Scanning distance and over H2O

RABOR · Newbie Joined: Nov 29, 2006 Posts: 1

We have Lieca 3000 scanner which we used to scan the shoreline across a lake from a pier dock approx. 950' away. I know that this is pushing the limits for recieving any data at that distance, but we did get quit a few points and enough to do what the task required. When we went back the next day to continue we were unable to get any data. The weather conditions were very similar, and no settings were changed from the previous day. Does water effect the scanning process? Does lighting effect the reflectivity of an object? Any help/advise would be helpful.

thankx

enginyr · Newbie Joined: Jun 25, 2006 Posts: 5

What is the scanning being used for?

stuntmonkey

Count your self luck with the 950' range. And be careful scanning over water....you will get "phantom" returns which look like good data but is sometimes inverse.
You may want to try a Optec scanner for that type of range. I've scanned almost one half mile with data points 1/4" apart. Very good and light scanner.

Albert · Newbie Joined: Mar 22, 2007 Posts: 1

I believe there is a riegl scanner that can achieve that sort of range, the LPM-2K- scans up to 2.5km @ laser class 1m. You can check it out on

http://www.riegl.com/terrestrial_scanners/lpm-2k_/datasheet_lpm2k.pdf

Never used it though, but have used their 1km range scanner in similar conditions. They results were great!

FireFly · Newbie Joined: Sep 18, 2007 Posts: 1

Check out Optech's ILRIS-3D, but one with ER option. It will give great set of data over long distance. Check on www.optech.ca
I have used one in different applications and results are amazing.

3space · Posted: Wed Jun 04, 2008 2:16 am Post subject:

I've noticed a similar effect in land development surveys...

Stretching to that distance will reveal lots of "funny" things in scans... heat waves from a hot day, dust picked up by wind on a jobsite, etc... all can lead to errant data or no return... reflectivity depends on some factors, and they are different for different scanners.

All laser scanners emit light, so whether at day or night you should get a return within the measurement range, HOWEVER, different objects, coatings, textures, colors, etc return light differently. Like stealth fighters, they were designed to absorb or deflect the radar waves being emitted to them and therefore are invisible... so too can objects in your scan, like very dark surfaces or very shiny glassy surfaces, like water.

I imagine what happened to you was the temperature change or the time of day or loca temperature of the scanner, even slightly may have changed your scan range and since you were already pushing it for distance, it didn't take much to not get the same results as the day before... but that's just a blind guess.

Sorry for the novel, hope this helps.
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