The watercourse data in Southern Alberta, Canada (as well as some other parts of the country) is really inaccurate. Hundreds of km's of watercourses are not showing in OSM. This data is available in Geogratis - a data set produced by the federal Government of Canada and is free to use (as in not copyrighted). (I know this is important, but my question is more about the technical side of things - let's not start a copyright debate - I am sure the existing set came from them too, but it's old and inaccurate).

I would like to use the dataset to improve OSM. How do I do it? I can download the data in a vector format (shapefile) - one tile at a time... then what do I do? How do I import the whole shapefile (covers about 36km x 27km area) into OSM? Uploading each stream in GPX and Re-tracing it is way too laborious and will produce errors (= not an option). Is there a way to do this in JOSM? How? Is there a procedure that's written out for this?

asked 14 Dec '17, 09:04

pbcnp's gravatar image

pbcnp
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accept rate: 0%


The Canada data in OSM suffers from a great many badly done imports. Often, data was already bad and outdated at the time it was imported. It is therefore very important that you first check that the data you wish to import is indeed an improvement.

With waterways data especially, there's a number of potential pitfalls about their classification; you don't want to end up with ditches that are dry most of the time prominently shown on zoom 10.

When importing data, you will be expected to "conflate" it with existing data, i.e. make sure you don't create duplicate copies of things; you cannot simply delete everything that's there and replace it because that might kill someone's diligent tracing from aerial imagery of a river and replace it with a lower quality version from your import. Also, the data you are importing might "interact" with other data that is there (and might have been imported from a different source). Imagine a forest area that ends at the riverbank; you wouldn't want your new river data to meander in and out out of the existing forest, or maybe even cross into an existing building or so. Also, you will be expected to check if the edges of your shapefiles actually match up, something that has been an issue with previous imports in Canada. There is much more to a successful import than converting a shape file and uploading it. It will be laborious, and if this is "not an option" for you, then you cannot import the data.

What you can do is try and distribute the labour onto many shoulders - you could help prepare the data for import, and then seek people who help with the conflation. Ideally, these people would be locals to the area being imported and could bring local knowledge to the table as well.

It would be best if you asked your question again on the imports mailing list where you're likely to find people who have done similar work before.

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answered 14 Dec '17, 09:29

Frederik%20Ramm's gravatar image

Frederik Ramm ♦
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accept rate: 24%

Thanks for your answer! To be clear, I know it will be laborious, but re-tracing each stream would take the work to a whole new level (= two orders of magnitude more time? That's the part I am not excited about). I like the idea of only adding to the OSM data currently there - I don't want to undo anybody's work. I am fine with just doing the local area I know, and only adding tails of creeks that are currently not in OSM. Then I could also re-align them with aerial imagery where possible. Thanks for the suggestions.

(14 Dec '17, 17:20) pbcnp

pbcnp, don’t forget that IMHO OSM & GPS trails or tracks are congruent, building streams inside a forest without an observation is hardly reliable. Start or stick to the local area and take a hike. And don’t forget to add the local or known names as well. I once walked along Carrot Creek from Lake Minnewanka but looking at it here, https://www.openstreetmap.org/#map=17/51.16642/-115.39166 its a bit of a strange mess. (import without survey?) But named, yes. So be carefull.

(17 Dec '17, 15:13) Hendrikklaas
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question asked: 14 Dec '17, 09:04

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last updated: 17 Dec '17, 15:13

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