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GeoMax GRZ122 360° Prism

Image of GeoMax ZRP122


The Geomax GRZ122 360° Prism is a lightweight passive reflector for use with Robotic Total Stations. It consists of six corner-cube prisms that are joined together and are arranged in a way that EDM signal reflects directly back to its source, regardless of the position. This will save you time and effort as you no longer need to adjust the prism when you move your Total Station.

The GRZ122 surveying prism can withstand the rigors of the field, being protected by rubber mountings on the top and bottom.

This reflector has an overall 3D pointing accuracy of 2mm, a working range of 600m, and a prism constant of 23.1mm. Additionally, the GRZ122 Surveying Prism includes a built-in point that allows it to be positioned directly on a survey mark at a height of 78mm and a 5/8″ thread adapter for mounting a GNSS antenna on top, allowing for integrated surveying.

A direct equivalent to the GRZ122 is the Leica GRZ122 360° Pro Surveying Prism.


Height Offset:86.0 mm
Absolute constant: -11.30 mm
Leica constant: +23.10 mm
Centring accuracy:±2.0 mm
Mount:12mm (Leica) Spigot


Below is a table with approximate prism ranges, based on atmospheric conditions.

Surveying Prism PoorGoodBest
ZPR100 Standard Prism 1800m3000m3700m
3x ZPR100 Prisms2300m4500m5400m
ZRP1 & GRZ122 360° Prisms800m1500m2100m
Leica GRZ101 360° Mini Prisms500m800m1000m
ZMP100 & ZMP101 Mini Prisms800m1200m2100m
ZTM100 Reflective Tape200m200m200m

Atmospheric conditions are defined as:

  • Poor – Strong haze & 5km visibility or strong sunlight with severe heat shimmer
  • Good – Light haze & visibility about 20 km or moderate sunlight with slight heat shimmer
  • Best – Overcast, no haze, visibility about 40 km & no heat shimmer.

GeoMax ZRP122 FAQ

Below is a list of frequently asked questions about GeoMax ZRP122.

What is the prism constant for the GeoMax ZRP122?

The absolute prism constant (true value) for the GeoMax ZRP122 is -11.3mm. The prism constant as defined for Leica instruments for GeoMax ZRP122 is 23.1mm. For a more detailed explanation on prism constants please see this article.

Can I use the GeoMax ZRP122 with a Leica instrument?

Yes, you can use the prism with a Leica instrument as long as you set up the correct prism constant in the instrument settings.

What is the prism constant value that I need to use with a Leica instrument?

In order to use the GeoMax ZRP122 with a Leica instrument you should use 23.1mm as the prism constant value.

What is the height offset of the GeoMax ZRP122?

The GeoMax ZRP122 height offset is 86.0mm. This is measured from the mounting point to the centre of the prism.