It's been a while since I've done much with Navit. My regular week doesn't include much travelling and I've just not had that much time to devote to it. When push comes to shove, my wood turning normally wins when competeing for my free time. However, I had a chance to play again this week with the latest SVN-2173. I also had an idea of something to try. I downloaded a map of a much smaller area. Normally I get most of the united kingdom, which amounts to about 80MB map. But I decided to try capturing just around about the county I live in. This got me a map of just 17MB.
It's dificult to quantify the differences, as there is no benchmark mode to try. However, my feeling is that the smaller map led to a more responsive UI once I had a route planned. Normally having a route planned causes my n810 to become largely unusable, However with the smaller map it seemed to be better. Not great, just better.
Today I tried a back to back comparison, as I had previously been going on memory of last use, on a different build. And Lots has changed since then. (Look right, there is an rss of the changes going on, and there is normally a lot of activity) So I setup with a short route planned and tried both my regular size of map and a smaller size of map, one after the other. I also used maps cut on the same day, so no diffference in content for the area I'm in.
The main thing I notice is that tapping to go into the menu system seemed to take much less time, I counted something like 10/11 seconds with the large map, and more like 2/3 with the smaller map. (Still not blistering by any standards, but deffinately better). My caviat to this is that I really can't be sure that equivilent provessing was going on each time. GPS signals can be a little wild, and a couple of 'off' readings could of had the unit attempting to replot routes in one test and not the other. However my *feeling* is that the size of map does effect it's performance. Even when showing the same sized area of the map, and plotting the same and similar length routes.
I'd love for other people to try the test and see what they think, am I imagining it? If anyone else tries please let me know what size of maps you compared, and what country etc. In the meantime I'll go chat in #navit and see if the guys there have any idea why it should make a difference. And if they have any ideas for a more scientific test.