Since I mentioned kernels last week, I figured this would be a good time to go over the geographically weighted regression (GWR) procedure in SAGA. Once again, I don't have good example data I can post online for this topic, so you'll have to forgive the lack of pictures. GWR is an interesting method with… Continue reading Geographically Weighted Regression in SAGA
I broke out SAGA again this week to do some soil interpolations. I don't usually use inverse distance weighting (IDW) for much because you can't generate error maps or use covariates with this method. For this project I needed to make some maps in IDW to compare back to other methods. I'm using IDW for… Continue reading Inverse Distance Weighting in SAGA
Curvature, the second derivative of elevation, is a very useful terrain derivative. It describes how convex or concave a surface is, which helps predict soil moisture (among other things). The basic terrain analysis feature in SAGA calculates plan curvature and profile curvature. Profile curvature goes with the direction of maximum slope, which helps estimate acceleration… Continue reading Types of Curvature
Last month I shared some ways to calculate terrain derivatives in SAGA, focusing on the Basic Terrain Analysis function. Today I'm going to give you a quick overview of what each derivative means and some of its potential uses. Let's start with the most intuitive ones. Slope is how fast elevation is changing. A higher… Continue reading Defining Common Terrain Derivatives
If you missed my posts on terrain derivatives or SAGA, you may want to jump back and read those first. Today I'm going to talk about two very common terrain derivatives and how to calculate them in SAGA. I'm going to keep going with the same DEM from Mt. Gilead State Park I used in… Continue reading Basic Terrain Analysis: SAGA
Last week I mentioned terrain derivatives and promised some how-to posts. I'm going to start with an brief intro to SAGA GIS, which is my preferred software for generating terrain derivatives. SAGA was written in the early 2000s and has been regularly updated-- you can learn more from its makers here. You can download SAGA… Continue reading Intro to SAGA GIS
Lots of people have been asking me about terrain derivatives lately, and I've been putting off blogging about them for a while because I just didn't know where to start. Instead of one master post with all the things I decided to split it into some more manageable chunks-- for both your sake and mine.… Continue reading What are terrain derivatives?