Revision Exercises

 

Personnel Required

  • 1 - 2 crew

Equipment required

  • 1:25000 topographic map
  • Bega Map
  • Magnetic compass

Adapted from and many thanks to: Alan Burdon - Cobargo Brigade

  1. From the information panels on your Bega map fill in the answers in the table below

  1. Locating a fire from observed bearings (Triangulation)

Observers at the three positions have spotted smoke and have taken compass bearings:

  • Find the grid positions on the map.
  • Calculate grid bearings from the magnetic bearings. (assume a 14° magnetic variation)

  • Using your protractor, plot lines from the observation points towards the incident using the grid bearings.
  • Find the grid reference of the point where the lines intersect (N.B. They are unlikely to meet at a point because of error but should form a small triangle. Give the reference of the middle point).

GR = ——————————

Finding your position by bearings to observed features (Resection)

You cannot be certain of your position but can see and identify three notable features:

Dr George Mountain, Tathra Water Reservoir (next to the Fire Station) and the Intersection Dr George Rd and Bermagui Rd.

  • Find these features on the map.
  • Calculate grid bearings from your magnetic bearings. (assume a 14° magnetic variation)
  • Calculate a back bearing (bearing +/- 180 {your answer can’t be more than 360°})

  • Using your protractor, plot lines from the features towards your supposed position using the back bearings you have calculated.
  • Find the grid reference of the point where the lines intersect

GR = ——————————