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Land Navigation

Post by Saul2012 on Tue Aug 21, 2012 7:55 pm

Figured I'd post some helpful information for you all to help out with land navigation in the even you are missing items like a compass, watch, map, gps, etc. Knowing where you are and where you are going is key but when you don't have the tools necessary to figure it all out, then what can you do.

Arma and Operation flashpoint use the US military grid reference system or MGRS. These are topographical maps with a number coordinate system. Below I'm going to list out much of the key information on how to read a MGRS map (minor changes based on the arma setup), key terrain features, and so on in a kind of question format.

What are the basic colors of a map, and what does each color represent?
Black - Indicates cultural (man-made) features such as buildings and roads, surveyed spot elevations, and all labels.
Red-Brown - The colors red and brown are combined to identify cultural features, all relief features, non-surveyed spot elevations, and elevation, such as contour lines on red-light readable maps.
Blue - Identifies hydrography or water features such as lakes, swamps, rivers, and drainage.
Green - Identifies vegetation with military significance, such as woods, orchards, and vineyards.
Brown - Identifies all relief features and elevation, such as contours on older edition maps, and cultivated land on red-light readable maps.
Red - Classifies cultural features, such as populated areas, main roads, and boundaries, on older maps.
Other - Occasionally other colors may be used to show special information. These are indicated in the marginal information as a rule.
*Yellow - Identifies major roads.

What are contour lines?
Imaginary lines on the ground connecting equal elevation, they represent high and low ground elevation.

What are 3 types of contour lines?
Index
Intermediate
Supplementary

How many scales are there on a compass, what are they?
There are two:
Degrees
Mils

On a lensatic compass there are two rings, an outer black ring and an inner red ring, what are they used for?
The inner red ring is used to find degrees, and the outer black ring is used to find mils

How many Mils are in one Degree?
17.7 mils

What are 5 major terrain features found on a map?
Hill
Ridge
Valley
Saddle
Depression

What are the 3 minor terrain features found on a military map?
Draw
Spur
Cliff

What are the 2 supplementary terrain features found on a military map?
Cut
Fill

What shape are the contour lines that indicate a hill?

A hill is shown on a map by contour lines forming concentric circles. The inside of the smallest closed circle is the hilltop.

What shape are the contour lines that indicate a saddle?

A saddle is normally represented as an hourglass

What shape are the contour lines that indicate a valley?

Contour lines forming a valley are either U-shaped or V-shaped.

What shape are the contour lines that indicate a Ridge?

Contour lines forming a ridge tend to be U-shaped or V-shaped. The closed end of the contour line points away from high ground.

What shape are the contour lines that indicate a depression?

Usually only depressions that are equal to or greater than the contour interval will be shown. On maps, depressions are represented by closed contour lines that have tick marks pointing toward low ground.

What shape are the contour lines that indicate a draw?

The contour lines depicting a draw are U-shaped or V-shaped, pointing toward high ground.

What shape are the contour lines that indicate a spur?

Contour lines on a map depict a spur with the U or V pointing away from high ground.

What shape are the contour lines that indicate a cliff?

Cliffs are also shown by contour lines very close together and, in some instances, touching each other.

What shape are the contour lines that indicate a cut?
This contour line extends the length of the cut and has tick marks that extend from the cut line to the roadbed, if the map scale permits this level of detail.

What shape are the contour lines that indicate a fill?
This contour line extends the length of the filled area and has tick marks that point toward lower ground. If the map scale permits, the length of the fill tick marks are drawn to scale and extend from the base line of the fill symbol.

What is a benchmark?
A man-made marker showing points of elevation

What is the general rule for reading military grid coordinates?
Down and Left (on a true map it would be right and up, but their gps coordinates read backwords. Neutral )

What is a large-scale map?
Those maps with scales of 1:75,000 and larger are used for tactical, administrative, and logistical planning. These are the maps that you as a soldier or junior leader are most likely to encounter. The standard large-scale map is 1:50,000; however, many areas have been mapped at a scale of 1:25,000.

What does the term intersection mean?
Finding the location of an unknown point by sighting two or more known points

What does the term resection mean?
Resection is the method of locating one’s position on a map by determining the grid azimuth
to at least two well-defined locations that can be pinpointed on the map.

