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?
Discussion
Comment from SK53 on 16 ஜனவரி 2010, 23:49
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.
Comment from ALE! on 17 ஜனவரி 2010, 00:37
Thanks for the clarification.
Comment from ALE! on 17 ஜனவரி 2010, 00:38
Sorry I forgot something: But why does the GeoEye images move? Are they not fixed?
Comment from ALE! on 17 ஜனவரி 2010, 00:49
And one more thing: shift-drag does not work in Potlatch. At least I do not know how.
Comment from ALE! on 17 ஜனவரி 2010, 10:20
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.
Comment from Andy Allan on 18 ஜனவரி 2010, 11:06
It might be the guys who are serving the imagery improving their rectification.