Land Navigation and Map Reading

The military grid system is a network of squares formsd by north-south and east-west grid lines placed on a map. The numbers along the gridlines are the grid coordinates. Depending on the zoom level, the each gridline will have 1, 2 or 3 digits on it.
The distance between single-digit grid lines is 10km, between double-digit grid lines is 1km and between 3-digit grid lines is 100m.
Grid squares are identified by the grid lines that create its southern and western borders. I.e. a grid square with grid line 34 along its west border and 61 along its south border would be grid square 3461. The area of a grid square would be the square of the distance between the grid lines.
To increase accuracy of a measurement, divide a grid square into 10 imaginary sections and add the value of the section onto the coordinates. I.e. a location in the north-western section of grid square 3461 could have the coordinates 343618.
6 digit grid coordinates are most commonly used, although 8 digit grids are recommended for SALUTE reports and calling in air support or indirect fire.

Azimuths are measurements of direction. Azimuth measurements are measured clockwise from a north baseline. This imaginary clockface can be broken into 360 equal units called degrees. Degrees are numbered clockwise, with east at 90 degrees, south at 180 degrees, west at 270 degrees and north at 360 or 0.
Back azimuths differ from a normal azimuth by 180 degrees.

Terrain features are derived from a complex landmass known as a mountain or ridgeline. The term ridgeline is not interchangeable with the term ridge.
A ridgeline is a line of high ground, usually with changes in elevation along its top and low ground on all sides, from which a total of 10 natural and manmade features are classified.
Primary terrain features:
Hill- when you are on a hilltop, the ground slopes away in all directions.
Ridge- when you are on a ridge, the ground slopes away in 3 directions and up in 1.
Saddle- when you are in a saddle, there is high ground on 2 opposite sides, and low ground on the remaining 2.
Valley- when you are in a valley, there is generally level ground bordered on 3 sides by higher ground. Often has streams or rivers.
Depression- low point or hole in the ground with high ground on all sides.

Minor terrain features:
Draw- like a valley, but less developed. No level ground and little to no maneuver room.
Spur- short sloping line of higher ground jutting out from the side of a ridge. Usually forms the sides of a draw.
Cliff- a vertical or near vertical slope.

Supplementary terrain features:
Cut- manmade feature resulting from cutting into/through high ground.
Fill- manmade feature resulting from filling in a low area, usually to form a road or railroad bed.