OpenStreetMap
Today was the usual mapping of buildings. When I went to upload these changes, however, quite a few warning signs came up regarding “tertiary road crosses river”. Usually only a few come up so I can click “ignore this issue” but today there were too many signs to ignore.
I can’t move or delete these rivers as I lack the knowledge on where these rivers run, and I also lack the geographical knowledge to predict where these rivers might run underground, if at all (I don’t move the roads as I can see them and know that they’re in the correct positions). I also don’t know where the mappers of these rivers got their information regarding the locations of the rivers underground unless it was first-hand knowledge from out in the field. If so, it begs the questions as to why there is a lack of labels on buildings nearby the rivers.
Perhaps this issue of roads and rivers crossing is something that mappers already look into at the validation stage. For what it’s worth, I have insufficient experience to be a validator as of yet. All in all I think it is a minor issue, but definitely something that should be looked into after the main bulk of a location is mapped.
Discussion
Comment from yvecai on 23 October 2019 at 18:41
All in all, underground rivers are not that common. Looking at aerial imagery, in most cases you should be able to spot a bridge or a ford, isn’t it ? In that case, split the road around the river and add bridge=yes, or ford=yes.
Comment from Warin61 on 23 October 2019 at 22:21
You can find details of things on the OSM wiki. Use it. But do think about what it says .. sometimes it does not make sense and then you should ask questions. As alway .. if you cannot make it out .. don’t tag it, leave it for others to add the detail.
Where you can see a bridge, map it
layer = 1 .. so it goes over the river bridge = yes .. generally, details ? https://wiki.openstreetmap.org/wiki/Key:bridge
If it is not a bridge, then it could be a ford or a culvert. A ford is where the river goes over the road - same layer so that does not need to be tagged. But if the river is a simple way then the ford should be a single node that both the river and highway share - and then tag the node as ford=yes. Only when the river has mapped river banks do you need to map the extent of the ford as part of the highway using a segment with the tag ford=yes.
See https://wiki.openstreetmap.org/wiki/Key:ford
If a culvert .. it is the river that goes into the culvert .. so tag that layer=-1 (goes under the road, some think that the river is actually layer=0 and the road should be tagged layer=1) tunnel = culvert
https://wiki.openstreetmap.org/wiki/Tag:tunnel%3Dculvert
Comment from Uyan on 24 October 2019 at 15:45
https://imgur.com/a/j48mTsW
Here is an example. I can see the river running through the middle of the blue oval (I circled the river), but it appears to tail off towards the ends of the oval. But the river is drawn across the whole map when I can’t see any clear indication of the river continuing.
(The picture comes from edits I made on 24th Oct 2019 around 1530 BST)
Comment from Carnildo on 24 October 2019 at 21:48
In this particular case, the best thing you can do is ignore it. Based on the available imagery, this is a very minor stream that is mostly not visible from above. In order to get the routing correct, it needs to be mapped on the ground, by someone following it with a GPS.