Changeset: 54101660
(no comment)
Closed by SverigeFan
Tags
created_by | JOSM/1.5 (13053 de) |
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source | DigitalGlobe Premium aerials, shifted from Strava heatmaps |
Discussion
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Comment from Gazer75
Did you forget to reset imagery offset? The entire riverbank of Tana river is misplaced now.
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Comment from SverigeFan
The changeset is some month old and looks good for me if I view it on DigitalGlobe aerials: Could you specify which reference you use to judge the data are incorrect ? I think I didn't forget to reset an offset but have used GPS tracks from Strava (users) , which were available für download at high resolution / quality at that time, besides some own tracks from the summers of 2015 and 2017 to add offsets to DigitalGlobe aerials - different offsets since, although mostly better than Bing aerials, DigitalGlobe aerials aren't perfectly reprojected / orthorectified at all places. I then did draw on these shifted aerials: I'm quite sure that using the Strava data (many users, not only a single track) as a reference is an improvement of the OSM-data to simply drawing on aerials.
Since Strave stopped to provide high resolution data (those available now are much troo inaccurate to improve DigitalGlobe Premium aerials, because of securitty reasons, I cannot reproduce this now
Greetings, Rolf
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Comment from Gazer75
https://www.openstreetmap.org/changeset/54101660#map=14/70.2017/28.1963
If the riverbank matches your DG imagery then there is something very wrong at your end.
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Comment from Gazer75
Any roads imported that use "Kartverket" as source will be a perfect source to align imagery to. This road data is the official data for Norway.
You even edited the riverbank after the construction of the new bridge at Tana Bru was added making it appear in the river. That should have made you realize something was off :)
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Comment from Gazer75
The DG imagery for area around Tana Bru is only off by about 5-10m at most.
Forgot to mention... at least now there should be several options to pick Kartverket data in JOSM when editing in Norway. This should help you align any imagery.
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Comment from SverigeFan
Indeed, that is very wrong,
I was looking near Tanamunningen where the first obkjects from that changeset are laying.
Now I will see how to fix *that*
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Comment from Gazer75
If you wait a few weeks we might have a server to access official rectified Norwegian imagery that will rarely have an offset of more than 1m. We have the permission to use the imagery, but not permission to use a cache server yet.
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Comment from Gazer75
Adjusted imagery from DG or Bing are only valid for like 100m or so in many cases. You have to keep adjusting to known good spots.
Not many of the active mappers in Norway use them for anything more than basic info because of the bad alignment. -
Comment from SverigeFan
Well - for now I made a - maybe rough - fix by hand. Thank you for your hint on the mistake. My first reply of course was irrelevant, since I was disussion imagery offset which wasn't the problem at all here, where someone, I fear me, had shifted the Tana riverbanks multipolygon quite a lot while trying to optimize it.
Nevertheless it would be kind if you could advise me about the server with the official norwegian imagery when it's operational. Being in Sweden, Finland and/or Norway regularly for my summer holidays, I prepare the tours by mapping interesting regions or spots in OSM and add tracks and other info after the trip - for me thats about half the fun of traveling. Since I know about the problems and limitations of orthorectifying aerials especially in steep terrainas I wrote before I was always trying to improve accuracy by using GPS-data from different sources. Having really precise aerials would make mapping much easier. While I can read Norwegian texts with some effort, I don't have the time to follow the open data - initiatives from Kartverket in Detail. So a link or two would be helpful.
Thanks in advance and again for pointing me on that obvious misttake.
Greetings, Rolf
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Comment from Gazer75
Keep an eye on the imagery list in JOSM when mapping. It will probably appear there once a host has been found.
For now you can view the imagery at norgeibilder.no and drool :) There is a small globe icon in top right corner on the page that will give you English language.
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