breakthrough

[hamish_b]

Hi folks,

with some hints from Tobias Sauerwein (OSGeo/Google Summer of Code student who just added webtile support for uDig GIS) I think we've finally cracked the OSM scale-varies-with-latitude problem.

This means that tiles made with gpsdrive_mapnik_gentiles actually
seem to line up correctly! I'll adjust map_download.c for OSM@home
and gpsfetchmap.pl ASAP. Previously the scale was badly wrong.


Please move away your old .gpsdrive/maps/mapnik/ maps + map_koord.txt,
generate new ones with gpsdrive_mapnik_gentiles.py, dig out your GPX
tracks for overlays, and test test test!


AFAIK everything is using the Google Mercator projection now, the
old OSM merc projection is dead? (I am confused with the -m's)
There may still be some slight distortion near the corners, and
at country/global scales it will probably be bad, but those are
limitations of the projection and nothing much we can do about it.

Anyway a coordinate from a maps.google.com URL Link now lines up
with street maps, so I think it's all the right way around.


glad,
Hamish
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[hamish_b]

Hamish:
> with some hints from Tobias Sauerwein (OSGeo/Google Summer
> of Code student who just added webtile support for uDig GIS)
> I think we've finally cracked the OSM
> scale-varies-with-latitude problem.
>
> This means that tiles made with gpsdrive_mapnik_gentiles
> actually seem to line up correctly! I'll adjust map_download.c
> for OSM@home and gpsfetchmap.pl ASAP. Previously the scale
> was badly wrong.

This is now done.

> Please move away your old .gpsdrive/maps/mapnik/ maps +
> map_koord.txt, generate new ones with
> gpsdrive_mapnik_gentiles.py, dig out your GPX tracks for
> overlays, and test test test!
>
> AFAIK everything is using the Google Mercator projection
> now, the old OSM merc projection is dead? (I am confused
> with the -m's) There may still be some slight distortion near
> the corners, and at country/global scales it will probably be
> bad, but those are limitations of the projection and nothing
> much we can do about it.
>
> Anyway a coordinate from a maps.google.com URL Link now
> lines up with street maps, so I think it's all the right way
> around.

happy mapping,
Hamish



     

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