Friday, August 26, 2016

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). I
t 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.

Tuesday, January 12, 2016

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)

Friday, December 4, 2015

GIS Change Detection Math

I do a lot of topographic\geomorphic change detection, mostly with raster digital elevation models but I've also started getting into point cloud differencing too. It's simple subtraction, but the way you do your subtraction can make a big difference in how you interpret the data. I've had several students ask about this, so I thought a short write up was in order. The examples here are topographic (erosion and deposition), but the concepts apply to any raster-based change detection (i.e. land use/land cover change).

Tuesday, August 18, 2015

Calculating Spatial Resolutions for Aerial Imagery

I've often needed to calculate/predict the spatial resolution for aerial imagery collections that I do (the life of a remote sensing researcher). I wrote a Matlab script for some helicopter aerial photography as part of my dissertation research. But, I needed a more streamlined script for some of my current work with UAVs. So, here is a brand new Python script to do all the calculations for me (and you).

Thursday, July 30, 2015

Strapping a NIR Camera onto the Inspire 1

I finally went and did it...strapped my near-infrared camera (NIR) onto our DJI Inspire 1. Here are some of the results from this quick test flight.

For those unfamiliar with NIR imaging, in Geography we primarily use the near-infrared portion of the spectrum to help us measure a multitude of things just beyond the visible portion of the electromagnetic spectrum. Some of the primary uses for NIR imaging are to measure vegetation types, vegetation health, and help differentiate different landuse/landcover types. Here's a NASA link to more information on NIR and another on the Normalized Difference Vegetation Index (results below).