Monumentation Recommendations

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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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