Important Map Terms A Cadet Should Know

Map Reading Cadet Equipment - Pathfinder Protractor-Romer

BEARING:

The angle, measured clockwise, that a line makes with a fixed zero line.  It may be a True Bearing, measured from True North - a Magnetic Bearing measured with a compass from Magnetic North, or a Grid Bearing measured from Grid North.

COL (SADDLE):

See also SADDLE for description.

CONTOUR: 

An imaginary line on the surface of the ground at the same height above means sea level throughout its length. Contour lines are drawn a map to show the shape of the ground.

CREST: 

The highest part of a hill or range of hills. That line on a range of hills or mountains from which the ground slopes down in opposite directions.

DATUM or DATUM LEVEL: 

The level from which altitudes are measured; generally mean sea-level.

DETAIL: 

All the topographical information on a map.

DIVIDE: 

The line along a range of hills from which the water flows in opposite directions, e.g., the continental divide.

ESCARPMENT: 

The steep hillside formed by a drop in land level, usually at the edge of a plateau.

FIXED POINT:

Used in making a map to denote a point that has been fixed on the paper by survey methods.

GORGE: 

A narrow stream passage between steep rocky hills; a ravine with precipitous sides.

GRADIENT: 

A slope described by a percentage, mostly used on roads to indicate the rise and fall in a road; e.g., a steep hill.

GRATICULE:

Lines of longitude and latitude drawn on a map as the basis for a system of map references.

GRID:

Lines drawn on the map forming squares as a basis for a system of map references.

GRID NORTH: 

Except through the origin, grid lines do not lie true north and south or east and west. Grid North is the direction of the north-south grid lines on a map.

HACHURES: 

A conventional method of showing hill features by shading in short lines drawn in the direction of the slope. thicker at the top of the slope than at the bottom.

HORIZONTAL EQUIVALENT (HE): 

The horizontal distance on the ground between two adjacent contours

ISOGONAL: 

A line drawn on a map through places having the same magnetic variation.

KNOLL: 

A small knob like hill.

LEFT or RIGHT BANK:

The appropriate bank of a stream or river when facing DOWN stream.

LOCAL MAGNETIC ATTRACTION:

Attraction of the compass needle due to presence of metal or magnetic iron ore. NOT to be confused with Magnetic Variation.

LUBBER LINE:

Sometimes referred to as the HAIR LINE running through the glass lid of the Prismatic Compass, used for sighting on an object when taking a bearing.

MAGNETIC VARIATION or DECLINATION:

The angle between True North and Magnetic North.

MAGNETIC NORTH:

The point in far north of Canada, to which a compass needle points.

MERIDIAN: 

A true north and south line.

ORIENTING a MAP:

Placing it so that its True North line points True North (or Magnetic or Grid North line points to Magnetic or Grid North). This is also called “Setting the Map”.

PLATEAU: 

A table land: A raised plain, usually quite flat, above a level of the land.

PLOTTING: 

Transferring to a map bearings and other measurements.

RAY: 

A line drawn from the position of an observer to fix the direction of an object.

RAVINE: 

A long deep valley worn by a stream

RE-ENTRANT:

A shallow valley or ravine, usually between two spurs, running inwards towards the hill or mountain top. Usually found where a stream runs off a hillside.

RIDGE:

The line along a hill or range of hills or mountains from which water flows in opposite directions; a divide; sometimes the crest of a line of hills as it appears along the horizon.

RESECTION:

The process of finding a position by taking bearings on two identifiable points and plotting them on a map, also by fixing a position by observation of at least two previously identified points.

SADDLE:

A depression between adjacent hill or mountain tops: also called a col.

SECTION: 

A line drawn to represent the shape of the surface of the ground along a line between two points.

SPOT HEIGHT:

A point on a map whose height has been found by survey methods, identified by a dot with figure against it.

SLOPES:

(Concave and Convex): Convex “bulges out”, Concave “caves in”.

SPUR:

A hill feature or low ridge, running out from a hill or high ground, often found between two re-entrants.

TRIG POINT:

A concrete pillar with a brass mounting used by Ordnance Survey for their survey work.  The correct name is a Triangulation Point. Marked on a map by a small triangle with the height above sea level shown next to it.

TRUE NORTH:

The direction of the North pole from that point.

VERTICAL INTERVAL (V.I.): 

The difference in level between two adjacent contours on a map.

WATERSHED:

The line, usually mountain range where waters divide to flow into different river systems; the edge of a river basin.  

GLOBAL POSITIONING SYSTEMS (GPS)

Global Positioning System is a small, battery-powered, handheld receiver, that helps you locate yourself on the ground, by picking up signals from satellites in stationary orbit around the earth.

Each model and there are lots of them, has different features so we can’t teach you how to use it, but they come with easy to understand instructions, so instead here are a few tips. GPS is a “War winning bit of kit” a senior officer was heard to say during the First Gulf War.

The ability to give you an accurate grid reference wherever you are in the world has obvious advantages when you’re out and about.

However, nothing is 100% reliable and you should bear in mind a few things when using it. The batteries run down and do so quickly with constant use, depending on the model you’re using, so make sure you’ve got a fresh set of batts on you when you start and take some spares.

Try to ensure they’re the same type as other battery-powered things you’re carrying, this will save weight as you won’t have to double up. Get it out and use it, it’s an incredible bit of kit, but you need to dedicate a few hours to really finding out what it can do, have a play with it. The displays can crack with rough treatment so take care of it, if it’s on your pocket you can wrap it in your gloves or a woolly hat.

GPS relies on a clear view of the sky to give you a triangulated position, so make sure you are not standing next to a large building, in a basement, or at the bottom of a cliff, in a street with not much view of the sky, because if the unit can’t see at least three satellites you won’t get a really pinpoint position.

Bear this in mind when you are in woods, forest or in the jungle, you will have problems, as the unit might not able to see the sky (Remember those 6 P's)

Prior, Preparation, Prevents, Pretty, Poor, Performance.

Reliance on GPS may mean that you neglect your map reading, so if the unit goes down, you might be up to your neck in it, use GPS as a check nav and for confirmation, but always keep on top of your map reading with compass and map, or at the very least, ensure you have the correct mapping and know where you are so you can sort yourself out with your map. Always reboot/turn on your GPS before you set off, so that it can get its bearings, especially if you have travelled across borders, the unit might be confused and crash.

Don’t wait till you need it urgently to switch it on and find that it’s not working

As with anything in life,  rely on it but not too much!