Can anyone explain how this makes any sense?
(The magenta way is highway=track with a custom paint style.)
unfamiliar with this location, unable to check data or other aerials etc given no location info…
but I seen places where such mapping would be entirely correct (stream crossing twice the track, another waterway forming third ford shortly after)
giving info where you found this case would be really helpful (maybe it is dry area where streams are very implausible? it kind of looks like small patches of vegetation in dry area, but again without location info it is hard to say anything)
This is in the vicinity of Bishop, CA which has an annual rainfall of 5.25" (about 13 cm). Here’s one of the “ford” nodes: Node: 910025940 | OpenStreetMap
The waterways are NHD imports, so it’s questionable whether they’re actually in the right place. But from the Bing imagery, there’s no appreciable flowing water at this location. If there were, we would see:
- Either more vegetation where it could use the water to grow, or less vegetation where the flowing water would wash away smaller plants
- Some signs of erosion on the track and in the surrounding terrain since the soils here are generally coarse to fine alluvial deposits that are relatively fragile
[Edit] And the track is unimproved native material.
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Without pointing fingers, but that’s a perfect combination of importing low quality data and using MapRoulette on fixing resulting bugs.
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Not just MR – iD and JOSM are just as aggressive about suggesting ford=yes.
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Indeed, I should have wrote QA-tools in general. At least in the US, most likely the NHD-waterway or the Tiger-highway is the issue, not the missing ford.
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It doesn’t
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The location of this waterway (if it is a waterway) seems to be in generally the right location, but not necessarily precisely placed: Way: 77332266 | OpenStreetMap This is based on the USGS 3D Elevation Program Contours.
I would say given the lack of precision, it is highly likely that the waterway does not intersect the track at these two locations:
or that the water, if it is ever present, flows down the middle of the track.
But I agree with you, there is probably hardly ever any water here.
This waterway doesn’t seem to exist (and would not exist even during the heaviest rain storm):
again, based on the 3DEP contours.
The problem you have pointed out is a general one I have seen a lot of, people adding fords simply to make some error message go away, and not doing the necessary research to determine what is the real situation.
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… and creating a ford to make the message go away is equivalent to putting tape over the check engine light in your car… it doesn’t really fix the problem.
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Is there a way to correct these misplaced fords that will not cause editors and QA tools to suggest adding them back?
(Other than realigning the waterways so they don’t intersect the highway, which might partly work here but doesn’t work in general.)
I’ve only seen iD and JOSM suggest adding a ford when a highway and waterway cross each without intersecting. I haven’t seen such a suggestion when they intersect at an untagged, shared node. I don’t know about other QA tools.
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Though they warn about crossing highway/waterway (and the easiest fix is to add the crossing note and define it as ford). That was the reason I mentioned MR in the beginning, since you want to solve the issues fast to score more points.
This sort of works. But gluing the highway and waterway together when the alignment of both ways is questionable is not ideal.
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Well, after trying to create highway/waterway intersections with untagged nodes in some real world scenarios, I have decided that this is also complete nonsense.
Many of these small, dry “waterways” are indistinct and on relatively flat terrain, so it is impossible to verify their location using even good quality aerial imagery and 3DEP contours. This means that the location of these “waterways” is arbitrary, and so the intersection nodes are fictitious.
This approach of gluing the waterway to the highway is completely impractical in cases where the two follow the same general path though a canyon or wash. Adding dozens of fictitious intersection nodes simply to appease the validator doesn’t make sense and is adding no value to the map.
The best approach I’ve found so far is just to silence the validation of highway/waterway intersections. Unfortunately, this doesn’t work for mappers who aren’t thinking things through and just follow what the validator says.
So, the next time someone comes through the same area, they’ll add all the nonsense ford=yes nodes to make the validator happy.
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I would rather say, if there is no waterway (or traces of it) visible, then there should be neither a waterway in our database.
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I just voted you up, mind you, there are seasonal or intermittent streams, so this should NOT serve as an argument for deleting “waterways” on single sight. Streambeds have a certain look, even if dry.
I like the sentiment, but I worry that some of these “waterways” could be identified on the ground even if they are not discernible in aerial imagery.
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I just returned from a trip through the desert where I was able to ponder features like the one pictured below. The photo was taken from a dirt track at 36.757984, -116.661699 looking SW at a supposed waterway mapped in OSM.
After further consideration, I think the issue is not whether there is a “ford” at the intersection of this “waterway” and the track, but whether this is a waterway at all. Instead, I think this might be better mapped as natural=gully, for which no ford is necessary.
As the OSM wiki says: " A gully is a small scale land form (a few to a few tens of meters) incised into surrounding terrain through erosion by flowing water."
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Yes!, and even in the cases where there is a waterway, it is often mislocated by 10s of meters, as is the trail/track. Also in many cases mappers have inserted fords in the data where there are bridges or culverts in reality because they are guessing and have not surveyed the area. All of this means that the ford data in OSM can be of very poor quality.
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I’m thinking there are a large number of NHD ephemeral streams, that are listed as intermittent streams in OSM, that should be retagged as natural=gully.
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