| VIDEO | AUDIO |
| OPEN WITH A WIDE SHOT OF DEEP WOODS. A LT.
COLONEL, IN FULL GEAR, COMES INTO VIEW. HE PORTRAYS ALL THE ACTIONS DESCRIBED IN THE
COPY. (IN THE BACKGROUND, FAR AWAY, IS THE SOUND OF A HELICOPTER.) |
Anncr: Imagine the following scenario: You're a downed
pilot, in a foreign country. You need help and you need it
now. You radio your situation. A helicopter will be sent to
pick you up. Call back with your location. You retrieve your
hand-held GPS receiver. Its readout gives you specific
coordinates. You call the helicopter; here's my location. The
pilot acknowledges your position and tells you he'll be
overhead directly. But after too much time passes, after he's
nowhere in sight, you realize something is drastically wrong. |
| WIDE SHOT OF PLATOON LEADER ON THE RIDGE OF A FIELD WITH BINOCULARS. CUT TO WIDE SHOT OF
GROUP OF BUILDINGS FAR AWAY. CUT BACK TO MEDIUM SHOT OF LEADER REVIEWING MAP AND
MAKING CALL. CUT TO WIDE SHOT OF SHIP OFFSHORE. CUT TO MEDIUM SHOT OF SPECIALIST
IN APPS ROOM. CUT TO WIDE SHOT OF AN FA-18 FLYING. CUT TO WIDE OVERHEAD SHOT OF FIELD BEING BOMBED. |
Imagine another scenario: You're a field commander. Your
mission - to eliminate a group of buildings some 5 kilometers
west of your position. You plot their location on your map
and call for an air strike. Onboard an offshore Navy ship, an
Intelligence Specialist feeds your coordinates into his APPS -
a very accurate imagery based system used for targeting.
Minutes later, the first missiles from an FA-18 arrive,
exploding only 100 meters from where you're standing. And
that's when you realize how important it is to know your
datums and grids. Because knowing what these terms
represent could save your life. |
DISSOLVE TO ANIMATED GRAPHIC:
DMA PRESENTS:
DATUMS AND GRIDS -
MAPPING AND CHARTING TOOLS
OF THE 21ST CENTURY. |
SOUND: Swelling music introduction. |
| OPEN ON WIDE, TRACKING SHOT OF SPOKESWOMAN IN TYPICAL DMS CLASSROOM. |
Anncr: Datums and grids. What are they? And how can you
use them to locate specific targets? For the next few minutes,
we'll give you an overview of how maps and charts are
made... why they can differ from each other... how they relate
to the GPS - the global positioning system... and what you can
do to ensure your coordinates are in sync with everyone
else's. |
| ANIMATION OF GLOBE WITH DATUM GRID SUPERIMPOSED OVER IT. |
To begin, we need to define our terms.
What is a datum? Simply put, a datum is a mathematical model of the earth...that is, a base reference.
We use this model as the basis for the coordinate system you see on maps, charts and precise surveys. |
CUT TO CLOSE UP OF TYPICAL DMA MAP. OVER THAT SUPERIMPOSE GRAPHIC: WORLD GEODETIC SYSTEM
1984 - WGS '84. |
The datum the Department of Defense uses today is called
the World Geodetic System - 1984, or WGS 84. The Defense
Mapping Agency produces all of its new maps and charts with
this system. |
| CUT BACK TO ANIMATION OF GLOBE. SHOW DATUM GRID AS BEFORE, THEN ADD NEW GRIDS IN
DIFFERENT COLORS. |
Not all countries use WGS 84 however.
Many use their own datum when they make their maps and surveys - what are known as local or
regional datums. These nations, in other words, assume the
earth is a different size and shape than we do. Since they use a
different reference, they produce maps whose coordinates do
not agree with those of our maps. |
| CUT BACK TO NEW TRACKING SHOT OF SPOKESPERSON, NOW IN A DIFFERENT CLASSROOM. |
In addition, WGS 84 is a relatively new reference system, and it will be years before all Department of
Defense maps are updated to use this global datum. Older
U.S. maps, and foreign maps, all using different datums, are
still in use by military forces. That means that the coordinates
derived from a map or weapons system using one datum will
differ from the coordinates for the same point taken from
another datum. |
| SPLIT SCREEN SHOWING CLOSE UPS OF THE TWO
DIFFERENT MAPS. THEN SHOW TWO DIFFERENT GRID PATTERNS OVER THE SAME LOCATION ON THE MAP. |
Sometimes this difference can be huge. In this example, the
same set of buildings is plotted near the margins of two maps.
If you plot the coordinates for the buildings on each map,
you'll get two different locations ... locations that differ from
each other by 755 meters. Why? Because the top map uses the
WGS 84 datum. The map on the bottom uses a local datum,
in this case the Tokyo datum. |
