[Qgis-user] Offline background map for large regions

[abru345 at gmx.de]

Hi Patrick,

thank you for your kind reply.

My goal is  to become completely offline. It does not have to be the
most recent map, but it should be visible on the screen all the time.
E.g., friends of mine live at the countryside and if you want to make a
call at their place with your cellphone, you have to climb on a high
stand they prepared especially for this purpose.

About my hardware, it seems to have enouh RAM, as about 80% is free when
I import the file. Also, the system runs on a SSD and I have no IOwait
at all. The bottleneck seems to be the CPU. It uses only 1 core which
runs at 100% for hours. Until now I was not able to find out what's
going on then. The smallest map I cound find was the one from
Luxembourg, and even then...

But I will try to switch to the most recent QGIS version by using
flatpak. Maybe that changes something.

Andreas



Am 10.07.22 um 16:31 schrieb Patrick Dunford via Qgis-user:
> When it comes to a website, generally, a good way of getting background
> maps (rasters) is XYZ tiles or similar with the different zoom levels.
> Each higher zoom level doubles the amount of tiles needed, so the way to
> avoid too many tiles taking up too much space is to reduce the number of
> zoom levels needed to some realistic amount. The tiles are generally all
> the same size 256x256 pixels and it works very well in a web client over
> all different speeds of connection. You start at the lowest level and
> then zoom in to the next level and so on. This is how it is possible to
> do it over slow small devices such as phones, only downloading the tiles
> that actually need to be displayed at that point.
>
> I am not sure if this is what you are referring to or something that
> actually loads in the Qgis canvas, in which case the above might not be
> relevant. But I have worked with many raster tiles loaded off the hard
> disk as backgrounds and generally there has not been a speed issue for
> them. However if you don't have enough RAM, this could create a problem.
> If you expect to use a lot of swap then buy a large SSD and set this up
> as you swap partition, since it will perform much better than a regular
> hard disk.
>
> Also look at what resolution the downloaded imagery is, you may not need
> more than 1 metre resolution depending on how much you need to zoom in,
> so that you could be able to reduce the filesizes quote a lot.
>