4.25.2005

Processing the LIDAR

I just finished processing the City of Sacramento LIDAR data to generate a 2' DEM. It took 12 straight days of processing (24/7). I am currently working on a QA/QC of the DEM mosaic.

Thanks to the UC Berkley guys for providing me batch routines for some of the initial processing.

I used several software packages to generate the DEM partly because of the amount of data I had to process and the fact that I did not have any developed batch routines that would work within ESRI.

PERL - for processing ascii text points to new overlapping tiles
Surfer - to Grid the point data using a Kriging algorithm
Python - to batch import Surfer text to ESRI text format and ESRI Grid format
ESRI - to generate the DEM mosic and QA/QC

The LIDAR data came from a flight done by Merrick in 2004. The data were in over 1300 text files containing the XYZ location of each laser point. Since the files were not overlapping, I used the PERL script to re-bin the ascii text points to new files (1370 files to 70 files). I next used Surfer and a Surfer Script to create the overlapping Surfer Grids. I then used a Surfer script to generate ASCII text formatted files. From here I ran a command line script to convert the Sufer text to ESRI text. I then ran a Python script I created to batch process the Ascii text files to ESRI Grid image files. The "glob" code helped me do this. Finally, I created a DEM mosaic using the Mosaic to New File function within ArcGIS.

Check the links for more info on what LIDAR is.
NC

3 comments:

Anonymous said...

Hi. I am an ArcGIS novice, and I need to convert a whole bunch of ARC ASCII files to GRIDs. Would you be willing to send me your python script that does this? Thanks for your time.

Jason Smith
jsmith@cortex.ca

Scott Lawrence sdlpci@cis.rit.edu said...

Hi there. This post came up on a googling for "LIDAR .xyz". Can you point me at some docs on the net that describe the file format? I've got only a vague understanding of it, and I have some data here I want to manipulate and experiment with, but I'm not familair with the format.

Sadie said...

Another hopeful looking for a nice batch processing script - I'm trying to do a similar ascii-raster conversion blitz.

cheers,

Sadie Ryan
sjryan@stanford.edu