Posts

Short answer: your GIS software needs to fill the blanks in the area with NoData pixels. Long answer: I will demonstrate what happens by an example on QGIS 3.18, and show why the final raster tends to be larger than the other two summed.

Today, I am going to show you how to georeference an image using QGIS 3.18. Maybe you found this image in a paper, or maybe it is an aerial photograph. It doesn’t matter! If you know the coordinates of at least two non collinear points, you can add geolocation to the image!

Today, I am discussing different ways of cutting (clipping) a raster in QGIS and what they do. Especially, I am comparing QGIS GDAL tools “Clip raster by mask layer”, “Clip raster by extent” and “Warp (reproject)” in what are they used for, and what exactly do they do to the original raster data.

Today, I am going to write about how to open, edit and save raster files using Python if you are familiarized with Python (mainly Anaconda). Maybe you need to run every pixel in a raster through a Python function, or you want to do custom operations with them that are not available on GUI software such as QGIS. It also can be used to do batch processing. We are going to use GDAL on Python, installed through Conda, to do this.

Azimuthal maps are certainly more common in the northern hemisphere, but they can be done for the southern hemisphere as well. They can be useful for localizing places in Antarctica, South America, Africa, and Oceania. These maps can be included in scientific publications or presentations. Last week I presented my research in the EGU General Assembly 2021 and part of the location map was prepared in South Pole azimuthal projection. These steps are the basics of how to make an azimuthal map for South Pole.

One of the simplest yet most tricky ways of doing batch processing is by using Bash scripts. Bash is a type of Shell Script, which means it runs directly on a user interface that accesses the services of an operating system.

Today, I am going to write about the batch processing of loading and altering the symbology of a big group of raster layers on QGIS. This tutorial was made on QGIS 3.18 Zürich, using its Python Console to load the layers.

Today, the post is about how to generate the raster for Vertical Distance to Channel Network (VDCN) using QGIS Raster Calculator, and SAGA on QGIS or command line interface (CLI), step-by-step. Vertical Distance to Channel Network (VDCN) is the vertical distance to the interpolated Channel Network, or the river network of the location.

Last week, we talked a little about using SAGA on Command Line. Today, I am discussing solutions to the problem “Error: Catchment Area” on SAGA GIS. Or “Error: your input raster”, or “Input layers do not have the same grid extent”.

SAGA also has its own Graphical User Interface (GUI). And it also has its own Command Line version. One may ask, why would someone deliberately choose to use a Command Line version in detriment of a GUI? Well, a GUI uses its own share of memory, CPU, sometimes GPU, to run.