGPP-UCSD)

Other References:

Monumentation Design and Implementation Recommendations

Table 1: Considerations for Monumentation

Table 2: Types of monuments and examples of each

Other References:

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