crusty posted on Jul 25 2006 at 06:32 PM said:
Well I backed up after seeing the post about the raster map, went ahead and tried it that way, didnt take long at all.
http://www.dwelch.com/temp/frame00103.png
For now I used run length encoding to compress the maps, which helps, esp with these flat colors, but could use a lot more as 11 maps, which dont even get me off of the street I live on, took 2-3mb. Im not pulling them off of the sdram at this point, they are compiled in. something like png would do a good job, no loss of quality like jpg. I am worried about decompression time though.
When thinking about what the gba gps program may or may not have done (I didnt look at the code at all, just the web page), the gba has tile hardware features, you could do a google maps style thing break the map into tiles and only need to manage the tiles that touch the screen. Then again that would work here as well, dont have to have tile based video hardware. I wasnt too efficient memory wise in that I borrowed maps centered on lat/long coordinates every 0.01 degrees. When you move more than 0.005 degrees off center it moves to the next map. There was a band of about 25 pixels around the edge of each map that wont be seen so that is about 30% waste if my math is right. What is really nice about it is that 1) I dont have to be super accurate converting degrees to pixels, just accurate enough to get across the one map, then when it switches to the next map you get a free re-calibration. 2) I dont have to glue the borrowed maps together to make one big map.
Anyway, proof of concept, took an afternoon to get it running, lots of fun. I actually have not taken this one out driving. I simply feed it logged nmea data from my pc...
I should have held off on the embedded gps purchase, oh well. The rikaline looks perfect. I dont see any US prices other than $79.99 though. I think there is a way to get the data out of my cell phone, or some cell phones, but that is a whole other learning process.
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