I am sharing this resource now because I just remembered how great it was while taking about SQL with a friend, and now I honestly feel bad that I haven't shared it with readers before now. If you aren't familiar with open courses, they are free, online ways to learn new skills. They vary in… Continue reading Stanford Open Courses
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Geographically Weighted Regression in SAGA
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
Making Box Plots
Last month I posted about how to read box plots, and today I'm sharing how you can make your own. I picked two online tools that don't require you to calculate the mean and quartiles yourself and shared a quick couple lines of code for the R users out there. Let's start with Desmos! Desmos… Continue reading Making Box Plots
Data Downloads: Soil Maps
Today I'm continuing a series on sources of spatial data (see past posts on aerial images and DEMs). Soil maps are useful for all sorts of applications, like deciding where to place a trial in a larger field so that all the treatments are on the same soil type or determining the drainage class of… Continue reading Data Downloads: Soil Maps
Inverse Distance Weighting 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
Saving Layer Style Files in QGIS
Sometimes getting a layer to be displayed precisely how you want it can be a tedious process in QGIS. Fortunately, there is a way to save that style so you can apply it to the same layer in another project, or to another layer with similar attributes. Most of the time I use layer style… Continue reading Saving Layer Style Files in QGIS
Types of Curvature
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
Getting Category Colors into QGIS from ColorBrewer
Are you as obsessed with ColorBrewer as I am? I am making a map where I color Ohio counties based on region, and used ColorBrewer to pick colors. The first thing I did was go to ColorBrewer and find a qualitative color set for 5 categories of data. Next I used the HEX codes provided… Continue reading Getting Category Colors into QGIS from ColorBrewer
Basic Terrain Analysis: SAGA
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
Intro to SAGA GIS
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
Spatially Challenged 