This is a basic navigation exercise that focusses on grid references, distance and bearing. It is supported with a Powerpoint pack, a Word document and an Excel spreadsheet. They can be downloaded in this navex zip file.
The Powerpoint pack contains the maps and a custom Romer.
The Word document contains a worked example, plus four sets of exercises. An answer sheet is also included.
The spreadsheet provides two main capabilities. First it builds inter-checkpoint tables of distance and magnetic bearing. Second it builds route tables for a series of checkpoint pairs.
The spreadsheet may be re-used for any direct path distance and bearing calculations for other events. Enter the grid references of the waypoints for the event, the magnetic variation, and then the required route segments.
The Map
The map used for the exercise (slide 2 in the powerpoint pack) presents a coastline, a number of checkpoints labelled A through Y, a 1000m grid and some indicators of magnetic north.
The distinction between sea and land areas is not explicit – the users should be able to discern this from the map features!
The magnetic variation is not shown, as the determination of this is part of the exercise.
Three elements of the map are aligned magnetic N-S, and the Romer should be used correctly to determine the variation.
Slide 3 contains a custom Romer. This slide and the map should be printed without scaling to ensure alignment of the dimensions. Print the Romer on transparency if available.
The Romer MUST be used to obtain correct grid references. Eyeball estimation, or just guessing, will not suffice.
The powerpoint pack also contains a version of the map without any checkpoints, which may be used for a plotting exercise, as well as maps showing the routes used in the example and set exercises.
The Exercises
The Word document contains an instruction example and four sets of exercises.
Each set contains 15 questions, and describes a route which must be located on the map. The questions are a mix of grid reference and distance+bearing.
For each set, it is also required to find an alternative route for one of the route legs, due to direct travel not being possible.
The whole exercise should take a team learning these tasks about 45 minutes to complete. An already competent team could accomplish it in less than 15 minutes.
The Spreadsheet
Preparing this type of exercise can be quite time consuming, especially calculating inter-point distances and bearings. And without making mistakes too! The navex spreadsheet removes all the dreary grunge work.
Grid Reference Entry
The GridRefs sheet is the primary data entry location.
Magnetic variation is entered in cell C3.
The grid references for each checkpoint are entered in the GridRef column of the table.
Grid references assume a 1000m grid. Four-, six- and eight-figure grid references may be entered. The columns to the right perform the appropriate scaling to convert to a standard measure.
Distance and Bearing tables
The Distance and Bearing sheets contain the cross-tabulation of these values between each and every checkpoint.
The From checkpoint is listed down the left column, and the To checkpoint is listed across the top row. To find, for example, the distance from M to T, locate M in the left column and move across until under the T in the top row, locating a value of 0.9. The distance table of course is symmetric, but the bearing table will have a 180° difference between the two directions. The magnetic bearing from M to T is 155°, and from T to M is 335°.
Route Tables
The Route sheet allows extraction of distance and bearing between a series of checkpoint pairs. The grid reference of each checkpoint is included in the lookups.
This facilitates the preparation of exercises such as presented in the Word document.
