PCAP to LAS

[JFayne]

Hello LAStools group!

I recently began working with 3D points captured in a .pcap data format from a Velodyne terrestrial scanner. This data was collect from the Computer Science department of George Mason University for a 3D campus mapping project. Because I usually work with aerial LiDAR in the las or laz formats, and the CS students required pcap for their project, the pcap format is a little bit of a challenge for me.

Using VeloView, I was able to extract the points into several hundred (if not thousand) csv/txt files, one for each scene, where scenes are separated by time and I imagine, pulse sets of some sort. For each of the csv files, I can create a 3D point shapefile in QGIS or ArcMap. Still, this isn't what I am looking for. The data acquired around campus used a scanner mounted to  to a golf cart, and features roads, buildings, trees, etc. I am trying to identify building and tree features (to extract) to get a digital surface model, but I am unsure how to classify ground points.

I looked into the lasground tool documentation, and noted that I can use a txt file as an input, but I'm not quite sure how that would work. Do I just batch process all of the text files using the lasground tool to output several thousand ground.las files? Can I mosaic those files? I guess I am just trying to put the data in a format that I can understand.

Thank you,

Jessica

[Olsen, Richard (RC) (CIV)]

Or we could provide Martin with some pcap data files, and the data format.

Actually, the PCL people have documentation (http://pointclouds.org/documentation/tutorials/hdl_grabber.php)  so it can’t be that far from a converter to LAS (or LAZ).

 

We have a V32 & V64, and can provide an ftp site for some representative data

 

RC Olsen

Naval Postgraduate School

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[Martin Isenburg]

Hello,

the best way forward would be to find a software (or write a tool) that can convert your points from the PCAP format to the LAS format. I am surprised the makers of the Velodyne scanners do not themselves provide a tool to convert the points their hardware captures into the LAS format - the most commonly used binary point data exchange format. I am cc-ing this email to the Velodyne LiDAR development team requesting that they add a LAS exporter to their software. But I am not a customer, so if you want such a tool and have more of their attention than me then I suggest that you email them as well. You have their address now ... (-:

(1) I suggest you create many many txt files containing the points in xyz or xyzi a layout (i = intensity). Maybe one file per driveline.

(2) Then you convert each of them to the LAZ format with txt2las using the '-parse xyz' or the  '-parse xyzi' option.

(3) Then you tile the resulting LAZ files into buffered tiles that have less than, say 10 million, points per tile with lastile.

lastile -v -i drivelines/*.laz -merged ^

          -tile_size 100 ^

          -buffer 5 ^

          -odir raw_tiles -o gmu.laz

(4) Then you refine tiles to 10 million points per tile if needed

lastile -v -i raw_tiles/*.laz ^

          -refine_tiles 10000000 ^

          -cores 4

lastile -v -i raw_tiles/*.laz ^

          -refine_tiles 10000000 ^

          -cores 4

(5) And then - starting from the tiles in the tiles_raw folder - you run one of those many tile-based batch processing pipelines for ground classification and DTM generation described previously in numerous tutorials, videos, and forum entries.

http://rapidlasso.com/category/tutorials/

http://rapidlasso.com/category/videos/

Regards,

Martin @rapidlasso

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