What is an Optical Survey Prism?

What is an Optical Survey Prism?

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. Prisms reduce the scatter of the beam as it is reflected back to the total which allows for both a more accurate measurement and a longer range that the measurement can be made.

Optical Survey Prism Applications

Survey 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

Optical Survey Prism Installation

Monitoring prisms should be installed using the following guidelines:

  • Attached to a rigid structure that is sufficiently stiff as to not move through a single monitoring cycle
  • Located to minimize the effects of temperature and radiant heat on a target
  • Installed with clear sight lines back to the total station
  • Avoid sight lines that require shooting through a fence or another mesh
  • Avoid sight lines shooting just past corners which can cause refraction
  • Avoid sight lines that include a source of heat that can cause a heat shimmer

Types optical survey prisms

  • Mini prisms are cheap and reliable, and are a good multi purpose prism for short to mid range measurements.
  • 360 prisms are simple to use for sharing prisms in a multi station network and all angles have a shared center.
  • Dual prisms are reliable shared prisms with shared centers. They are less expensive than 360 prisms, but have to be aimed at each total station in a network.
  • Full size reference survey prisms are ideal for high range precision monitoring and can be used to calibrate a monitoring network

Specto Technology provides a wide range of total station survey prisms for every application. Our premium quality prisms have been rigorously tested and are trusted by our customers to provide reliable and accurate measurements on large construction projects across the US. The Optical Survey Prisms we provide can be used with any brand of total station including Topcon, Sokkia, Leica Geosystems, Trimble Geospatial, Nikon, GeoMax and NorthWest.

Please see the brochure  and the table below for a comparison of our prisms, all of which are available to purchase online, with same day and free shipping available. We help our customers avoid project delays by keeping a large inventory of prisms in stock, and have selected the highest quality manufacturers to minimize issues with defective prisms.

L-Bar Prism Lightweight Prism Rail Clip Prism Road Prism Reference Prism
Price $55 $55 $135 $85 $225
Accuracy ≤ 5″ ≤ 5″ ≤ 5″ ≤ 5″ 2″
Maximum Range 1000m 1000m 1000m 1000m 3500m
Reflectivity 95% 95% 95% 95% >95%
Prism Diameter 25.4mm 25.4mm 25.4mm 17.8mm 62mm
Best Material for Securing Anchor Bolts Adhesive Epoxy or Anchor Bolts Adjustable clip (included) Adhesive Epoxy & Anchor Bolts Anchor Bolts
Application Standard Optical Survey Monitoring Best to be used on surfaces that are not to be penetrated Railroad Track Monitoring Roadway Monitoring Reference Backsights, Long Distance Monitoring, Moving Targets