[Tagging] Off Topic: alignment point help

johnw johnw at mac.com
Thu Jun 11 08:14:20 UTC 2015

> On Jun 11, 2015, at 4:49 PM, Martin Koppenhoefer <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 also deal with places where the tracings/imports are 2-5 years old, nowhere near aligned to the imagery, has several 20m shifts every few KM, so who knows what is right, and the trunk roads/motorways have more recent edits of several different users aligning to past imagery with and without an offset, so there is no place whatsoever where I can choose a dominant alignment. even inside Narita Airport there is a 5m or so diffference betweent the buildings and the runway mapping. and the taxiway mapping is old. So I don’t know what to trust
And I don’t want to make one up because...

Mappers using JSOM to come in and start moving all major roads over 1 lane width and leave all the residential and alleys alone - effectively ruining their relative positions and distorting all the intersections. This happened *all the time* until I started requesting an alignment point from JSOM users.

I sometime micromap very tiny places, which means the space between the roads, and when mapping towns/areas I include every single possible road (alleyways and residental) - and having someone come through and move only the trunk road over 2 meters throughout 20 sq km of residential roads I just meticulously aligned is a PITA. It is impossible for me to select and shift 100,000 points 2 meters over. and now I’m starting to map landuse polygons and buildings (correcting horribly sloppy work) - but if I lay down all of these objects, someone coming in and shifting the road 2m Southeast makes everything look bad. 

If I have someone using JSOM align a polygon that is easy for me to align my map to each time I start iD, it is much less likely to occur. 

So here I am, hat in hand, asking for that aligned point. 

http://www.openstreetmap.org/edit#map=19/35.74840/140.38510 <http://www.openstreetmap.org/edit#map=19/35.74840/140.38510>

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