I cant wait tell this is a possability, I would tend to look for small maps of high accuricy then detail.
for example I am in crntral washington an there is a lake called lake chelan and I am a boater/scuba diver and garmins mapsource topography software has the shore line at a
state park to be gross angles that ware way off from real life.
if there was way to take waypoints and trackplot dats and even on a simple level generate a
profile of the area this would easly surpass the quality of the uploaded maps.
if a user could submit maybe a photo of the area and waypoints or trackplots of all the docks and a profile of the shore line.
somday there will be a data base where many people can submit waypoint and maybe most importantly trackplot data and this would be applied to constantly updated maps possably on a layer over a basemap.
often there are logging roads that are not on maps or even ones that are but the real road is closed. so you drive down a road and come to a block you can make a waypoint to reflect this and move on, the trackplot would then be post processed to show the type of road, foot trail,poor jeep trail, dirt road, gravel road,
the data base could be self corecting so that if 100 people say that a road is in one place and 1-2 say it is some where else then the vote wins, maybe even add a quality raiting, if some one is using a handheld in dynamic mode(moving) or static where he averages a waypoint for some time(better quality) I have a portable DGPS beacon that can average out to a pretty close mesurement and it also captures range data on all channels.
so if I place this at a location for 20+ hours it has a pretty high level of quality as far as civilian code gps's go.
even if garmin took an old aerial photo and traced the shoreline with a marker it would be better than what they have now.