[mkgmap-dev] new branch low-res-opt to test improvements for filters

Wed May 5 11:47:02 BST 2021

at 300m there is no difference at all. Actually the patch will help you to
set lower DP level for 300m (that is resolution 23 in Basecamp) while
giving higher DP values for higher resolution. That came because for
contourlines it needs very low DP value for resolution 23, while if you
keep that low DP value for higher resolution, it makes the map unusable on
device and even slow in Basecamp.
resolution 22=700m
resolution 21=1.5km
resolution 20=3km
resolution 19=7km
resolution 18=15km (if you use high DP filter - this is the first
resolution where the simplification will mean the route is visually quite
different from the underlying road, but still very easy to know which road
it belongs to(
resolution 17=20km
resolution 16=50km
.....

with default style:

levels = 0:24, 1:22, 2:20, 3:18
overview-levels = 4:17, 5:16, 6:15, 7:14, 8:12

So 17 will never  actually be shown on your device. That's why I mean -
even giving high DP filter values (though in the branch because of less zig
zag you achieve the same size with lower DP values!) will only be a bit out
of place if you autoroute Berlin to Madrid.
Actually the basemap of most newer Garmin devices has the following
resolutions:
level 0=17
level 1=15
level 2=13
level 3=12
level 4=11
level 5=10
level 6=9

it's too bad that there is no basemap starting with level 0=18
- I feel that would give better performance. resolution 18 is already quite
slow to scroll around if you have topographic maps no matter how much you
reduce the data - because it will need to read in quite a few tiles each
time. But OSM data is not very suitable to create a new worldwide basemap.
The values that I mentioned DO of 8-10 actually seem to be lower or similar
to what Garmin is using. The default of 2.6 is crazy detailled in
comparison.

On Wed, 5 May 2021 at 17:23, Thomas Morgenstern <webmaster at img2ms.de> wrote:

> before  misanderstandings arise, maybee you can post here screenshot's ? by
> carrouting I mostly use 300 m details in cities. By using this
> resolution, the map should very accurat, not simplified. By very long
> travels 3 km details. Using 3 km, the map can bee simplified. I don't
> know, how this is correspondending to Levels/resolution. Can you post
> screenshot's #old style# vs #simplified style' ?.
>
> thomas
>
>
> [quote]
> Hi Karl,
> But even then you will never use the overview map.
>
> What resolution are you actually using on your device if routing on a
> highway? I guess 19 or 20...
> The thing is simply with high DP filter value that you can see the highway
> pretty straight, but as the route itself is not simplifed that much in
> Basecamp. The route will not be 1:1 visually of the map. But still very
> easy to see the the underlying highway. if you plan a route from Berlin to
> Mardrid, then zoom out and see the whole route - then it's not so beautiful
> anymore. But can any mkgmap created map actually route from Berlin to
> Madrid without via points? It's a long time that I looked at mgkmap created
> maps for car routing and some years ago this was not possible.[/qoute]
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-- 
Felix Hartman - Openmtbmap.org & VeloMap.org
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