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Hi to all I'm a newby round these parts so be gentle if the answers are obvious. After editing a section of road using Bing as the source positioning data, and inputing new or corrected traffic flow data and other relevent details then finally I save the edit. When I return to continue from the last saved section, maybe a day later, I find the previously correctly position node has moved when compared to the Bing position. Why does this happen, and is there a way to stop it ???? BillyWizz |
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How far have the nodes apparently moved? I have noticed that the alignment of the Bing images can vary a little depending on the zoom level. Look at the cycle track in the centre of the map at http://www.openstreetmap.org/?lat=50.857992&lon=-1.187635&zoom=18&layers=M using Potlatch 2, and watch how the alignment moves by two or three metres as you zoom in. Under ideal conditions, a modern hand-held GPS can be about that accurate, and the average of several tracks taken at different times can be better. By 'ideal conditions' I mean that there are no obstructions (trees or tall buildings) in the immediate vicinity, and the GPS has had a good satellite fix for a minute or so, to allow it to settle. |
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In answer to the "how do you align the Bing imagery in Potlatch" part of the question, have a look at the answers to this previous question - they should help. |
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Thank you to everybody that took time to responded to my question. I have followed up and researched your points and sugestions. I now have a better understanding of what is happening to my edits and have more confidence to carry on and just do do more. I now understand and have observed that Bing has more than one image at different magnification levels which make it appear that nodes move. I can find no evidence of anybody modifying my work. I also understsnd the effect of the natural error within GPS which explains why my self imposed "Quest" for absolute accuracy is not essential. Thanks again for all your help. Bye |
Have you made sure that your Bing imagery is properly aligned so you are not entering a lot of apparently misaligned data into the OSM database that someone else is trying to correct?
Does the history of your entered objects tell you if it's a specific user that is modifying your edits over and over again?
I assumed the Bing imagery is auto aligned. Is this not the case? if not how do you align it? None of the data re traffic flow data etc has been changed and my work does not look as though anybody else has edited it.
You also have two Bing images, one from 2011 the other earlier. Both are different alignments. When zooming in from one image to the other a particular node will seem to move. I don't use Potlatch so can't say how realign the image but a search of past questions should gather some information.
One thing that might be useful would be if you could post a link to the area that you're talking about. That way we can have a look at it, and have a look at any underlying GPS traces, and hazard a guess about any systematic offset in the Bing imagery. We'd also then know whether the area was hilly or not, which can be relevant.
There's a "permalink" option in the bottom-right-hand corner of the OSM map.