feat: Add post improve-osm-by-using-it

content/post/improve-osm-by-using-it/index.md

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+---
+title: "Improve OpenStreetMap data by using it"
+date: 2025-04-16T12:10:10+02:00
+draft: false
+image: "post/improve-osm-by-using-it/improve-osm-by-using-it.png"
+categrories: ['English']
+tags: ['django', 'OpenStreetMap', 'notfellchen', 'osm', 'open data', 'geojson']
+---
+
+## Introduction
+
+In the last month I improved the mapping of about 100 german animal shelters - not only out of the goodness of my heart, but because it helped me.
+
+Let me explain why: I develop [notfellchen.org](https://notfellchen.org/), where users can search animals in animal shelters, specifically rats, they might want to adopt.
+The idea is to have a central website that allows you to search for rats in your area.
+
+This is necessary because only a small percentage of animal shelters has rats. As a user, just checking your next
+shelter doesn't work. Some users will stop after checking the second or third one and just buy from a pet shop (which is a very, very bad idea).
+
+Now a central platform for is nice for users but has one problem: How do I, as operator of notfellchen, know where rats are?
+
+I need to **manually check every animal shelter in the country** and if they have rats, ask them for permission to use
+images of the rats on my site.
+So wait I need to have is a list of animal shelters in germany and have their website, e-mail and phone number.
+
+The source for all of this: You guessed it - OpenStreetMap 🥳
+
+
+# Getting the data
+
+Downloading all german animal shelters is surprisingly easy: You use [Overpass Turbo](https://overpass-turbo.eu/) and get a `.geojson` to download. 
+
+here is the query I used:
+
+```
+[out:json][timeout:25];
+// fetch area “Germany” to search in
+{{geocodeArea:Germany}}->.searchArea;
+// Check search area for all objects with animal shelter tag
+nwr["amenity"="animal_shelter"](area.searchArea);
+// print results
+out geom;
+```
+
+Now upload it to notfellchen.org and I'll be fine right?
+
+# Data Issues
+
+Yeah well, this only *mostly* works. There were two main problems:
+
+**Missing contact data** is annoying because I quickly want to check the website of animal shelters.
+
+rMore annoying were what I'd call **mapping errors**.
+Most commonly an animal shelter had multiple nodes/ways tagged as `amenity:animal_shelter`.
+The highlight was the "Tierheim München" where about 10 buildings were tagged as `amenity:animal_shelter` and the contact
+data was sitting on the building with name "Katzenhaus" ("cat house").
+
+Now the "Tierheim München" appeared in my list 10 times but 9 of them had no contact data at all. 
+
+# Correcting it
+
+I could have corrected this only in the notfellchen database. It would have been faster and I could even automate parts of it.
+But I didn't.
+
+For each issue I found, I opened OpenStreetMap and added websites, phone numbers or even re-mapped the area.
+For "Tierheim München" I even [opened a thread in the forum](https://community.openstreetmap.org/t/mapping-of-multiple-related-buildings-animal-shelters/131801)
+to discuss a proper tagging.
+
+That makes sense for me because I get one important thing:
+
+# What I get out of it: Updates
+
+What if a new shelter was added later or a shelter changed? I already profit a lot from the time people spend adding information, so why stop?
+
+My database stores the OSM ID, so I can regularly query the data again to get updates.
+But that only works if I take an "upstream" approach: Fix the data in OSM, then load it into notfellchen.
+Otherwise, any change in my database will be overwritten by "old" OSM data.
+
+# Result
+
+In the last month, I made 86 changes to OSM adding the following information
+
+| Type of information | Number of times added | 
+|---------------------|-----------------------|
+| Website             | 66                    |
+| Phone Numbers       | 65                    |
+| Operator            | 63                    |
+| E-Mail              | 49                    |
+| Fax                 | 9                     |
+
+Yes I sometimes even added fax numbers. It was easy enough to add and maybe there is someone might use it.
+
+# Looking forward
+
+I'm of course not done. Only half of the rescues known to OSM in germany are currently checked, so I'll continue that work.
+
+After that I'll start adding the shelters that are just in my database.
+Currently, 33 animal shelters are known to notfellchen that are not known to OSM. This number will likely grow, maybe double.
+
+A lot to do. And luckily, this work both benefits me and everyone using OSM. Happy mapping!