Transcript Land Navigation

Professional Military Education
Initial Entry Training
Land Navigation
and GPS Usage
References
FM 3-25.26
Map Reading and
Land Navigation
Overview
• Introduction
• Map Coordinates
• Determining Distance
• Finding Correct Direction
• Finding Your Position
• Relief And Elevation
• GPS Usage
Land Navigation & GPS
To avoid getting lost, use:
• Map.
• Compass
• GPS
• Other ways to find
directions
• Common sense
Land Navigation & GPS
Three things keep you from getting
lost:
• Finding your map coordinates
• Determining distance
• Finding the correct direction
Finding Map Coordinates
A map is a drawing
of earth's surface.
Maps show natural
and man-made
objects by symbols
Symbols are
explained in the
lower left hand
corner: "legend."
Finding Map Coordinates
• Black lines running up
and down (north and
south) and crosswise
(east and west).
• Lines form small
numbered “grid
squares”
• Using these numbers,
you can identify each
grid square.
Finding Map Coordinates
• Read Grid Square
numbers from left to
right along the bottom
• Locate the line that
borders the grid square
on the left.
• Read up and find the
east-west line that
borders the grid square
along the bottom
Finding Map Coordinates
•82
•81
• Halfway between line 11
and line 12: first added
number is 5 and the first
half of your location is 115
• Three tenths of the way
between line 81 and line
82; second half is 813.
• Your location would be
115813.
Finding Map Coordinates
The coordinate
scale and protractor
is a square piece of
clear, thin plastic
which helps to
measure small
distances inside
grid squares.
Determining Distance
• Maps drawn to
scale, printed at
bottom and top
of the map.
• Scale 1:50,000
means 1 inch on • Use paper to mark the points
between two points.
the map equals
50,000 inches
• Put paper beneath bar scales
and read the ground distance
in miles, meters, or yards.
Determining Distance
• Distance around a
curve, use paper
to make tick mark
at start
• Pivot the paper
• Repeat until you get to
around each curve
point B, following along
and continue along
the road's edge with
the road's edge
your paper.
• Compare to scale
Determining Distance
Measure distance by counting paces.
Average person uses 116 paces for 100 meters.
Determine your paces on a 100-meter distance.
Rough terrain uses more paces, usually about
148 instead of 116.
• Pace yourself over at least 600 meters of crosscountry terrain in order to determine paces
• Know how many paces it takes you to walk 100
meters on both level and cross-country terrain
•
•
•
•
•9
Determining Distance
• Maintain a straight line by using a compass and
steering points. At night, use compass and stars
• Figure only the straight-line distance when you
have to walk around an obstacle.
• Keep count of the paces taken by using pebbles
or knots (or beads) on a string: Put 10 pebbles in
your right pocket.
• When you go 100 meters, move one pebble to
your left pocket and start your count over.
•9
Finding Correct Direction
• Azimuth is direction from
one point to another, on
map or on ground.
• Azimuths are given in
degrees in a clockwise
direction.
• Due east is 90o,
• 360 degrees in circle, so
due south is 180o,
your azimuth can be any
due west is 270 o,
number up to 360o.
due north is 360 o
Finding Correct Direction
• Draw a line from your
position to a location
indicated ion the map.
• Line up the protractor
with the 0 o point on your
position and the crosscenter lines parallel with
the grid lines.
• The line indicates the
azimuth in degrees.
Finding Correct Direction
• To return to previous
position, take a back
azimuth by subtracting
180 o from the first
azimuth.
• If you cannot subtract
180o from your first
azimuth because the
number is less than 180 o,
then add 180 o.
Finding Correct Direction
• Compasses indicate
Magnetic North and maps
indicate Grid North (based
on flattening of round
surface to flat map.)
• Grid North and Magnetic
North are usually a few
degrees off from True
North.
•9
Finding Correct Direction
• Difference in degrees
between Grid North and
Magnetic North is shown
at the bottom of the map
as the “G-M angle.”
• Newer maps shows how to
change grid azimuths to
magnetic azimuths and
magnetic azimuths to grid
azimuths.
•9
Finding Correct Direction
• Use your compass to find or
follow an azimuth.
• The compass arrow points
towards magnetic north. Avoid
any mass of metal such as a
jeep, a truck, or electrical power
lines.
•190o
Finding Correct Direction
• To shoot an azimuth, use the
center-hold technique.
• Turn your entire body toward the
object, point the compass cover
directly at the object.
• Look down and read the
azimuth from beneath the fixed
black index line.
•190o
Finding Correct Direction
For more information, see FM 3-25.26 Map Reading and Land Navigation
Finding Correct Direction
Shadow-Tip Field-Expedient Method
Step 1. Place a stick in the ground at a level spot
where a distinctive shadow will be cast. Mark the
shadow tip with a stone or twig. This is west.
Finding Correct Direction
Step 2. Wait 10 min. until the shadow tip moves a
few inches. Mark the new position in the same way.
This second shadow mark is always east.
Step 3. Draw a straight line through the two marks
to obtain an west-east line.
Finding Correct Direction
•Step 4. Stand with the first
mark (west) to your left.
The other directions are
north to the front, east to
the right, and south behind
you.
•Step 5. Draw a north-south
line perpendicular to the
west-east line.
