Here’s a secret from bloggers: we get a tally of how many times each page or post gets clicked on our sites. This year I’ve gotten a lot of readers clicking on my older SAGA articles, so it seems like a good time to share some of my favorite SAGA resources even though it’s not a software I’ve been using for much of my current work.
The first resource I’d like to highlight is this SAGA Tutorials Blog. I’m not sure who runs it or how frequently it’s updated, but their tutorials are detailed, well-organized, and extensive. I’ve mostly used the Terrain Analysis section, but their intro materials are also great. If you’ve tried downloading SAGA and are struggling to get started, I’d highly recommend their Layout post– it’s a quick read and helps clarify the less intuitive menu bars. The next place I’d direct you towards is their Importing Data tutorial so you can start playing with your own data.
As you import data, you’ll notice that SAGA uses a data format called “Grids,” which are different from GeoTiffs or other raster formats. I have an overview of the data format in a post blog post (Intro to SAGA GIS), but it’s worth reiterating here too. In the photo to the left of a data layer in SAGA, there is a single layer in a single grid system. The grid system is defined by a series of numbers. The first number represents the resolution in the units your data is projected in (mine is 2.5 feet). The next numbers are the extent of your data in cells wide by cells tall (my data is a 2000x 2000y square). The next numbers are the origin, or starting point, of your data. This data is in a foot-based projection of NAD83 for Northern Ohio, so the 7 and 6 digit numbers seem right. Under the grid system, you can see an individual data layer. The only layer in there right now is “mtgileadelevation.” As I generate more layers using terrain analysis tools or other SAGA algorithms, all the layers that share the same resolution, extent, and origin will populate under the same grid system.
I mostly use SAGA for terrain analysis, but it can do pretty much anything you’d do in a GIS. If you get started with SAGA and really love it, it’s worth exploring some of the georeferencing and map layout features. The most detailed resource I’ve found on these topics is the SAGA Manual by Víctor Olaya. The intro chapters are quite lengthy and include a good mix of detailed descriptions and helpful screenshots– definitely check it out you’ve found the SAGA Tutorials blog or my posts to be insufficiently detailed.
If you’re interested in SAGA algorithms but don’t want to invest time in a new software, the SAGA for QGIS plugin is also great. This is also a great option if you find the grid systems organization to be confusing. For regular QGIS users, the QGIS documentation page for the plugin might be enough to get you started. If you’re looking for a detailed tutorial, I’d recommend The Use of SAGA GIS Modules in QGIS by Paul Passey and Sylvain Théry (it’s available for free on ResearchGate here). I hadn’t considered using the plugin for vegetation indices before reading their article, but now I definitely want to try it.
SAGA isn’t the most intuitive software to learn, but I’ve found it to be valuable in my research. With these resources, you can overcome the initial learning curve and start using SAGA for raster data handling. I’m also always looking for more SAGA tips and tricks, so if you have any favorites I’d love to hear about them in the comments!
Spatially Challenged 