QGIS

When I mosaic two rasters, the size of the resulting raster is almost always larger than the sum of the sizes of the original rasters. Why is that?

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.

How to georeference images using QGIS 3

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!

How and when to use QGIS 3 tools “Warp (reproject)”, “Clip raster by extent” and “Clip raster by mask layer”

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.

A simple tutorial for generating a South Pole Azimuthal map on QGIS

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.

How to load (many) raster layers on QGIS 3.18 by batch process and alter their symbology together

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.

Guide to calculate the Vertical Distance to Channel Network (VDCN) step-by-step, tutorial using only open-source GIS software QGIS and SAGA GIS

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.

Solved: SAGA GIS 7.9.0 and 2.3.2 (in QGIS) input error “Error: Catchment Area” on the execution of LS Factor “saga_cmd ta_hydrology 22” and other algorithms

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”.

How to use SAGA GIS Command Line saga_cmd, and why?

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.

A quick guide to generate continuous raster legends in QGIS 3.18 Zürich – and in QGIS 3.16.4 Hannover

A functionality to show continuous color ramps automatically was implemented in QGIS 3.18 “Zürich”. The QGIS 3.18.0 standalone installer was just released Windows users, in March 22th.