[Tagging] Off Topic: alignment point help

Warin 61sundowner at gmail.com
Thu Jun 11 10:07:18 UTC 2015

On 11/06/2015 6:14 PM, johnw wrote:
>> On Jun 11, 2015, at 4:49 PM, Martin Koppenhoefer 
>> <dieterdreist at gmail.com <mailto:dieterdreist at gmail.com>> wrote:
>> offsets are an approximation to reduce the inherent problems of some 
>> aerial layers, they won't solve problems like distortions. JOSM isn't 
>> more precise to find a "proper offset" than any other tool, I suggest 
>> you simply move the layer till it visually seems ok. Unless you do 
>> high precision measurements in the field you won't know for sure what 
>> is "right" and what is "wrong", or in other words: more or less 
>> accurate. IMHO, relative precision (eg alignment, angles, straight vs 
>> curves etc) is more important than positional precision.
> I know the precision isn’t so important, but I want everything to be 
> the same relative location. The relative position is very important to 
> me. I know distortion can skew that, for hills and the like.
> I was also under the impression there was a plugin for JSOM that 
> offered automatic imagery offset correction, something which I don’t 
> have access to in iD

I think that JOSM offset is simply from someone sending in their offset. 
I don't trust it.

If you want to pick an OSM node/way to align to, I'd chose one that is 
close to the imagery alignment and has a  tag with source:location= 
gps/survey .. and preferably one that has not been moved since that tag 
was added.
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