Yes, you need routable maps if you want your GPS to actively
assist you with navigation. Non-routable maps just show things,
like paper maps do.
What's "NA"? North America.
All longitudes from Greenwich west to the international date line
are negative, just as all latitudes south of the equator are
negative.
Being east of Greenwich, India has positive longitudes.
Apparently, this is a difference between astronomers and geographers.
Astronomy uses west long as positive. From a professional astro site:
IMPORTANT -- BEWARE OF THE LONGITUDE SIGN CONVENTION. The
longitude returned by slOBS is west-positive in accordance
with astronomical usage. However, this sign convention is
left-handed and is the opposite of the one used by geographers.
I am an astronomer.
Looking at the /Garmin/Lambertus Index of OSM files, I see maybe 50
files in subfolders and the main folder. Nothing is marked for NA or the
USA. The lat/long values on the file names are of no help. I would
expect one of them to correspond to the img file in the next paragraph.
Plugging the 200 into my usb cable, I see Diag, Help, Vehicle, Debug,
Voice, etc. folders. In the main folder there are a gmapbmap.img (6M)
and a gmapbmpa.sum (1K) file. Two others for the prom.
The short answer is "yes". They show whatever OSM contributors
have added, including streets and POIs. If you want something
fixed or something else added, consider becoming an OSM
contributor yourself. See
www.openstreetmap.org
Look at the "Getting Started" page of your owners' manual,
available here:
Mine has disappeared but thanks for the link. I'll take a look.
http://www.garmin.com/manuals/nuvi200_OwnersManual.pdf
I notice that it might be either a full-sized SD card, or a much
smaller micro-SD card. You'll need to check.
You need to be looking at the folders and files on the SD card,
not on the Garmin hardware itself. That should come up as a
separate drive when installed and then connected to the PC.
The only think I see that might look like a memory card is on the bottom
where the serial number bar code is located. The manual has several
reference to the card, but not a single statement on how to get at it. I
tried push on the slot, but nothing happens. It seems quite rigid. My
guess is there an internal SD and that's it. All the folders on files
are on it. See above where I name some of them.