I’m new to this game, but am interested in improving the mapping, so please forgive if I’m asking what has been asked before.
I’ve noticed quite a discrepancy in the OSM coastline in some place (my particular interest is Outer Hebrides) and am interested in correcting this.
If I go into Potlatch I get a Bing satellite image projection over the OSM coastline data, but I have seen copyright warnings about simply tracing from external sources. I’m also not sure if it is reasonable simply to drag the coastline line nodes in Potlatch to match a reasonable approximation of the sea/land border, given in particular that a walked survey is not viable for some of the more remote and dangerous cliff edges.
Hello Geoff, welcome to this forum and OSM in general!
You are right that we have to pay attention to copyright restrictions that prevent us from copying from most maps and databases. However, the good news is that some providers have generously allowed OSM to trace from their aerial and satellite imagery, and Microsoft’s Bing is among them. So you are allowed to align the coastline with Bing’s imagery.
When editing existing data, you should also make sure whether you are actually improving it. Generally, you can use your judgement: Is the previous coastline unnaturally shaped and only imprecisely mapped? If that’s the case, then moving existing nodes and inserting additional ones for precision is clearly a welcome addition. Otherwise, you would have to look into the situation in more detail, e.g. considering what sources the previous mappers used.
If you have more questions, feel free to ask! In the meantime, I wish you happy and productive mapping.
Thanks - in this instance the coastline is very clearly at variance with the real thing. I first noticed it in the TalkyToaster UK maps where the contours project into the sea, where the underlying OSM data on which these maps are based is inaccurate. I’ve also checked it against scanned versions of my own Ordnance Survey maps.