Topography - Terrestrial Laser Scanner Trimble GX

Parameter to be measured:

• surface topography
• snow cover

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

Price:

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

Links

Projects that used the above equipment:

• SESAM II

Other related web sites:

References