| |
EDM instruments are available to measure
distance using light and radio waves, and have been used in Australia
since very soon after their invention. The distance is calculated either
from the time difference between a transmitted pulse and a return pulse
or the phase difference between a transmitted and a reflected beam of
radiation.
|
EDM and
Electronic Theodolite
|
EDM are an intergral part of Total
Stations and this is the usual mode of operation. However there
are "stand-alone" EDM units, which when used together
with an electronic theodolite, function as a total station.
|
Total Station |
Electromagnetic distance measuring equipment use three different wavelength
bands:
- Microwave systems:
- Range up to 150 km
- Wavelength 3 cm
- Not limited to line of sight
- Unaffected by visibility
- Light wave systems:
- range up to 5 km (for small machines)
- visible light, lasers
- distance reduced by visibility
- Infra red systems:
- range up to 3 km
- limited to line of sight
- limited by rain, fog, other airborne
particles
|
|
The links below provide more information on
the operation and calibration of EDM.
|
