Traditional Land Navigation

Introduction:

On Monday March 5^th we conducted our first land navigation field activity using traditional methods.  The only tools needed for this technique were our maps created during last week’s activity and an orienteering compass.  Although this technique is considered archaic when used alongside new age technology, it is highly reliable and if done correctly very accurate.  Land navigation with a compass and map is to this day still a fundamental skill used by our Armed Forces.  During times when your Blue Force Tracker or Dagger GPS malfunction, the next reliable alternative is compass/map navigation.

Methods:

Having already created our maps and recorded our pace counts, the next process in this exercise was to plot our points.  The points were given to us in 6 digits for both the X and Y coordinates making it very easy for us to use our UTM reference grids.  Once the general area within our 20X20 meter grid cells was located, we could easily interpolate an even more accurate location of the point.  Figure 1 below shows all six of the points plotted on our aerial image map.  Point 1B was our starting location just outside the Priory building.  After we all plotted our points individually on separate maps, we were able to compare them with each other to minimize error in plotting.  

Figure 1: Our map after plotting the 6 points. Point 1B on this map was moved slightly to the north after this image was taken.

After plotting, we determined the azimuths connecting all six of our points.  An azimuth is simply the straight line direction between two points with units of degrees or mils. The technique I used involved a military protractor.  Figure 2 shows me finding the azimuth between two points.  Using the protractor, you simply place the middle crosshair on your point and parallel to the grids. Next, use a straight edge to record the direction in degrees found on the outside edge of the protractor. 

Figure 2: This image shows me finding the azimuths to each of our points using a military protractor. If you look closely you can see a small nylon string going through the center of the protractor. This string is used for on the fly azimuth calculations without having to draw a line between your points or use a straight edge (as shown in this photo).

Another method of determining an azimuth is by using your compass.  Figure 3 is an orienteering compass like what was provided to us.  To find an azimuth simply place the compass on your map and use the straight edge of the base plate with the direction of travel arrow towards your point. Next twist the bezel with index lines so that North is oriented to North on your map and the index lines are parallel to your grid lines.  To find your azimuth, turn the compass so that the magnetic needle is inside of the orienting arrow and you can read your bearing using the index line.

Figure 3: A standard Orienteering compass. The compass housing with degree dial is what I referred to as the bezel.

We now know the location of our points and the direction we need to travel to find those points; however, we do not know the distances between the points.  To find the distances I used a scratch piece of paper to mark the previous point and the point we are trying to find.  I then used these marks to determine the distance in meters with our scale on the map.  Note that there was a problem we ran into during this process that will be explained below in the discussion portion of this report.  Having found the straight line distances between each point, we can then use our pace count to determine where we are on the map.

Having the points plotted, direction of travel determined, and distances to each point recorded, we were ready to head out after our first point.  We began at the starting location (figure 4)  and used the compass to orient ourselves in the direction of point 2B and started walking with our normal paces.  It wasn’t long before we came across our point (figure 5).

Figure 4: Oscar Mike to location 2B

Figure 5: Point 2B. At each point was a small orange marker with a patterned hole punch.

                                                                         

After we found a point, we simply rotated the bezel on our compass to align with the azimuths we previously wrote down and began measuring out our paces.  It took under an hour to find all five of our points.  The images below show us trekking in snow at times knee deep and successfully finding all of our points.



Navigating toward a point in some rough terrain.

Joe punching our last point before we head back to the Priory building.

Discussion:

There were a few complications involved with our compass/map land navigation.  Once at the Priory, we realized that the UTM grids being used were projected so there would be a small difference between grid North, True North, and Magnetic North.  We found out that the difference between grid north and Magnetic North was about three degrees.  To account for this we simply subtracted three degrees from our recorded azimuths.  This difference between grid north and true north is known as the angle of declination. For our area it is generally only half of a degree but due to the projection of the map it was increased slightly.  

Another problem we ran into involved determining the distances between the points on our map.  The scale on our map had intervals that made it difficult in accurately determining our distances.  Each mark on the scale was equal to 18 ¾ meters on the ground and 100 meters was not explicitly defined making it difficult to associate with our pace counts.  That being said I need to note that throughout most of this activity we stopped using our pace counts.  Our paces were much different as we zig-zagged through brush and up and down hills. We found it easier to simply turn around and estimate how far we traveled in a straight path. 

Conclusion:

This form of land navigation provides a very simple and accurate way of finding locations on a map.  Our group was able to find all 5 of our locations in under an hour.  This exercise provided very good training for our final land navigation activity to be conducted on March 25^th.  Land navigation is a very useful skill for geographers. This technique can also be applied to various disciplines of geospatial technologies such as the surveying project previously conducted.