I did a demo the other day for some foresters and I almost wanted to walk into traffic by the end of it. Not because of anything with QGIS and LiDAR – but I think I finally got “Virtual Fatigue”.
Part of the demo worked amazingly well. If you’re not familiar with TN’s LiDAR Program most (I think all) of the state is covered in free LiDAR. Yes Free. You can grab a county’s worth of LiDAR data and get to work. Here’s the other thing you need to know – it’s in zLas format. Yes – zLAS – the most annoying of the formats. I have to uncompress it using LAS Liberator. Then there is about 20 minutes of hoping I’m not at the corner of 4 tiles. It’s painful.
PDAL has been the engine that has been making LiDAR viewable in QGIS for a couple of versions now. I don’t tend to use it a lot (because I don’t do a ton of work with LiDAR) but when needed it it’s invaluable. For me the entire crunch of doing anything with lidar has been:
- up to a 50 GB Download for an entire county
- Conversion from zlas to laz
- Define the vertical and horizontal projection of a tile using PDAL.
For the demo I wanted to do something “lidar” for a group of foresters to show them that FOSS4G works and we’re not just some weird hobby. I knew PDAL was being used on the backend of the USGS LiDAR Explorer but had not used it.
You can select an area (this is only for the US) and ONLY GET THAT AREA. I picked a pine plantation that had been partially thinned. I select the area using the interface. Choose my download format and PROJECTION PARAMETERS and then something cool happens. I generate a PDAL Pipeline JSON file and from the command line:
pdal pipeline process.json
I drag and drop the output of the above process into QGIS:
My life just got a lot easier and my blood pressure dropped like 10 points. LiDAR in TN is no longer a multi-hours scripted affair full of yelling. It’s literally pick what you want and then do the thing you want to do. QGIS gets easier. GRASS gets easier. Probably easier for the ESRI users also.
Anyway – check out LiDAR explorer from the USGS (especially if you’re in TN). It’s worth a few minutes of digging to learn about this tool.
