Topography - Terrestrial Laser Scanner Trimble GX

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Contents

Parameter to be measured:

  • surface topography
  • snow cover

Trimble gx.jpg

Method:

  • terrestrial laser scan

Equipment:

  • Laser Scanner
  • battery kit
  • reflector targets
  • software PointScape, PocketScape

optional: handheld operation unit (TSC2), Wireless kit

  • Laptop, tripod, additional reflectors (not included)

Advantages:

  • nominal currently (2009) one of the most precise TLS on the market (angular and distance resolution, laser footprint)
  • green laser works better on snow and moist surfaces than IR lasers
  • both operation software options PointScape (Windows) and PocketScape (Windows Mobile) are intuitive and well designed
  • PointScape enables scanning selected polygons (opposed to rectangular selections, saves time)
  • support of target spheres (beside flat targets)
  • SureScan option: automatic adjustment of angular resolution during scanning to achieve homogeneous spatial resolution
  • carrying backpack enables cross-country transport (not including tripod, batteries and targets)

Disadvantages:

  • bulky and heavy: transport in the original box as ordinary flight baggage not possible; carrying in the field is painful
  • limited scan distance: typical distance in the field is less than 250 m
  • limited scan speed: typical speed < 500 points/s
  • poor camera with heavy distortion in live view; bright scenes (snow under sun) can appear completely blinded
  • painful selection of scan polygon when spanning more than the current angle of view
  • polygon scan area selection not available in PocketScape
  • high power consumption: standard battery pack usually lasts 2 - 3 hours, occasional shutdown on low battery without warning observed
  • start-up time of ~ 3 min
  • runs on 24 Volts - car battery adapter is included, but needs two batteries
  • no tilt-mount available; for looking up-/downward, though setting up scanner inclinated on tripod is possible within limits

What to watch out for:

  • Laser is not eye safe, take care
  • fit of target spheres can be very poor (without warning); verify or repeat in alternative software
  • reflective targets seem to be "overexposed" (at least at shorter distances) and cannot be used
  • laser beam can partially penetrate PE target spheres
  • minimum range ~ 2 m
  • cables attached to moving part of scanner - danger of "strangling" during rotation
  • check if you really need the handheld operation unit TSC2: operability is usually better on a larger screen of a real laptop

Problems/Questions:

Price:

with Wifi-kit ~ 120000 € (2009, Germany)

Links

Projects that used the above equipment:


Other related web sites:

References

TribleGX Panorama.jpg

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