[email protected] (Bijan) wrote in
GPS knows its own lat/long. It also has a map. Put the two toegther
and it should know the town. It seems to me that the information is
there. The functionality must be implemented.
[top posting fixed]
Yes, the GPS knows it's(your) position.
Yes, in this scenario, the GPS knows the "position" of the town
(e.g. maybe it's the city hall, post office, etc.).
Yes, the GPS has a map, comprised of vector data, that 'describes'
various features, such as roads.
No, that's not sufficient to tell you what town you are in.
Again - think about how YOU would know what town you are in,
without using the GPS. You would either have to know where the
town boundary lies, and your relationship to it, or, for some
cases, it may be sufficient to know what street you are on, if
the street is completely contained within the town.
For a GPS to do the same sort of thing, it would need boundary data
for every town, and the functionality in the firmware to calculate
whether the current GPS position is within the polygon described
by the boundary. Town boundaries aren't regular, thus the data
is required. What could be implemented would be a 'proximity
alarm' to tell you when you are within a certain distance of the
"town's location", but that's not going to tell you whether or not
you are actually within a town, at least not reliably.
For the 'street solution', the existing vector street data would
have to have 'proximity data' included, to enable the GPS to
calculate if the current GPS position is "on" the street
(which it may already be able to do), and a database to be able
to correlate streets with towns, and, without additional data, that
would only work for streets that are completely within the town.
--
Dave Patton
Canadian Coordinator, the Degree Confluence Project
http://www.confluence.org dpatton at confluence dot org
My website:
http://members.shaw.ca/davepatton/
Vancouver/Whistler - host of the 2010 Winter Olympics