GPS is a navigation system based on 24
satellites that orbit the Earth they are
owned by the United States government
and were originally for military
purposes but they were made available to
the public around the year 2000 each
satellite sends a signal back to the
earth but they cannot pass through solid
objects like mountains and buildings but
also less accurate around trees the GPS
unit I have here is a garmin etrex 20
first I've got to turn the GPS on I push
four spots on here and it takes a little
while to load so we'll just wait then
the unit will begin searching for
silhouette signals the GPS receiver must
lock and at least free signals to work
the more signals you get the more
accurate your position each cell light
has a number representing a specific
cell light and space for satellites in
the middle of the bull's-eye are much
closer to you bin the Semites outside
the bull's eye as the GPS acquires
signals the strength of each signal is
represented by the bars on the Biograph
at the bottom of the screen if you got
white bars it would mean that the GPS is
still trying to get the signal a we have
orange bars which means that the GPS has
already acquired the signal tool bars
shows stronger signals and short bars in
this case we've got many toolbars
therefore this site has got a pretty
good signal when the GPS is at least
free signals your latitude and longitude
coordinates appear at the top of the
screen and the top right you can see how
accurate your signal is here you can see
that the signal is accurate to within
three meters but GPS has many other
useful functions including a stopwatch a
trip computer page
now on this trip computer page you can
also see that the GPS has an altimeter
you can see here where to our elevation
of 314 meters above sea level the GPS
also has area measurement a calculator
alarm map compass and so on and what I'm
doing here is I've just won the belt
into the middle of stream here because I
want to demonstrate the impact path an
overhanging ledge might have on the
signal for GPS and when I push the
Semite search it takes a little bit
longer to acquire two signals
I'll see four more of a white fires here
that means the GPS was still trying to
find a signal now I have a quarter
signal now but it just took a bit longer
bender did in the previous site so as I
said before when you need to buildings
for really big trees or rocks you may
lose your signal together so all you got
to do is you got to move somewhere else
until you find a signal today I want to
focus on marking waypoints which is
simply the location you want to reach
I'm starting here
quite a thorough and accurate which is
not far from the corona key Forest Park
then the North Island of New Zealand I'm
going to mark this point here
there's my Waypoint we're not going to
show you how I can get myself lost
somewhere in a paddock nearby and then
use my GPS to find my way back
now I met my new location I want to find
my way back so I'm going to go onto the
map here and you can see where I am on
the map but we need to change the scale
somewhat so we can see a clearer so
you've got these arrows just on the
left-hand side of the GPS and you can
alter the scale so I've just gone from 2
kilometers out and I am going to come to
about 80 meters now the GPS will show me
how to get back to my way point in a
straight line you can see this pink
straight line down the bottom of the
screen here it does not take into
account features I need to avoid like
obstacles such as streams or
impenetrable forest the arrow here shows
where I am now and the straight line
shows the location of where I started
the good news is as I change direction
the orientation of that line will also
change position so I still know the
overall direction I need to be heading
and Here I am the GPS has just signaled
to me that I have arrived we're back at
the beautiful stream where I began