CORS Orthometric Heights

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CORS Concrete Pillar Antenna Mount
Field Procedures to EstablishCORS Orthometric
Heights
Curt Smith Denis Riordan
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NDGPS
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http//www.scign.org/
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1. Direct Level Tie from Adjacent Bench Mark to Top
   of Mounting Surface Sighting Surface

Backsight
Foresight
BM
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1. Direct Level Tie from Adjacent Bench Mark to Top
   of Mounting Surface Using Invar Strip

Invar Strip
Backsight
Foresight
BM
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1. Direct Level Tie from Adjacent Bench Mark to
Top of Mounting Surface

• Pros
• Established BF digital level routine
• Most accurate transfer of elevation
• Will achieve Second Order, Class 1 or 2
• Cons
• Cant directly observe to desired surface
• Antenna in place move antenna during
  measurements
• Digital levels optical system needs to be
  calibrated
• Invar strip - plumb and on desired surface

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2a. Direct Level Tie from Adjacent Bench Mark to
Reference Mark on Monument
Foresight
Backsight
BM
RM
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2b. Equipment (?) Measure-up from Reference Mark
on Monument to Antenna Mounting Surface
Constant
RM
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2. Equipment (?) Measure-up from Reference Mark
on Monument to Antenna Mounting Surface

• Pros
• Accurate transfer of elevation to reference mark
• Permanent reference mark on monument
• Cons
• Currently no established procedures
• Cant directly observe to desired surface
• Antenna in Place must be moved during
  measurements
• Conventional Elevation only to reference mark
• Unknown accurate distance measuring equipment
• Equipment and accuracy concerns for measure-up

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3a 4a. Direct Level Tie from Adjacent Bench
Mark to Reference Mark at Building
Backsight
Foresight
BM
RM
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3b 4b. Equipment (?) Measure-up from Reference
Mark at Base of Building to Reference Mark on Top
of Building
Constant
RM
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3c. Direct Level Tie from Adjacent Reference Mark
to Top of Antenna Mounting Surface
RM
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4c. Direct Level Tie from Adjacent Reference Mark
to Reference Mark at Bottom of Antenna Support
Structure
Foresight
Backsight
RM
RM
RM
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4d. Equipment (?) Measure-up from Adjacent
Reference Mark to Antenna Mounting Surface
Constant
RM
RM
RM
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5. Trigonometric Leveling from Bench Mark to
Antenna Mounting Surface
Backsight
Foresight
BM
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5. Trigonometric Leveling from Bench Mark to
Antenna Mounting Surface

• Pros
• Automatic vertical angles by robotic total
  stations
• Draft procedures from Audie Murray and Charlie
  Glover
• Cons
• Cant directly observe to desired surface
• Antenna in place move antenna during
  measurements
• Distance limitations (?)
• Mix of data conventional/trigonometric leveling
• Procedures to get data into NGS Database?

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6a. Trigonometric Leveling from Bench Mark to
Antenna Mounting Surface
Foresight
Backsight
BM
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7a. Trigonometric Leveling from Bench Mark to
Reference Mark on Top of Structure
RM
Foresight
Backsight
BM
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7b. Trigonometric Leveling from Reference Mark
to Antenna Mounting Surface
Backsight
Foresight
RM
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8. Ellipsoid Height Differences Referenced to
Bench Marks via GPS Observations
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8. Ellipsoid Height Differences Referenced to
Bench Marks via GPS Observations

• Pros
• Draft procedures from NGS Field Operations
• Antenna in place use during measurements
• Provides GPS/BM in area for geoid modeling
• Cons
• Accuracy limitations
• Will not produce Second Order, Class II
  elevations
• Requires bench marks within proximity of CORS
• Distance limitations (?)

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The FGCS Specifications shall apply unless
specifically superseded by the requirements
specified below. If there is a conflict
between the FGCS Specifications and this document
for a given specification or procedure, this
document shall take priority.
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Further Study and Development

• Point Identifiers for ARP when establishing Ortho
• Distance to surrounding bench marks
• Optional devices for measure-ups
• Guidelines and specifications for each option
• Combining multiple measurement systems data