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).

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).

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).

Agisoft Photoscan Crash Course (updated for version 1.1.6)

Finally, time for an update…this time to Photoscan Professional 1.1.6. In this tutorial, I am going to fly through the basics of getting a Photoscan project up and running without getting to deep into the details. If you are interested in the details of specific tools, I will refer you to the official documentation (Agisoft Photocan User Manuals).

The instructions for the previous version 1.0 are still here…
I also have discussions on cameras and camera geometry.

Raspberry Pi Camera Extension Cable

I'm working on a project (hopefully to be completed this summer) that needed a longer, less rigid camera cable for my Pi camera board. I thought I would document this part of the project separately since it might be useful to others.

Desktop SfM Background and Scale

It seems like I've been doing/helping out with a lot of "desktop" structure-from-motion modeling. Through various iterations and attempts to scale the final SfM point clouds, the Van Gogh scale has emerged. So, I thought I'd share it in the hope that others can get some use out of it.

Maiden flight of our new UAV

A quick video of the maiden flight of our new DJI Inspire 1 quadcopter. We (the Dartmouth fluvial research group) will be using it this summer to do aerial surveys of several rivers throughout New England to look at dam removals, storm damage/recovery, and I'm sure much more.