[OSM-talk] Deleting data

Christoph Hormann chris_hormann at gmx.de
Sat Oct 19 10:58:30 UTC 2013

On Saturday 19 October 2013, Frederik Ramm wrote:
> I think that is the core of the problem. For many, the visual power
> of the aerial imagery is so strong that any data not matching the
> imagery is deemed wrong.

It seems to me instructions for beginners concerning mapping based on 
imagery could much better cover this matter.  While the problem of 
position offset is frequently mentioned and illustrated in tutorials 
there is usually at most a simple 'be aware that things might have 
changed since the time the image was taken' concerning actual 
interpretation of the images.  In my experience people for example 
usually only start to realize the problem of outdated images after 
actually seeing how things change in imagery over time (which they do 
not by looking at Bing etc. except if they consciously witness an image 

Interpreting aerial/satellite images is a difficult task and people who 
do this professionally usually spend a lot of time learning how to do 
it.  It is not reasonable to assume that for the average OSM mapper 
this is so self evident that no explanation is necessary.  None the 
less editors mostly show the images in the background and the mapper is 
essentially left alone with what to do with it.  I think it is to be 
expected that there are quite a few mappers who then simply try to 
adjust the data to match what they see in the images by either 
changing, deleting or adding elements.

Christoph Hormann

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