--- In ScoutRadio@yahoogroups.com
, "Robert Bruninga" <bruninga@...>
> - Minimize weight by carrying a paper map of the route with a
> few lat/longs of features along the way. Then manually estimate
> your position on the map and send out a position when you want
> to report, at your convenience or when on a hilltop.
On a somewhat related topic, a good skill for Scouts to develop is
the ability to use a GPS together with a paper map. Combined they
make a better resource than either alone. There are some tricks to
doing this easily.
First, set your GPS to display its position in Universal Tranverse
Mercator (UTM) grids. The advantage of this system is that they are
always linear (by comparison, longitude lines converge) and work up
and to the right to ease plotting. In addition, the UTM coordinates
are based on meters so distance and travel time is easily estimated
from the resulting kilometer grid. This is how the US military does
land navigation. While you probably don't have to call in artillery
in the Boy Scouts, you can appreciate how accurate it can be.
Second, get a recent USGS topographic map. The ones for the area in
Sussex County mentioned were all issued in the past ten years and
actually have the UTM tick marks printed on them. Use a straight
edge to connect them to grid it before leaving home and you'll be
able to eyeball your location to within 100 meters from the GPS
pretty accurately. Plastic UTM plotters are also available if you
want to locate yourelf down to 10 meters or so.
Third, look at the legend of the map to determine what horizontal
datum was used to make it. Then set your GPS to the same datum for
the utmost accuracy between the GPS and the map.
This makes for a good program for a Scout meeting and can help Scouts
meet the requirments for Camping merit badge. And, of course, we
hams can make a pitch for Radio Merit Badge while explain how the GPS
system uses radio waves to determine position.
Gary Wilson, K2GW