[Qgis-user] offline googlemaps (or the like) images

[Pierre Chevalier Géologue]

(@#! I forgot *again* to "reply *all*" on this list!...)

Vincent Schut claviota:
 > Hi,
 > I'm going to do some fieldwork in some pretty remote places,

Sounds familiar! ;)


 > and I'd like to use qgis (combined with the qgismapper plugin to match
 > my gps and photo's). What I'd really like to have, is some highres
 > background imagery, like the satellite layer from googlemaps. Anyone
 > knows of a way/tool to fetch a predifined area of this (or another
 > service which provides highres background imagery) as a georeferenced
 > image, so I can use it offline as a background layer while
 > gps-wardriving the swamps of Borneo?

Google layers extension is very good at this.

1/ open qgis
2/ get the google layers plugin
3/ choose projection = google mercator (EPSG: 900913)
4/ get some data where your area is located (couple of roads, rivers,
whatever... just so that you know where you are)
5/ menu Extension / Google layers / Settings
6/ dialog box: choose "satellite" option
7/ go where you wish
8/ menu Extension / Google layers / Google layers
9/ miracle: satellite image from google maps is right there

If you zoom close enough, you'll get a decent image, georeferenced, etc.

The images end up somewhere in a temporary directory. On my GNU/Linux
Debian machine, they arrive in /tmp/google_layers/ with some fancy names.

What I do is, after I downloaded the images I want, is merge them into a
unique file. For instance, this is the command I used last time I did
this task:

pierre at duran:/tmp/google_layers$ gdal_merge.py -o
google-satellite-cote_ivoire_sl.tiff
google-satellite-z8-11-24092010_2203221285358602.jpg
google-satellite-z8-10-24092010_2203221285358602.jpg
google-satellite-z8-7-24092010_2203221285358602.jpg
google-satellite-z8-8-24092010_2203221285358602.jpg
google-satellite-z8-9-24092010_2203221285358602.jpg
google-satellite-z8-12-24092010_2203221285358602.jpg
google-satellite-z8-13-24092010_2203221285358602.jpg
google-satellite-z8-1-24092010_2203221285358602.jpg
google-satellite-z8-2-24092010_2203221285358602.jpg
google-satellite-z8-3-24092010_2203221285358602.jpg
google-satellite-z8-14-24092010_2203221285358602.jpg
google-satellite-z8-15-24092010_2203221285358602.jpg
google-satellite-z8-4-24092010_2203221285358602.jpg
google-satellite-z8-5-24092010_2203221285358602.jpg
google-satellite-z8-6-24092010_2203221285358602.jpg


As you can guess, this was in Ivory Coast.


Before, I used to use viking to download images, then export them, and
georeference the final image. But with this extension, it is more
convenient, I find.

Hope it helps.

A+
Pierre
-- 
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Pierre Chevalier Géologue EI
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