OpenStreetMap
It happened to me that the GeoEye for Haiti are moving back and forth in Potlatch. Sometimes they are a little bit more to the left and then a little bit more to the right. It is quite a annoying and after you have moved some streets the images are again at a different place. E.g. the presidential palace which I have moved has now shifted again (not due to the earthquake but due to the movement of the GeoEye images). What is happening?
讨论
SK53 于 2010年01月16日 23:49 的评论
Please dont move mapped objects on the basis of imagery which may have residual errors from the rectification process. Instead move the imagery (shift-drag in Potlatch, WMS icon in JOSM) to correspond with already mapped objects: at the very least they will retain their correct topology and remain relatively accurate.
Continual movement of map data will only degrade accuracy: particularly if the most accurate data (imported pre-quake) are moved to align with less accurately calibrated images. In the absence of control data, such as GPS tracks, there are limits to the accuracy of rectification. Furthermore we now have a huge range of different sources each with its own imperfections, and none have been corrected with on-the-ground data.
ALE! 于 2010年01月17日 00:37 的评论
Thanks for the clarification.
ALE! 于 2010年01月17日 00:38 的评论
Sorry I forgot something: But why does the GeoEye images move? Are they not fixed?
ALE! 于 2010年01月17日 00:49 的评论
And one more thing: shift-drag does not work in Potlatch. At least I do not know how.
ALE! 于 2010年01月17日 10:20 的评论
As nobody answered I found it out myself after some while: It is space + drag. But it still does explain why the background moves from time to time from the left to right and back.
Andy Allan 于 2010年01月18日 11:06 的评论
It might be the guys who are serving the imagery improving their rectification.