Filtering LiDAR data by height above ground

For this tutorial we will be using CloudCompare (version 2.8, cloudcompare.org)

Lidar point clouds normally come with elevations above sea level (or some other datum), which is 
extremely useful. However, we can convert the Z-values into a height above the ground as way to add another layer of data so that we can measure things like average tree heights, examine building heights., or (one thing I do a lot) filter the points to so that we only see points in a specific height range above the ground. This last application is what we'll be covered here and it's really useful to examine river channels below dense vegetation.

New Job!!!

This summer I'll be transitioning away from Dartmouth to a tenure-track position in the Geography Department at the University of Northern Iowa.

I've updated my contact info on my About Me page.

New Articles

Here are two recent articles that I was working on over the summer, both in Earth Surface Processes and Landforms. Enjoy!

Dietrich, J. T. (2016) Bathymetric Structure from Motion: Extracting shallow stream bathymetry from multi-view stereo photogrammetry. Earth Surface Processes and Landforms, doi: 10.1002/esp.4060.
http://onlinelibrary.wiley.com/doi/10.1002/esp.4060/abstract

Carbonneau, P. E., and Dietrich, J. T. (2016) Cost-effective non-metric photogrammetry from consumer-grade sUAS: implications for direct georeferencing of structure from motion photogrammetry. Earth Surface Processes and Landforms, doi: 10.1002/esp.4012.
http://onlinelibrary.wiley.com/wol1/doi/10.1002/esp.4012/abstract

New Off Nadir Resolution Calculator

A quick update, I uploaded a new Python off-nadir resolution calculator to my GitHub:

https://github.com/geojames/py_offNadir_Res

It only works for low-oblique images (theoretically it would also work for nadir images if you set the pitch of the camera to zero). It calculates the pixel resolutions for the near field (closest to the camera), mid field (at the principal point), and the far field (furthest for the camera). It will also tell you the area that each image covers.

If your interested in how it works head over to the GitHub repository.

Amethyst Brook Dam Removal

Some footage from last week's dam removal on a stream that we (Dartmouth) have been doing extensive monitoring on in West-central Massachusetts (near Amherst).

More photos of the site post-removal are here: https://goo.gl/photos/xxTxe34HzTcnPozr8 (some are thanks to Alex Hackman of Mass. Fish and Game)