[mkgmap-dev] Performance of POI search on the Device

Mon Jul 20 09:53:03 BST 2020

Hi all,

I've still not fond any simple improvement for mkgmap, but maybe a usable work around.
One point is pretty obvious: If you create transparent overlay maps with rather few elements (like boundaries or cycle routes) try to produce larger map tiles.
Example: For a layer containing the european cycle routes you should not produce a gmapsupp with hundreds of rather small tiles, instead create one with maybe 20 tiles or less. I've tried this and I see no impact on search time with such an overlay map while a gmapsupp containing  ~ 1000 small tiles shows a delay of around 20 seconds. The rule is simple: The more tiles the higher the delay.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen at hotmail.com>
Gesendet: Sonntag, 19. Juli 2020 08:39
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] Performance of POI search on the Device

Hi all,

I still try to understand why the existence of a (transparent) overlay map can slow down the search for POI. It seems the more tiles we have in the overlay
the longer the delay. So, it looks like the Oregon performs a sequential search over all tiles in the overlay map. It seems to ignore a global index in that map,
but, as Franco found out, it might stop earlier / work faster when the overlay map contains a few POI.

My 1st assumption was that the transparent flag makes it difficult for the device to find out if the tile contains any data that may be relevant as it doesn't contain the 0x4b polygon. I tried with a semi-transparent map (0x4b polygon written and transparent flag set). Didn't improve anything.
So, another idea is that the POI with address info change the content of the LBL file header because e.g. the list of countries is filled.
Maybe the device checks this.
Looking at this now...

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von franco_bez <franco.bez at web.de>
Gesendet: Dienstag, 2. Juni 2020 18:32
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] Performance of POI search on the Device

Hi Gerd,

here's the bondary-layer with x-center-poi-type=0x2f01
It slows down the search to the same extent as the other poi-types do.
The option does not seem to have any impact.
http://files.mkgmap.org.uk/download/477/dach_boundary_gmapsupp.img
<http://files.mkgmap.org.uk/download/477/dach_boundary_gmapsupp.img>
Ciao,
Franco

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