At the TNGIC conference I did a workshop on LIDAR and QGIS. I was completely blasted out by ESRI’s Avenue for the Web class but I had a few souls come in and take a look at it. I finished it off with “I don’t use LIDAR that much”. Well…..I’m finally using it.
It took a lot of convincing but the last two forestry jobs have involved LIDAR. Yesterday’s job was interesting enough to warrant me scribbling something down.
In the following pic you’ll see a boundary and NAIP imagery…and a few red polygons. The red are recent tree planting areas. The question is “How tall are the trees?”. Using my foresters brain he determined that the 50 foot tall trees could work for this weird carbon credit thing the land owner was going after. LIDAR will give us an approximate height. Except in TN the LIDAR for this county is 9 years old. How fast do trees grow? It depends so we guessed a foot or slightly more a year for pine and “It depends” for hardwood.
QGIS makes it easy to get a Height Above Ground. PDAL makes it easy with the pipeline approach but having a menu for spur of the moment analysis makes life easier. The darker the image the higher the trees. The trees in the image below top out at 140 feet. We are looking at anything over 35 feet.
So lets do a height above ground and pull the values greater than 35 feet out.
With the imagery and the tall trees in yellow:
Knowing what my my exceptionally small forestry client that just utilized lidar knows, nothing has been done to this tract in 10 years except the areas in Red. So does the land owner have the percentage of 50 foot tall trees he needs? No.
We determined all of that without killing a day or two out in the field driving around. Instead he’s going to take a day and make the tract better through management and planting and whatever else needs to be done. He will also spot check this map to see how wrong or right I was in this analysis.
LIDAR acquired here: https://apps.nationalmap.gov/lidar-explorer
Parcels: https://comptroller.tn.gov/office-functions/pa/gisredistricting/redistricting-and-land-use-maps.html
