Well I finally got around trying out the overview map. For what it is
supposed to do, it works for me now.
However I would really like to have multiple levels in the overview map.
So for a start, the overview file (to be present in future could contain
in the first line, a levels definition, just like what is currently used
in the options file for the normal maps).
As for objects disappearing in between. Garmin does just that in the
overview map of CN maps. There you have the main important train
connections in Europe in the highest level of the overview map. They are
missing in the lowest resolution of the normal maps however, to reappear
in the next map level.
The reason could be, that displaying the overview map is very CPU/HDD
effective, while the more is shown on the lowest normal resolution of
the map, the slower the device/mapsource/basecamp gets.
Still I would really love to have resolutions 10,12,14,16 all with map
data in the overview map. 16 being empty in the normal maps. And from
resolution 17 or 18 normal maps with data.
I suppose this is possible with
Sample:
line:0x1e,level=1
However I think it would be much better to have the overview map created
directly from the osm base material, and not from the .img. Creating
from .img could be an option too, but it simply only offers limited options.
Image you have in your map:
highway=motorway & network
<http://wiki.openstreetmap.org/wiki/Key:network>=e-road
<http://wiki.openstreetmap.org/w/index.php?title=Tag:network%3De-road&action=edit&redlink=1>
[resolution 14-14 0x01 continue]
highway=motorway [resolution 16-18 0x01 continue]
So clearly the e-road trunk is much more important, while also being of
type 0x03. If the aim is now to have resolution 16 empty in the map,
while showing content in the overview map, this is not possible anymore
using the current approach of reading the finished .img files.
It would be much easier if inside the options file we have:
levels = 0:24, 1:22, 2:21, 3:20, 4:19, 5:18
levels_overview_map = 0:16, 1:14, 2:12, 3:10
And if there is a need to create subsequent overview maps, than an
existing overview map could be copied and information added based on the
current algo (copy in data from last used resolution, if resolution
matches the levels_overview_map pramater. So i.e. copy in map content of
resolution 16, but don't copy in data from resolution 18 if resolution
16 is empty)
On 11.04.2013 09:38, GerdP wrote:
WanMil wrote
Yes, and I think it makes sense to do that. If you add something to the
overview map which
is not shown in the next level, you will see that the boundary lines
disappear in Basecamp when you zoom in
(using full map data, not basemap only).
You can implement styles where this happens in the normal map.
boundary=administrative & admin_level<3 [0x1e resolution 16-18 continue]
boundary=administrative & admin_level<3 [0x1e resolution 22]
The boundary will disappear in resolution 19 to 21.
Don't know if that makes sense but it is possible. So I don't see a
reason why this shouldn't be possible for the overview map too.
Well, I can change the format of the config file so that one can specify
the level or resolution which should be used to read the data from.
This would be an optional parm, with the default being level 0 (resolution
24)
Sample:
line:0x1e,level=1
or
line:0x1e,resolution=22
Open question:
Should I also add support for multiple levels in the overview map?
This would result in something like this:
line:type=0x1e,from-resolution=22,to-resolution=13
with the meaning:
Read the img files, collect all lines with type 0x1e on map resolution 22
and place them in the overview map on resolution 13.
The defaults would remain as they are: read only the lowest resolution,
place everything on level 14.
Gerd
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keep on biking and discovering new trails
Felix
openmtbmap.org & www.velomap.org
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