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I want to add buildings in my small village to OSM. Bing images fitting very good to the drawn streets. Whats the appropriate way for adding buildings? Going to every corner of a building with my GPS (may be more accurate but not all corners are accessible) or redraw it by means of the Bing image (more time effective?) Thanks for your help. Stefan |
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You could set up some temporary Bing reference points using your GPS. Find a clear sharp angle such as a low wall junction, corner of a paved area,or something like a centre of roundabout. It has to be visible on Bing and not changed recently. As long as there is a good uninterupted 360 degree view of the sky, take a number of readings of each point. Plot these as nodes with a tag of Ref Point. Adjust your Bing image to these ref points, ( you may have to even out the adjustment depending on the flatness or hilliness of your village,)You can then plot your buildings from Bing. Then go out and ground check for hidden items and anything you are not sure about from Bing such as hedge/fence/wall. 3
Indeed. Bing and GPS is not an either/or, they can work together that way, and should do so whenever possible. GPS is great for roads, but will not be good enough close to most buildings. Bing is great provided 1) it has been verified on-site to be up to date, and 2) it has been calibrated locally using good gps data.
(13 Dec '11, 10:46)
Vincent de P... ♦
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If you have enough gps traces to confirm the alignment of the bing and the bing is of good quality in your area then I would use bing. have a look at past questions by doing a search for questions such as this one http://help.openstreetmap.org/questions/6385/alignment-of-track-vs-background-imagery one way to get some good fixes with your GPS is to stay still for a while or to sit on park bench, which I can see on bing in my area, the trace will record a blob of points,an average,so do this at a few locations and it should give a good fix. here's how to draw buildings http://wiki.openstreetmap.org/wiki/Roof_modelling#Drawing_of_building_outlines_based_on_low_resolution_aerial_images |
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If you have good Bing images then it can be faster. However you need to survey the area to get the best result. Many features are hard to tell from the satelite images but easy from the ground. If you are going to an are with a lot of steel and concreete building you often get the urban canyon effect which limits the accuracy of the gps. |
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The HDOP of GPS near walls tends to be high; you're best off setting a reference landmark on the GPS, then tracing the outline on the aerial. |
