I live in Lausanne, Switzerland, and I would like to buy a home in the next years or so. The market is so hot that as soon as a new home is on the market it gets sold in days. Hence I would like to have a clear vision of the homes that are going to be build in the next years. Luckily enough the city in which I live is providing such information through a website:



If you go to that page you will see a map of the canton of Vaud. In the main menu click on Thème: Localisation > Permis de construire

enter image description here

Now under Données on the right side menu untick "Zone d'affectation"

enter image description here

If you zoom on Lausanne you will now have a map that looks like this:

enter image description here

This map is updated every 2 weeks and you will see new dots added and old dots leaving.

Before I start to write a custom web crawler in Python I would like to know if there is any solution out-of-the-box that could help me identify the difference between this map and how it was last month. A sort of diff command for web pages.


I'm dealing with the web page owner to see if the have an available API and they haven't replied me yet. That would be my solution.

Otherwise do you know what is the map used in this website? It doesn't look like OpenStreetMaps to me. If I know the framework maybe I could understand how to reverse engineer the content of the page and maybe export in CSV, XML. JSON, etc...


I'm all ears, tell me how would you approach this problem or if you know any tool that could help me archive what I want.

1 Answer 1


Hopefully someone will be familiar with software that does exactly what you want out of the box. In the meantime, here are recommendations for 2 tools that may help you achieve your goal.

For detecting changes to web server responses (incl API responses), WebChangeMonitor is excellent. It is cross-platform, and will run on Linux, Raspberry Pi, and Windows.

It is open-source and is available here:

For detecting changes to saved images, WinMerge is quite good. Unfortunately, it is Windows-only. I have yet to try in under Wine in Linux, but I've heard it works well.

It is also open-source and is available here:

Neither does exactly what you want, but maybe you can use one or both as tools for your interesting project.

Good luck!

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.