Surveying Circular Prism Reflector GPR121 1mm Centering Accuracy
Leica Prism
Model: GPR121
Surveying 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
GPR121 Prism Features
1. Removable Target Plate
2. Metal Holder
3. 100% Original Leica brand Prism
4. Precision circular prism with anti-reflection coating, mounted
in metal holder.
Main Data
| Prism Constant | Range | Centering Accuracy |
| 0mm | 3500m | 1.0mm |
What is an optical survey prism?
Optical Survey Prisms are a specially designed retro reflector,
specifically a corner reflector, that is used to reflect the
Electronic Distance Measurement (EDM) beam from a total station.
A survey prism reflects the EDM beam back to its source with both a
wide angle of incidence and with high precision
What is 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.
What is Prism Holder Accuracy?
The range of a prism results from, among other things, its coating
and the glass geometry. Measurement errors occur frequently at
close ranges when prisms without anti-reflex coating are used, as
the front of a prism always directly reflects a certain percentage
of a signal. Errors occur in the use of prisms without copper
coating on the back side when moisture droplets accumulate or the
prism becomes foggy.
High standard quality prisms have a special coating on the
reflective surfaces – the Anti-Reflex Coating, and a copper coating
on the reverse side. Without these, the range of distance
measuring, ATR and Powersearch would be reduced by up to 30%. The
workmanship and the durability of the copper coating are decisive
for a long life.
The glass dimensions, the position in the holder and with it the
areal orientation, are important for measuring accuracy.
What is 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.
Transparent choice
Leica Geosystems offers a transparent selection of prisms in
various sizes for different areas of application. These are
standard prisms, special prisms, mini prisms as well as monitoring
prisms.
Professional 5000: HIGHEST ACCURACY
Professional 3000: MAXIMUM LIFETIME
Professional 1000: COST EFFECTIVE MEASURING
