Leica Precision Circular Surveying Reflector Prism with Holder
GPR121
Model: GPR121
Specifications
| Prism Constant | Range | Centering Accuracy |
| 0mm | 3500m | 1.0mm |
Features
Removable Target Plate
Metal Holder
100% Original Leica brand Prism
Precision circular prism with anti-reflection coating, mounted in
metal holder.
Optical Survey Prism Applications
Surveying reflector prisms are used by surveyors and engineers to
measure the change in position of a target that is assumed to be
moving. Survey prisms are used for a wide range of monitoring
applications including:
· Rail Monitoring
· Settlement Monitoring
· Displacement Monitoring
· Deformation Monitoring
· Convergence Monitoring
Prism Range
Surveying Prisms, also known as retro-reflectors, redirect a
measuring beam back to the EDM (Electronic Distance Measurement)
for processing distance. There are two main factors for good range
measurement: prism diameter and beam deviation. If the beam
deviation is not accurate then the returned beam will miss the EDM
completely. This occurs mainly near the maximum range of the EDM.
Prism Holder Accuracy
Prism accuracy is determined by the physical location of the prism
in its canister and then to the prism holder.
Survey Prism Offsets
Some Surveying Prisms have an offset due to the fact that the
transmitted beam from the EDM takes longer to enter and exit the
prism. The longer time translates to a longer distance measured.
The distance is corrected by using an 'offset' and/or positioning
the prism in relationship to the plumb line of the prism holder.
Common offsets are 0, -17.5 mm, -30 mm, -34 mm, and -40 mm. The
offset is determined by multiplying the height of the prism against
the refractive index of the glass used.
