[OSM-talk] [OSM-newbies] Tracing and offset error

[Martin Koppenhoefer]

2012/12/8 Michael S <michael at elfu.de>:
>>In the absence of immediate local presence, is tracing acceptable and not
>> wasted effort.
>
> Personally I only do aerial image mapping to a limited extent because I fear
> that I will map wrong objects (e.g. nonexisting buildings, roads) because of
> outdated bing images. I feel much more comfortable to do bing mapping when I
> also do know the surrounding by own survey.
> However, I would follow a pragmatic approach: E.g. If there is no railway at
> all in the map, and you think that it is likely that the railway is still
> there I would go for remote mapping.


+1, in the absence of local presence it is IMHO better to trace (what
you think you can identify and where you suspect that the imagery is
not too old) something if you feel like instead of leaving the map
completely empty. There is obviously a huge difference between mapping
in areas with very few mappers like in parts of Africa, and tracing in
an area like Germany with lots of mappers.


> Offset Problem:
> Maybe you could compare objects already being mapped on a large scale (
> larger towns ) and only do large scale mapping  like major roads, but no
> micro mapping like lake boundaries on a 50 m scale without having better
> offset information.


You can always move a lake later if you see that it was offset.
Although this is not desirable it might be the only way to do tracing
if there are no GPS traces available to align the imagery.

cheers,
Martin