Mounted search and rescue

[T'mi Fi <tfinkle@erols.com>]

 When we have roads, power lines, heights of land, mountains, rivers 
and lakes, these are often sufficient along with the map and compass for 
us to establish with a reasonable degree of accuracy, where we are on 
the map. In those featureless areas however, where all looks the same 
for miles and miles of slowly rolling bushland, grassland, dessert, 
tundra, swamp etc., the GPS takes over and will give a definitive 
location which then may be plotted on a map (please note that "map" 
remains an important tool).  


One thing that we all must keep in mind is the use of GPS units are an 
enhancement tool for field navigation and not a replacement tool. 
Technology is no where near the point for GPS units to replace the map 
and compass.  Because of satellite coverage, unit placement and blocked 
signals there will connectivity flaws with reception and in many 
situations a person may simply need to move several meters to restore 
satellite signals.  The major down side to GPS Units is the need for a 
power source, but that can be corrected by carrying a few extra 
batteries (generally AA or AAA), which will extend the units operations 
for another 12 to 24 hours.  Even a week's worth of batteries can be 
easily carried in something that takes up less space than a pack of 
cigarettes. 


The Global Positioning System is composed of twenty-four satellites 
20,200 km (12,500 miles or 10,900 nautical miles) above the earth. The 
satellites are spaced in orbit so that at any time a minimum of six 
satellites will be in view to users anywhere in the world. The 
satellites continuously broadcast position and time data to users 
throughout the world.

Using a portable or handheld receiver unit that receives data from the 
closest satellites, the GPS unit triangulates the data to determine the 
unit's exact location (typically in latitude and longitude), elevation, 
speed, and time. This information is available around-the-clock anywhere 
in the world and is not dependent on weather.  The "Selective 
Availability," which made the public GPS less accurate than the military 
GPS, was turned off on May 1, 2000. Thus, the GPS unit you can buy over 
the counter at many retailers is as accurate as those used by the 
military today.

Many over-the-counter handheld GPS units contain base maps of a region 
of the earth but most can be hooked up to a computer to download 
additional data for specific locales, which is a feature quickly is 
becoming a valuable tool to planning section personnel  when developing 
incident action plans.  UTM is becoming the standard with most search 
operations in the United States, however, since UTM deals with meters 
many americans do not understand the mathematical conversions required 
for field application.  On the newest 1:25,000 US topos, 1 mm. would 
represent 25 meters on the ground. Even the most common Silva compasses 
have a mm. scale on one side and this may be used to measure east from a 
grid line and north from the E-W grid lines.

Map and compass skills will and must always be a part of field 
navigation for SAR personnel.  However, the use of GPS units have 
quickly become equally important and with basic GIS functionality 
software programs,  these systems being integrated into search planning, 
high-tech downloadable data is of utmost importance to enhance POD 
efforts.   If you remember, it just a few years ago when laptop 
computers began to make an appearance at ICP's and have now become the 
norm for progressive and/or highly skilled SAR teams.    

Tomi`
TROTSAR Mounted Team
Maryland