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GeoMax ZRP1 360° Prism

Image of GeoMax ZRP1


The GeoMax ZPR1 360° Prism is a rugged passive 360° reflector designed for Total Stations. Consisting of six corner-cube prisms joined together, this device will reflect any EDM beam directly back to its source, regardless of how or where it is positioned.

While the GeoMax ZPR1 360° surveying prism has an overall accuracy of 5mm, this improves to 2mm when you point directly at any of the three prisms that are marked by yellow arrows. Its range is effective up to 600m and has a standard offset of 23.1 mm.

The rubber padding on the top and bottom to protect the device against falls when mounted on a prism pole.

The ZRP1 is a direct equivalent to Leica’s GRZ4 surveying prism.


Height Offset:86.0 mm
Absolute constant: -11.30 mm
Leica constant: +23.10 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.


Below is a list of frequently asked questions about GeoMax ZRP1.

What is the prism constant for the GeoMax ZRP1?

The absolute prism constant (true value) for the GeoMax ZRP1 is -11.3mm. The prism constant as defined for Leica instruments for GeoMax ZRP1 is 23.1mm. For a more detailed explanation on prism constants please see this article.

Can I use the GeoMax ZRP1 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 ZRP1 with a Leica instrument you should use 23.1mm as the prism constant value.

What is the height offset of the GeoMax ZRP1?

The GeoMax ZRP1 height offset is 86.0mm. This is measured from the mounting point to the centre of the prism.