Google Sat - Some tiles can't be downloaded (error 404)

[arekkusu]

FoxtrotGPS v. 1.0.1 from Oneiric deb package running on Xubuntu 11.04

Some tiles don't get downloaded for google sat. I did not manage to download any tile on the 100km or more scale. When checking the program error message, it appears that the google server respond with an error 404. When zooming further in (20km scale) I am however able to view the image, although the odd one also return a 404 error.

I am using the default setting for google sat: "http://khm.google.com/kh/v=53&x=%d&y=%d&z=%d" + "xyz instead of zxy" checked.

Example of tile that failed:

**Totally zoomed out (could not download any tile)**

TILE DL PROBLEM: The requested URL returned error: 404
http://khm.google.com/kh/v=53&x=5&y=2&z=3|/home/alexandre/Maps/googlesat/3/5/2.png|/home/alexandre/Maps/googlesat/3/5/

**100km (could not download any tile)**

TILE DL PROBLEM: The requested URL returned error: 404
http://khm.google.com/kh/v=53&x=149&y=90&z=8|/home/alexandre/Maps/googlesat/8/149/90.png|/home/alexandre/Maps/googlesat/8/149/

**20km (Most tiles arround download without problem)**

TILE DL PROBLEM: The requested URL returned error: 404
http://khm.google.com/kh/v=53&x=256&y=164&z=9|/home/alexandre/Maps/googlesat/9/256/164.png|/home/alexandre/Maps/googlesat/9/256/

In lower zoom level tiles usually download but the odd one that's get downloaded (error 404)

[Joshua Judson Rosen (rozzin)]

Checking osm-gps-map, which should face the same issues as we do with tile-providers, I see that John recently added a google-fix: https://github.com/nzjrs/osm-gps-map/commit/d1e6825c5be58eb9ae96abe8e6b6d6e4e5ecefbf

The `v=...' parameter in Google satellite-imagery URLs is presumably to peg a version of the tile-database; we're currently using "v=53", and John's fix in osm-gps-map was to raise that number to 89 (which appears to work, as far as I can tell). What we're seeing with v=53 is presumably just a result of Google `aging out' their older imagery-databases.

It looks like the current number (which is in use on <http://maps.google.com/>) is 92, so I guess we might as well use that.

[Joshua Judson Rosen (rozzin)]

Of course, this is an easy fix in init.c..., but it handles only the cases where FoxtrotGPS is still using only its default set of maps--if the user has added any new maps, then all of the default map-definitions have been copied into GConf, and the problem will persist there even after the C code is fixed.

For the time being, maybe it's sufficient to just document this in the NEWS file (e.g.: `you may need to edit your Google Sat definition and change "v=53" to "v=92"')?

[Joshua Judson Rosen (rozzin)]

For the time being, I'm considering describing this in the NEWS file thusly:

    * The default Google Sat URL has been updated to accomodate Google's
      removal of older imagery from their database. Note that existing
      users may have to edit their `Google Sat' Map settings and manually
      change "v=53" in the URL to "v=92".

[Joshua Judson Rosen (rozzin)]

I've committed a code-fix to the trunk at revno:167, revid:<email address hidden> (along wiith notices about how existing users may still need to tweak things manually).

Also, cf. bug #858591, which addresses the problem mentioned in comment #2.