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

Wed May 5 08:32:52 BST 2021

Really, routing over long distances on highways? I haven"t met people using
a Garmin GPS device routing via highways - however many who use it for
recreational purposes - so routing over short distances.

Anyhow if you use a lower DP value no problem there. It's mainly if you
zoom out to overview map resolution at 18, 17 or wherever that starts. So
far mkgmap maps were unusable on devices for 17 or lower due to being very
slow. I'm not sure how much of this was too much data in those tiles, and
how much that the device has to look up too many tiles. That's what the
device is using the basemap for, and Basecamp using the overview map for.
So if you zoom out that far - no problems if the route doesn't fully follow
the underlying map. It's the same for Garmin city navigator maps.

On Wed, 5 May 2021 at 15:27, Thomas Morgenstern <webmaster at img2ms.de> wrote:

> Hi all, I see this completly different :  many people use osm data for
> routing.   Routing is the main purpose  for using OSM. If routing [ *quote]
> : ** it will look a bit strange [end quote] *is not akzeptable.
>
> Thomas
>
>
> Quote :.............
> So yes with very high DP values and lots of simplification if you plan a
> car route over highways, at some point it will look a bit strange. But
> again, very few people use Garmin maps for car routing nowadays, and even
> less car routing based on OSM data. ......
>
> On Wed, 5 May 2021 at 14:29, Gerd Petermann <
> gpetermann_muenchen at hotmail.com> wrote:
> Hi Felix,
>
> I don't think that it only depends on the typ file. Programs like
> GpsMapEdit also show wrong merges.
>
> Reg. roads: Seems RoadMerger also doesn't reverse points, I didn't notice
> that before. So, I have two methods to improve.
> It's quite difficult to understand the effects because we
> - merge roads with equal attributes
> - possibly split those roads again to avoid loops or too long roads or too
> complex roads (too many connections) or other limits in IMG format (this is
> needed for routable maps,  maybe not for others)
> - possibly merge again at levels > 0
>
> I have to think about this again. Maybe there is no problem with the NET
> file changes when this last step is done. The NET file contains "pointers"
> to the RGN file for each level in which the road is rendered. So, if a road
> is rendered at level 1 the data in NET allows to show all the road labels.
> Maybe that's all and there is no further effect (esp. not on routing), but
> maybe the info is also used when you create route in Basecamp. I guess it's
> not.
> I have no idea what Garmin software does when a road has pointers to lines
> at levels 0, 1, and 3 but not at level 2. I found no such case in Garmin
> demo maps. I think that could happen when I don't add code to prevent it.
> Probably it doesn't matter much when RoadMerger is allowed to reverse so
> that we have fewer parts which could be merged later.
>
> Gerd
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-- 
Felix Hartman - Openmtbmap.org & VeloMap.org
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