Mapping in the New Age Part II
David Pease, Advanced Rescue Technology Magazine
I first would like to share some information that all Instructors like to hear from classes they have taught. Several weeks back, I taught a heavy truck rescue class at the Cooper’s Fire Department in Nash County. On Friday of the following week, I received a phone call from Assistant Chief Jamie Moss, in reference to a motor vehicle crash that occurred on Wednesday of that week. Apparently a tractor trailer had swerved, crashed and the driver was pinned. They were able to put into play the training we had done the weekend before, to free the pinned driver. I felt good that the training we had done paid off so soon with their department. I think it always gives an Instructor gratification when the training you help to do, actually pays off.
In the last article we talked about topographical maps in general. I have come to realize that a third article may be in order to allow for the coverage of basic information. I want to be able to discuss several of the computer mapping programs that are available for rescue, search and fire usage as well. Delorme and Maptech both offer computer mapping programs that we will discuss in our third article.
When using topo maps and ortho maps you need to have a reference system that will allow for you to find and plot things on the map. There are several systems that can be used, and some are more common than others. We will mention most of them but only discuss the two most commonly used. In order to plot on a map you must have a system that allows for someone to measure distances from fixed points from at least two directions and intersect them on the map. The two most common systems are latitude / longitude and the UTM (Universal Transverse Mercator) system. Both use grids and reference marks found on a typical 7.5 minute topographical map. The topo maps have reference marks on the perimeter to indicate these reference points.
Latitude and longitude was established in the late 1800’s by those wanting to develop a navigational system for travel, primarily for ships. First they drew a line from the North Pole to the South Pole forming a half circle and called it the prime meridian. On the other side they did the same and connected a line calling it the International Date Line. The prime meridian was to be considered zero. The angular distance to be measured either east or west to any point of this longitudinal line on the surface of the earth is up to 180 degrees in either direction to the International Date Line. Next, we have the latitude line that ear marks zero, and that is the equator. This line completely encircles the earth. Distances of angle either north or south of the equator are measured and have a maximum of 90 degrees at each of the poles. Latitude lines are parallel to the equator. Now in plotting a point using this system we now know that one degree equals 60 minutes and one minute equals 60 seconds. If you can plot to within a second, then your accuracy would be within a 1000 square feet. If you plot north of the equator, which we would, then you might have a reading like; 48 degrees north, 22 degrees east or 48N, 022E. The Lat/Long system is used worldwide for navigation and SAR work and is easily recognized. Topo maps are grided for latitude and longitude.
Another excellent system to use is the UTM system. This system is used by the military and is becoming more popular for SAR work. The USGS topo maps have a marking along the border that represents 1000 meter grids. These will appear as short black lines. On military maps these lines are connected to show grids, while on the standard USGS maps, they do not have the grid lines. Each of these small hash marks has four numbers beside them. Two of these numbers are small case numbers while the other two are large case numbers. The smaller size numbers represent 1,000,000 and 100,000 meter grids. The larger size numbers represent 10,000 and 1,000 meter grids. This now gives you a reference to plot on the map. By using these numbers we can find a location on the map within 1000 square meters, which again is good for ground SAR work.
Let’s look at an example to see how this works. If I were to give you a point on the map of 357753, you could then plot a fairly accurate point on the topo map. We will take the first three numbers for our beginning reference as 35.7 and find in the larger cased numbers across the top or bottom of our map the number 35. We will then measure 7/10 of the way from point 35 going from left to right, to the next tick mark of 36. That is our first point. Next, we will take our second set of numbers and find our second point. You take 753 then convert to 75.3 and measure 3/10 of the way from point 75 to 76 going from bottom to top of the map. Where these two lines intersect is now your point. This system can use 8 numbers which would bring you to a 100 square meters. When using this system on a standard USGS topo map, you will have to draw grid lines to connect the tick marks. This should be done to your maps prior to using them in the field. There are also several templates available to use with this system. These are small transparent squares with grided lines that can be laid over your topo map. These are excellent for plotting points on your map. Most good compasses also have a 1/24,000 ruler on the base plate that can also be used for plotting UTM.
There are several other mapping systems that I will mention for general knowledge. The SDMRT System was devised by the San Diego Mountain Rescue Team. This system uses the technique of simple measurements from the borders of the map being used. As long as the maps used have a border, this system can be used. A measurement in inches is taken from the top or bottom then from the left or right side to plot a point. Another system is the Uniform Map System or UMS. This system was developed in Washington State and is the official system of their SAR teams. This system uses Sectional Aeronautical maps that are broken down into a grid system. Because aircraft are familiar with these types of maps, it makes for easy exchange of information and locations from ground units to air units. Depending on where you go to search, the types of maps and systems used could vary. Overall, the UTM system is probably the most widely used system for plotting on a map. Most GPS units are set up to read UTM as well as Latitude and Longitude. The computer mapping programs are also set to use either UTM or Latitude and Longitude. Both Delorme’s and Maptech’s mapping programs use both these systems. This gives the searchers the capability to utilize their GPS units with the mapping programs.
You will need to have a good background in compass work to be efficient in map techniques. You should have an orienteering compass that can be used with the topo maps. Since this article is not on compasses and their use, we will not spend time getting familiar with the use of a compass. Before getting into the map and compass field you should get some training in land navigation and the use of the compass and the map. There are a lot of good classes available and Instructors to teach them. NASAR offers several good search classes that include the use of map and compass. There is also some good reading out there on the subject, such as “Search and Rescue Fundamentals, Third Edition Revised”, available through NASAR. Also, “GPS Made Easy”, by Lawrence Letham, and “Advance Search and Rescue” another publication through NASAR.
In our next article we will take a look at the mapping programs that Delorme and Maptech have to offer and some of what they can do for you as a SAR Technician or firefighter dealing with a large wildland fire. In the meantime, always train to your best, keep safety in mind and stay safe.