What or who is our source?
When we map, we use something (or someone) to base our mapping on. Preferably in such a way that other mappers can verify what we added to the map.
To help with that task, we are requested to add a source=* tag to whatever we put on the map.
What are the most frequent used sources on OSM?
The top 3 (all used more than 10 000 000 times):
1. BAG - 18 840 435
2. cadastre-dgi-fr - 12 150 135
3. Bing - 10 695 411
You can see the full list on taginfo yourself.
The tag source=* can be used in numerous combined tags (like source:date) as can be seen here.
For this article I only used the plain source=* tag.
However, I was not interested in the source=* tags that were most used, but on the ones used less. And even more so in source=* tags that were incomprehensible. For instance, what should we think of this: Am I supposed to call that telephone number if I want to check the details?
I found quite a few instances of such source-tagging where a telephone number was used. And quite often this was used on bars and clubs. Some of them "members only".
A telephone number is at least something that could be used as a source of information, although it is not very informational. But what about this one? What source of information is hidden in 0,4? This one is also not very helpful: And sometimes mappers have some sense of humor, like: "Q" (think James Bond) is of course a wealthy source of information: And this one surely used a source, but left us just guessing: And this one? It is clearly a mistake, because the mapper use a colour code in the source field. Finally, the weirdest I saw: I contacted the mapper to ask what it meant, and it must have been some mistake. He maybe corrected it already at this time. To see to the situation it refers to, check this.
The list is endless, sometimes hilarious, but should we do something about it? I don't think so, relatively those errors are a minority, because they are used very seldom. Mostly just once, hence they don't take up very much space.
But using a reliable, understandable source key, would surely help improving OSM! Think about your source the next time you let other mappers now where your data came from!
All screenshots with openpoimap.