Finding Correct Direction
Watch Method
• In North temperate zone, point
hour hand toward the sun. Your
south line is midway between
the hour hand and 1200 hours,
standard time.
• If on daylight saving time, the
north-south line is found
between the hour hand and
1300 hours.
Finding Correct Direction
Watch Method
• In the South temperate, point
the 1200 hour toward the sun,
and midway between the 1200
hour and the hour hand will be
your north line.
• If on daylight saving time, the
north line lies midway between
the hour hand and 1300 hours.
Finding Correct Direction
Star Method
• At night, locate north by finding
Polaris, the North Star
• First, find the Big Dipper.
• Last two stars of cup point at
Polaris, about 5 times out as the
distance between those two stars.
• Facing Polaris, you are looking
north, with east on your right and
west on your left.
•North Pole
•Polaris
•17
Finding Your Position
Resection
• Orient map as closely as possible to
true north.
• Find feature such as the water tower
(A) that you can find on map.
• Put ruler on the map, place edge right
next to the water tower symbol (B).
• Align the ruler so that it points at the
real water tower.
Finding Your Position
Resection
• Draw a line along the ruler.
• Find another feature such as the road
junction (C), and do the same thing.
• Lay ruler on your map and point it at
the real junction (D)
• Draw another line along the ruler
until it intersects the first line.
• The intersection is your location.
Finding Your Position
Modified Resection
• If you know that you are located somewhere
along a certain linear feature on the map such
as a road or riverbank, then you can use an
easier method to pinpoint your location—a
method called “modified resection.”
• First, orient your map.
• Locate a feature that you can also find on the
map, such as water tower in previous example.
Finding Your Position
Modified Resection
• Just as before, put a straightedge through the
water tower symbol on the map and align the
straightedge so that it points exactly at the real
water tower.
• Draw a line along the ruler.
• The point where the line crosses the linear
feature you are on is your location.
Finding Your Position
Resection / Modified Resection
• Use your compass, shoot
azimuths to your reference
points, such as the water
tower and the road junction.
• Convert magnetic azimuths to
grid azimuths, determine grid
back azimuths and plot them.
• Your position is where these
grid back azimuths intersect.
Finding Your Position
Intersection
• Intersection method used to find location of an
object that you can see in the distance, such as
an observation post (OP), but is not on your map.
• Shoot an azimuth to the OP using your compass.
• Convert the magnetic azimuth to a grid azimuth.
Finding Your Position
Intersection
• Draw a line on the map from your location along
the grid azimuth.
• Move to another location and shoot an azimuth.
• Convert azimuth from magnetic to grid and draw it.
• OP lies at the intersection,
Relief and Elevation
• Some maps indicate elevation and relief:
slopes, hills, and valleys.
• Check for hills and valleys along the direction
you intend to travel before you start.
• Elevation of a point on the earth's surface is the
vertical distance it is above or below sea level.
• Relief is the representation of shapes of hills,
valleys, streams, or terrain features.
• Contour lines are the most common method
used to depict relief and elevation of the terrain
Relief and Elevation
Contour Lines
• Contour lines are brown lines.
• Lines depicts height above sea level.
• Contour interval is difference in
height (elevation) between lines
• “A” is 80 feet lower than “B”
• Every fifth line is heavier than the rest
and has a number for elevation.
• Rate of rise or fall of terrain feature is
known as its slope.
Relief and Elevation
• When the contour lines
are close together at the
top of a hill, the hilltop is
pointed.
• The hilltop is flat when
contour lines are widely
spaced at the top.
Relief and Elevation
• Contour lines across a stream
come together in a V-shape.
• Map shows water as blue.
• Contour lines determine the
direction that water flows
• V-shape points upstream or
toward high ground.
• Looking for a stream is a good
way to find valleys.
Relief and Elevation
• Lower terrain between two
hilltops is called a saddle.
• Saddle is represented as an
hourglass shape.
• Going through a saddle is
the easiest route to use to
get beyond the two hills.
Relief and Elevation
• A ridge is a fairly long, narrow
section of terrain.
• Ground goes uphill in one
direction, downhill in others
• Contour lines that form a ridge
either U- or V-shaped.
• Closed end of contour line
points away from high ground.
Relief and Elevation
• Use contour lines to determine the line of sight.
• Draw a line from point A to point B
• Note that it crosses some contour lines with
higher elevation than both points.
• You know you will not be able to see point B.
Using GPS Device
Earthmate GPS LT-40 (Tac-Pak)
• Verify mapping application is
installed.
• Plug device into a USB port on
your laptop computer
• Configure the device with the
mapping application
• Open the mapping application.
Using GPS Device
Earthmate GPS LT-40 (Tac-Pak)
• Click the Options button on the
toolbar
• Click the GPS Settings tab.
• Select Earthmate or Generic from
Device drop-down list.
• Select US6 in Port drop-down list.
• Click Start GPS button in toolbar
Using GPS Device
Earthmate GPS LT-40 (Tac-Pak)
• Light-emitting diode (LED)
indicates type of satellite info
• Red: acquiring satellite
information.
• Yellow: has a 2-D fix, no elevation
data available
• Green: receiving sufficient satellite
information for full 3-D fix.
Professional Military Education
Initial Entry Training
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