Chapter 5: Outdoor Safety
Topographic Maps and Compasses (continued)
Plot Your Progress
As you hike into unfamiliar terrain, you can keep your bearings
by taking frequent compass readings and plotting your progress
on a map.
- Note key points, such as stream crossings, to help you
find your way back.
- Pay particular attention when you reach a high point
at the top of a ridge.
- Use the elevation to locate landmarks visible from there.
Learning to set a course and take bearings takes study and
practice. The best way to become proficient with a compass
is under the guidance of an experienced individual.
Global
Positioning System (GPS)
- The Global Positioning System (GPS) is a navigation system
based on a network of 24 satellites. Users with a GPS unit
can determine their exact location (latitude and longitude)
in any weather conditions, all over the world, 24 hours a
day.
- GPS satellites circle the earth twice a day and transmit
information to Earth. GPS receivers use this information
to calculate the user's location by comparing the time
a signal was transmitted by a satellite with the time it
was received. The time difference tells the GPS receiver
the distance from the satellite. By calculating the distances
from several satellites, the receiver can determine and display
the user's location on the GPS unit.
- Once the user's position is determined, a GPS unit
can calculate other information'bearing, trip distance,
distance to destination, sunrise and sunset times, and more.
- GPS receivers are accurate to within 15 meters (49 feet)
on average. Certain atmospheric factors and other sources
of error can affect the accuracy. Accuracy can be improved
with a Differential GPS (DGPS) or WAAS (Wide Area Augmentation
System).
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