Extracting x,y,elev subsets without ESRI ARC software?

By Tim Loesch Date 2012-12-11 15:58

I would use LASTOOL - LAS2TXT to do this. While LASTOOLS is not free - parts of it are free and LAS2TXT is one of them. Using LAS2TXT you can export to x,y,z format easy enough.

Check out the tip sheet - LAS tile processing using LASTOOLS at - ftp://ftp.lmic.state.mn.us/pub/data/elevation/lidar/tools/lastools/LAS_File_Processing_Using_LASTOOLS.pdf

I built this tipsheet to help folks through a variety of scenarios using LiDAR data. You'll be interested in the topic on page 7.

hope that helps.

tim

By chuck Date 2012-12-14 17:05

I used your pdf file for instructions...and activated LAS2TXT. It requires that the LIDAR data be a *.LAS type file. However, when I downloaded the Stearns Cty LIDAR zipped file (25GB)...about 100 files were unzipped. None are listed as *.LAS. The largest file is: a0000003b.gdbtable (13.34GB). All of the files are suffixed 'gdb***'. I know that ESRI-ARC software can handle 'gdb' files. But as noted...I don't own ESRI software. I need additional advice on how to proceed from a 'dgb' file format to '*.LAS'. Thanks

By LesEverett Date 2012-12-14 23:35

One of the real experts can jump in here, but meanwhile it looks like you've downloaded the zipped geodatabases that include the LiDAR data products (DEM, Contours, etc.) instead of the point data. The point data are found as compressed LAS files, called LAZ files in their compressed state. There is a folder labeled LAZ containing the compressed LAS (LAZ) tiles. Text in the Readme files says: "WORKING WITH MINNESOTA LAS/LAZ DATA: When you download data from the Minnesota LiDAR ftp site (ftp.lidar.dnr.state.mn.us) the original LAS file has been compressed to LAZ format using LASTOOLS | LASZIP. If you are using LASTOOLS, you don’t need to unzip them because LASTOOLS will operate on compressed files. But if your intent is to use the LAS files in some other software that cannot read LAZ compressed files you’ll need to uncompress them. To do this use the LASZIP tool." It goes on to describe how to do that. You can find that document as well as the LAS tools folder at ftp://ftp.lmic.state.mn.us/pub/data/elevation/lidar/
Note the special readme file for Stearns County in the Stearns County folder.

By Tim Loesch Date 2012-12-18 18:16

Les is correct - you'll need to download the compressed LAZ file from the county/stearns/laz folder.

Note that if you are using LASTOOLS - LAS2TXT you don't need to uncompress the LAZ file, LAS2TXT will work directly on the LAZ file saving you some time.

Also note that the LAZ files for Stearns county contain only Bare Earth points - that's all we got from the county.

tim