Solving a “gaps and islands” problem using LAG [SQL]
At my work, we have a lot with sensors installed all over the city, which take measurements at certain intervals, e.g. once per minute. For example, a water sensor, which every minute measures the current level of rain water in an underground basin. Most of the time the sensor will measure zero amount of water.…
How to make a non-rectangular map layout in QGIS
Rectangles are the most common shape of maps in GIS software, but why stop there? In GIS software like ArcGIS Pro, it is possible to create map layouts in non-rectangular shapes without too much hassle. But that is not the case in QGIS (yet!), so let’s look at ways to make creative map shapes in…
How to download a satellite image from Copernicus Open Access Hub
Personally I don’t find the Copernicus Open Access Hub very intuitive to use, so I wanted to provide an example of how I download data from the website. For this example I want to download a single Sentinel 2 (A or B) image from the northern part of Jutland in Denmark. I want it to…
How to find a specific satellite image in Google Earth Engine
Let’s say there is a specific spatial event that you are interested in, for example the volcanic eruption in Tonga on January 15th in 2022. For this example I will use data from publicly available polar orbiting satellites. These kind of satellites only take a single image of an area, and returns to that area…
Visualising the age of buildings: Copenhagen [QGIS]
Through the exellent newsletter quantum of sollazzo by Giuseppe Sollazzo (@puntofisso) I learned of the beautiful map of Paris by Naresh Suglani (@SuglaniNaresh), where Suglani have visualised the year of construction in a lovely blue-to-red colour gradient. It is a stunning visualisation, and I immediately wanted to try to make a similar version myself. Here…
Using the Attribute Based Clustering plugin [QGIS]
QGIS is not as easy to work with regarding spatial statistics as its commercial counterpart ArcGIS. However, QGIS does have some plugins that can do some great statistical analysis. One example is the Attribute Based Clustering plugin, created by the QGIS-contributor ekazakov. The plugin creates clusters based on the attributes of a vector layer, not…
SMAP soil moisture data now available at 10km resolution [Google Earth Engine]
I realise that I am a bit late to the party, but I just noticed the paper by Mladenova et al (2020) which outlines a new SMAP-based soil moisture dataset, where the resolution is increased from 0.25°x0.25° (roughly 27-28km at the equator) to 10km by “assimilating soil moisture retrievals from the Soil Moisture Active Passive…
Time series for SSM, ET and precipitation for Myanmar [Google Earth Engine]
Back in December 2018, I was in Yangon (Myanmar) to help facilitate a workshop on satellite-based remote sensing to support water professionals in the country. For this workshop, I created a script to calculate a time series for surface soil moisture, evapotranspiration and precipitation. The data for this script are: Large Scale International Boundary Polygons…
Map examples
Here I will post examples of maps and other images that I have created. Feel free to ask about how certain elements were created, and I can make a post about it. I will update this post when I have new content to show.
Calculate the percentage (%) cropland for each polygon in a shapefile [Google Earth Engine]
In a previous post, I use a similar script to calculate NDVI per polygon. However, this script includes a small difference which I have not yet myself understood why it was necessary. As before, my shapefile consists of the administrative borders of Tanzania. I got this shapefile from the GADM database (version 3.6). Now I…
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