On Thu, Dec 16, 2010 at 19:28, Sebastian Klein <basti...@googlemail.com>wrote:
> Eugene Alvin Villar wrote:
>
>> On Thu, Dec 16, 2010 at 10:35 PM, Chris Browet <c...@semperpax.com>
>> wrote:
>>
>>> On Thu, Dec 16, 2010 at 15:22, Eugene Alvin Villar <sea...@gmail.com>
>>> wrote:
>>>
>>>> Hmmm, is there a way to enter the offset into a form instead of
>>>> dragging? And could this offsetting be compatible with JOSM? It would
>>>> be if multiple contributors can share offset values even if they use
>>>> JOSM or Merkaartor. :-)
>>>>
>>>> No form, yet.
>>> And what would be the JOSM-compatible offset values?
>>> - Chris -
>>>
>>
>> I haven't personally used the imagery offset feature of JOSM, but a
>> fellow mapper told our mailing list that the offset for one particular
>> place is in eastings and northings, whatever that means:
>>
>> Easting: -5.00000E-7
>> Northing: -5.00000E-7
>>
>> It seems that this is an absolute value setting irrespective of zoom
>> level and I am not sure if these are based on a projection or not.
>>
>
> The offset in JOSM is related to a particular projection. The dx and dy
> ("easting and northing") are added to the projected coordinates x and y.
>
In Merkaartor, the underlying displacement is in lat/lon, which is not
"right" but projection-independent. JOSM'way is right IMHO, but difficult to
implement in Merkaartor which supports basically any projection.
Frankly, the only reason I implemented it is to be able to use high-zoom
Bing which is shamelessly wrong at some places.
I don't see this as having any "geographic" value, just because, in most
place, we don't have multiple-crossed reference points to align to.
Furthermore, I assume the displacements are different from place to place
so, IMHO, visual alignment is as good as anything else...
Unless Microsoft has some DB with known displacement, of course, but I doubt
it as disabling the "side-view" on Bing shows exactly the same errors...
What would be great is to have, publicize and use a number of reliable
points, tagged in a specific way. I know that france have a number of those
that but I don't know if it is true worldwide...
- Chris -
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