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.
I suppose, at the time it was written, this was the most straightforward
way to get it done. It's not necessarily the best...
Alternatively, you could save the offset in meters, but I'm not sure if
there is a direct way to convert it back into eastings/northings
difference. (We have only latlon2eastnorth and eastnorth2latlon formulas
implemented.)
If the values are read from a database, it should be no problem to make
this zoom level dependent. But the user interface for manual
per-zoomlevel adjustment could be a challenge... Is it worth the effort?
Often you will be only interested in the highest zoom level and it
shouldn't be too hard for the imagery provider to align the images of
different resolution relative to each other.
Regards, Sebastian
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