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I am aware of WHODIDIT, which lets you monitor changes in a given area, but I would like to monitor changes to a list of specific relations and ways (a few hundreds of them) which are not necessarily close to one another. For example, I would like to know when the boundary of a certain city is modified. Is there any tool that allows you to do that? |
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Overpass API can indeed help, at least starting with v0.7.50. As an example, you could query for changes to ways 5000000 + 5000001 (including their nodes) since January 1st 2012: Try this on turbo and switch to the Data tab to see old/new data as well as the type of change (create/modify/delete). Note that there are no changes shown for way 5000001 as there weren't any in the last 5 years. Also some of the changes may no longer be available due to the License redaction bot. As a general rule of thumb, all changes since September 2012 should not be impacted by the bot. For advanced visualization of augmented diffs please refer to Overpass Turbo Issue #80 (in planning phase at the time of writing this comment).
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This answer is marked "community wiki".
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Maybe you are able to load each relation element from the main OSM database with full meta data. This should include the version number of each object, and if I am not wrong even a timestamp when it was modified the last time. Each time when an OSM object is edited, the version number is increased by 1. Try to store the version number of each object in a file or database of your choice. Then compare that stored version number with the result when you want to check it. Perhabs you can benefit from the famous overpass-api. |
Be aware that this involves more than just the relation and ways. A boundary also changes whenever one of the way's nodes get moved. But changes in the position or the tags of a node are not recorded in the way's history. So you way want to monitor each single node, too.
This is exactly covered by the Overpass API example I provided below. You just have to define which objects (and depending objects) you want to include in your change analysis.