Re: [ gpsdrive ] Goole maps projection/offset

["Joerg Ostertag (gpsdrive Munich/Germany)" <gpsdrive@ostertag.name>]

> >>> now have 3 Projections implemented in gpsdrive: the old map_ top_ and
> >>
> >> the new
> >>
> >>> googlesat projection.
> >>
> >> We have "googlesat projection" implemented in gpsdrive? Does this
> >> mean, we can use Google-Maps-pictures at last?
> >
> > gpsfetchmap.pl -a 1 -w MyHome --mapserver=googlesat
>
> To come back to this old topic (sorry):
> This method doesn't work for me. It does load the images from the
> server but they are way off the real position.
> How do I track if it's a glitch in the fetch-and-download or in the
> gpsdrive-part?

I think they are both (gpsfetchmap and gpsdrive) inaccurate/wrong/incomplete. 

If you can work with a resolution of 1280x1024 or higher it would make things 
easier, since you can see the complete image on the screen and you can more 
easily see which deviation is comming from which of the factors described in 
the following lines.

The second thing is to use 
 gpsfetchmap.pl -d 
This way you get markers into the stitched images. These tell you where 
gpsfetchmap.pl thinks the corners of the images are.

Third thing would be to always look into the middle of the displayed (in 
gpsdrive) map to see if this center point has an  offset and how much this 
offset is. This only works if gpsdrive displays the complete image and not 
only part of the jpg. If you find the offset of the center point of the image 
inside the jpg. You might be able to correct the formula inside 
gpsfetchmap.pl which writes the center into the map_koord.txt.

The next step then could be to find which projection the googlesat-images are 
using. You can then adjust the projection routine inside gpsdrive to reflect 
this.

If you got these all sorted, your next step would be to find the right 
gpsdrive-zoom scales for the appropriate google zoom scales. 
Well i think this could do it.

It will be a lot of testing, measuring and calculating. But if you have any 
progress in this step please tell us.

-

Joerg

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