So, I did a little bit of math to see how much area my maps are covering, and how many tiles they take.
A USGS topo map for the Big Bend area covers about 60 square miles, and takes 4981x5682 pixels (I converted the PDF to a .png at 250 dpi with imagemagick to get these pixel counts). That will be 5x6 tiles of 996x947 pixels each, right? Thats a total of 30 "tiles" of the 500 my Oregon 600 can use. I could fit 16 such maps on my Oregon (really a bit more), for a total of 960 square miles, or an area almost 31x31 miles. That isn't bad.
For the units that allow 100 tiles, that could still take 192 square miles, or an area about 14x14 miles. Still not too shabby, and plenty big for a camping trip.
Note this is NOT the resolution I used for the map I posted above where my measurements indicated about 1 pixel per meter. That is a map at 600 dpi. If I were to use a map at that resolution, they would take about 6 times as much space ("only" about 200 square miles in those 500 tiles the Oregon allows me). But the 250 dpi is really quite adequate for the Garmin's display...the USGS Topo maps are clear at that resolution, and the shade images I generate show nice details not present in the topo map itself...it all comes together quite nicely.
Given I tend to only concentrate my trips in much smaller areas, I can load up several topo maps for many different locations before ever having to worry about running out of space.
A USGS topo map for the Big Bend area covers about 60 square miles, and takes 4981x5682 pixels (I converted the PDF to a .png at 250 dpi with imagemagick to get these pixel counts). That will be 5x6 tiles of 996x947 pixels each, right? Thats a total of 30 "tiles" of the 500 my Oregon 600 can use. I could fit 16 such maps on my Oregon (really a bit more), for a total of 960 square miles, or an area almost 31x31 miles. That isn't bad.
For the units that allow 100 tiles, that could still take 192 square miles, or an area about 14x14 miles. Still not too shabby, and plenty big for a camping trip.
Note this is NOT the resolution I used for the map I posted above where my measurements indicated about 1 pixel per meter. That is a map at 600 dpi. If I were to use a map at that resolution, they would take about 6 times as much space ("only" about 200 square miles in those 500 tiles the Oregon allows me). But the 250 dpi is really quite adequate for the Garmin's display...the USGS Topo maps are clear at that resolution, and the shade images I generate show nice details not present in the topo map itself...it all comes together quite nicely.
Given I tend to only concentrate my trips in much smaller areas, I can load up several topo maps for many different locations before ever having to worry about running out of space.