Sometimes it takes a while to follow up on a blog post. A while back I wrote more or less “I got me some LIDAR what can I do with it?”. Well…..
First I need to learn about LIDAR and at some point (probably during Part 3) names will be named. There have been several people in the FOSS4G world helping me move along and learn.
Second thing I needed to do was ask questions. I asked a lot. I learned:
- TN has been participating in 3DEP. So this LIDAR Data (as well as several other products) are coming from that program.
- I need to read metadata.
So when I left you on my original post I was importing LIDAR into GRASS and somewhat failing miserably. After reading the metadata the point data was classified as follows:
Class 1 = Unclassified. This class includes vegetation, buildings, noise etc.
Class 2 = Ground
Class 7= Noise
Class 8= Model Key Points
Class 9 = Water
Class 12=Overlap Points (high scan angles)
Class 13= Bridge Deck Points
So this gets a little bit easier. Using v.in.lidar I can now build a DEM and pull the values coded for bare earth straight in.
Hillshaded for posterity:
Once I started “playing” fun things started happening. I know this isn’t 100% right because I have more to learn. What if I import LIDAR data coded as vegetation and subtract that from the DEM. I have Vegetation height. With the Ortho image I can shove more knowledge toward my foresters. I also have some negative values I’m going to investigate.
You may be going “Well that’s great you’re sitting here doing crap anyone can do”. Possibly. For a small entity with limited budget you can whip out GRASS and start doing things. This was a 10 minute endeavor for one tile. I also generated slope and I’m working on building a solar radiance map of the area. Now I want to process the entire county for elevation. Can I? I will also dump this out to QGIS because I can.
The big kicker in all of this THIS IS FREE DATA. Well – except for the zlas problem. State of TN – take the lead and open the format for the users. Switch to las.
So what am I doing for Part 3:
- Upgrading GRASS to 7.2 (I’m running 7.0.4)
- Count LIDAR points on the ground – the metadata claims one point per meter.
- Will someone give me the RAW data? I’m attending a conference where people of influence will be – I’m going to ask.
- Building Height with elevation above ground?
I have a lot to learn and I am by no means an expert. LIDAR started getting popular about the time I walked out of my federal job and I never have clients that go “We’ve got this data sitting around”. I’ve never had to deal with it but now that I have a source to work with there’s a lot I can do. I have a community of people that will answer questions when I have them. Never stop learning.
Anyway – Part 3 is coming and it won’t take months for me to get to it.