Navigation Flashcards
Maps used by ACTF&R
Street directories.
Site maps.
Hydrant maps.
Block and section maps.
ACT bush fire pre-suppression resource atlas.
ACT emergency service agency capital region operational atlases.
General map info to look for
Map title. Scale. Key to adjoining sheets. Legend. North point diagram. Grid reference block. Miscellaneous information.
Small scale vs large scale
A scale between 1:4 000 and 1:10 000 is generally considered large scale.
A scale between 1:100 000 and 1:250 000 is generally considered small scale.
Meaning for every 1mm on the map in real life its the larger number say 100 000mm. Meaning 1mm is 100m. Meaning 1cm is 1000m or 1km.
Measuring distances on a map
Can be done with paper, dividers, rulers or in an emergency a piece of string or your finger.
When measuring straight lines, mark two points on the map, align your piece of paper and transfer those marks to your piece of paper. Then place you paper under the scale to see the distance.
When measuring a route which is not straight, route should be divided into a series of straight lines. Then use your paper to mark each individual section adding to the last. In the end you’ll have a series of marks which will add up to the full distance. Then place you paper under the scale to see the distance.
Contours
Contour lines help shape the ground.
The closer together the steeper, further apart is less steep.
Contour interval will be printed below scale.
Bold contour lines usually represent 100m between.
Some contours will have height printed on them.
Calculating slope from contours
Measure a distance between two points. Then count the contour lines between and find out the height difference.
If say it was 10m height difference over 100m it would be 10:100 or 1:10. Meaning for every 10m walked you will rise 1m in elevation.
Slope angles
Terrain terminology
Determining grid reference
and four figure grid reference
Vertical grid lines are called EASTINGS and increase in value towards the east.
Horizontal lines are called NORTHINGS and increase in value towards the north.
Any grid square is referenced using the bottom left corner.
Each grid line has a two figure value. Combining the two gives you a four figure grid reference. e.g. 7789
This will give you a large area the size of one grid.
Always quote easting before nothing.
Six figure grid reference
As one grid is not accurate enough when trying to find a location we need a six figure grid reference.
This is done by quoting a extra number for both easting an northing. This number is in tenths of the grid square. Use the romer scale on a compass to accurately determine.
e.g. 773895
First 3 figures being easting and second 3 being northing.
What is a bearing
A bearing is a measure of direction in relation to north.
Can be in degrees or in cardinal points.
Compass terminology
Taking grid bearing from map
Place compass on map with directional arrow pointing in direction of bearing.
Align meridian strips parallel with easting on map.
Read grid bearing where index line intersects housing.
Back bearings
The direction from your location to another is called a bearing. The opposite direction is called a back bearing.
Back bearing is found by either adding or subtracting 180 depending if the number is higher or lower than 180.
Over 180 take 180 away.
Under 180 add 180.
Different norths
Grid north is fixed for the particular grid system used for the map series.
Compasses use magnetic north which slightly varies from year to year. Magnetic variation will be stated by how much on the map. With an amount to add for each year since the map was made.
