A quick post today to talk about a couple of PostGIS functions I learnt recently. I had a CSV file that contained well-known binary (WKB) representations of geometries, stored as hexadecimal strings. I imported the CSV into a PostGIS database, and wanted to convert these to be proper PostGIS geometries. I initially went for the […]
Microsoft Planetary Computer is a wonderful archive of geospatial datasets (primarily raster images of various types), provided with a STAC catalog to enable them to be easily searched through an API. That’s fine for normal usage where you want to find a selection of images and access the images themselves, but less useful when you […]
For a while I’d wished there was an easy way to get notified when my favourite open-source packages release a new version. I’d often see something on social media, but that tended to only be for the larger packages – and I wanted to keep up with the smaller ones too. When I actually bothered […]
I was looking through my past blog posts recently, and thought a few of them were worth ‘reblogging’ so that more people could see them (now that my blog posts are getting more readers). So, here are a few posts on matplotlib tips. Matplotlib titles have configurable locations – and you can have more than […]
I had a need to do some segmentation of some satellite imagery the other day, for a client. Years ago I was quite experienced at doing segmentation and classification using eCognition but that was using the university’s license, and I don’t have a license myself (and they’re very expensive). So, I wanted a free solution. […]
Summary: You can use QGIS expressions to set the default path for an Attribute Form to be something like @project_folder || '/' || 'MapGraphs', which gives you a default path that is relative to the project folder but also has other custom subfolders in it. I spent a while redrafting the title of this post […]
I came up with an interesting plan for an artistic map recently (more on that when I’ve finished working on it), and to create it I needed to be able to calculate a large number of driving routes around Southampton, my home city. Specifically, I needed to be able to get lines showing the driving […]
This is a bit different to what I usually post on this blog (which is usually technical content about GIS, remote sensing, Python and data analysis – see a few example posts), and this is part of April Cools – a group of bloggers writing posts that are unusual for them, but still good content. […]
Here’s a bit of SQL I wrote recently that had an error in it which I struggled to find. The error I got was ERROR: invalid reference to FROM-clause entry for table "roads" and I did some Googling but nothing really seemed to make sense as a cause of this error. My SQL looked like […]
Summary: It might be because there is an exception raised when importing your function_app.py – for example, caused by one of your import statements raising an exception, or a parsing error caused by a syntax error. I was deploying a FastAPI app to Azure Functions recently. Azure Functions is the equivalent of AWS Lambda – […]