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Discussion: Munching LIDAR best practices

in: Orienteering; General

Feb 4, 2018 12:40 AM # 
Backstreet Boy:
Sometimes I have success with Karttapullautin but many data sets I download I can't get it to finish on - either a format issue or out of memory.

I recently updated to the latest version and still have the same problem.

Got a Windows 8.1 laptop with 4GB of RAM. Is there a limit to how much RAM the program can address, is it 4GB?

The latest version of OCAD is supposed to import LIDAR, can it handle data sets Karttapullautin can't?
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Feb 4, 2018 1:08 AM # 
cedarcreek:
I use task manager to judge how much CPU and memory KP (and other lidar apps) are taking. I can run three KP processes typically, but I don't dare use a browser. With 1 or 2 KP processes, I can browse as long as I don't open too many tabs. I can't run QGIS at the same time I'm processing with KP or OL-Laser.

In my experience, KP can handle quite large files, but I typically tile big datasets to smaller files because it seems to run faster, and the merge function in KP is excellent and doesn't have artifacts at tile edges.

The biggest issue I've had with KP is giving it data in feet. That somehow causes the solution to take much more memory than expected. There may have been changes in KP that now let it not blow up when it's given feet. KP has been updated many times since I found the feet problem.

I suggest opening task manager (assuming windows), and looking at processes sorted by CPU % and Memory. (Memory is probably the problem, but CPU % can indicate how many parallel processes you can run.)

Finally, I recently noticed that QGIS didn't seem to show up in task manager. It might be hidden by processes with other names, but I recall my computer was basically frozen and the task manager showed numbers that didn't jibe with reality.
Feb 4, 2018 1:08 AM # 
rm:
Split the dataset into tiles using Lastools. Then run Kartapullautin on the set of tiles. It's supposed to even merge the resulting map tiles.

Data reduction is also a possibility (reduce the number of data points per square meter, using I think Lastools also(?)).

I find that it runs out of memory on the cliff stage (if it does), so adjusting the parameters for cliff detection might also affect this issue, but I'm not sure.
Feb 4, 2018 1:49 AM # 
haywoodkb:
Be sure all your data is in WGS-84 and meters. Read the metadata. Any mention of "feet" or "state plane" coordinates is bad news. Convert all your data to WGS-84, UTM, and meters before you begin.
Feb 4, 2018 3:19 PM # 
hughmac⁴:
Lots of good answers above about KP data best practices: make sure it's WGS-84/UTM meters, feed smaller bites to KP batch mode, reduce the density of the data (I like 20%!!) ... LASTools for all of that.

I don't believe OCAD can 'handle' LiDAR in any wider way than KP, but haven't experimented too deeply, as I still much prefer the contours generated by KP.

Windows 8.1 is terrible. Do a fresh wipe / install of Windows 10. Free for you! https://www.microsoft.com/en-us/software-download/... (not the Update, but the Installation Media method)
Feb 6, 2018 5:50 AM # 
TheInvisibleLog:
But run the risk of losing listenable audio after the upgrade.

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