[OSM-talk] Fwd: [OSM-dev] Ideas for OSM enhancements

[Karl Newman]

Forgot to reply-all to the list.


---------- Forwarded message ----------
From: Karl Newman <siliconfiend at gmail.com>
Date: Dec 31, 2007 9:48 AM
Subject: Re: [OSM-dev] [OSM-talk] Ideas for OSM enhancements
To: Igor Brejc <igor.brejc at gmail.com>


On Dec 30, 2007 11:05 PM, Igor Brejc <igor.brejc at gmail.com> wrote:
> Karl Newman wrote:
> > osm files. Those files could then be processed by mkgmap. Garmin
> > devices currently only support up to 2 GB MicroSD cards, but you're
> > more likely to run into the limit of 2025 map segments first. We
> > probably won't have the luxury of making the tiles uniform size,
> > because obviously urban areas will have much more road density than
> > rural areas. But if we were able to chunk it up into 4 degree square
> > sections (obviously quite large near the equator), the planet could be
> > covered in 4050 sections (360 x 180 / 16). Obviously, ocean areas will
> > subtract a significant number from that.
> >
> Hello,
>
> I'm not sure the memory capacity on Garmin units is the only (and the
> main) limitation. What about the processing power? Loading a huge amount
> of map data onto a unit probably slows down its processing (map
> rendering, for example). I haven't tried uploading a large map on my
> Garmin, but I'm wondering if it affects the performance? Have you had
> any experience with it?

Well, the key is clutter management--hiding less-important features
when zoomed out. That's all supported by the programs which create
custom Garmin maps (such as mkgmap). My Vista HCx has Garmin's
commercial package of street maps for all of North America in it
(around 1.5 GB) and it's snappy enough.

> And one more thing: how long would it take to upload a large map? Even
> for small maps (20 MB) it takes about minute or so.

For the units with MicroSD cards (up to 2 GB capacity supported),
you'll be much better off using an external card reader so you can
transfer at USB 2.0 speeds instead of Garmin's built-in 1.0 speed.
Compiling the maps into a single gmapsupp.img file to prep for
transfer still takes quite a while, though--no way around that except
a faster computer.

Karl