What are the three elements for a land navigation process known as Dead Reckoning?
Known starting point
Known distance
Known azimuth

Name 3 field expedient methods of determining direction?
The shadow-tip method, the watch method, and the North Star method

How close will an eight-digit grid get you to your point?
10 meters

How close will a six-digit grid coordinate get you to your point?
100 meters

Field-Expedient Methods of Determining Direction
Here are some ways of determining directions without specific tools. Most of these can be used effectively with the right kinds of models and such are available.

Shadow-Tip Method. This simple and accurate method of finding direction by the sun consists of four basic steps.



Determining Directions and Time by shadow

Step 1. Place a stick or branch into the ground at a level spot where a distinctive shadow will be cast. Mark the shadow tip with a stone, twig, or other means. This first shadow mark is always the west direction.

Step 2. Wait 10 to 15 minutes until the shadow tip moves a few inches. Mark the new position of the shadow tip in the same way as the first.

Step 3. Draw a straight line through the two marks to obtain an approximate eastwest line.

Step 4. Standing with the first mark (west) to your left, the other directions are simple; north is to the front, east is to the right, and south is behind you.

(1) A line drawn perpendicular to the east-west line at any point is the approximate north-south line. If you are uncertain which direction is east and which is west, observe this simple rule-the first shadow-tip mark is always in the west direction, everywhere on earth.

(2) The shadow-tip method can also be used as a shadow clock to find the approximate time of day.

(a) To find the time of day, move the stick to the intersection of the east-west line and the north-south line, and set it vertically in the ground. The west part of the east-west line indicates 0600 hours, and the east part is 1800 hours, anywhere on earth, because the basic rule always applies.

(b) The north-south line now becomes the noon line. The shadow of the stick is an hour hand in the shadow clock, and with it you can estimate the time using the noon line and the 6 o'clock line as your guides. Depending on your location and the season, the shadow may move either clockwise or counterclockwise, but this does not alter your manner of reading the shadow clock.

(c) The shadow clock is not a timepiece in the ordinary sense. It makes every day 12 unequal hours long, and always reads 0600 hours at sunrise and 1800 hours at sunset. The shadow clock time is closest to conventional clock time at midday, but the spacing of the other hours compared to conventional time varies somewhat with the locality and the date. However, it does provide a satisfactory means of telling time in the absence of properly set watches.

(d) The shadow-tip system is not intended for use in polar regions, which the Department of Defense defines as being above 60 degrees latitude in either hemisphere. Distressed persons in these areas are advised to stay in one place so that search/rescue teams can easily find them. The presence and location of all aircraft and ground parties in polar regions are reported to and checked regularly by governmental or other agencies, and any need for help becomes quickly known.





Watch Method. A watch can be used to determine the approximate true north and true south.

(1) In the north temperate zone only, the hour hand is pointed toward the sun. A south line can be found midway between the hour hand and 1200 hours, standard time. If on daylight savings time, the north-south line is found between the hour hand and 1300 hours. If there is any doubt as to which end of the line is north, remember that the sun is in the east before noon and in the west after noon.

(2) The watch may also be used to determine direction in the south temperate zone; however, the method is different. The 1200-hour dial is pointed toward the sun, and halfway between 1200 hours and the hour hand will be a north line. If on daylight savings time, the north line lies midway between the hour hand and 1300 hours



Determining Direction using a Watch.

(3) The watch method can be in error, especially in the lower latitudes, and may cause circling. To avoid this, make a shadow clock and set your watch to the time indicated. After traveling for an hour, take another shadow-clock reading. Reset your watch if necessary.



Star Method. Less than 60 of about 5,000 stars visible to the eye are used by navigators. The stars seen as we look up at the sky at night are not evenly scattered across the whole sky. Instead they are in groups called constellations.

(1) The constellations that we see depends partly on where we are located on the earth, the time of the year, and the time of the night. The night changes with the seasons because of the journey of the earth around the sun, and it also changes from hour to hour because the turning of the earth makes some constellations seem to travel in a circle. But there is one star that is in almost exactly the same place in the sky all night long every night. It is the North Star, also known as the Polar Star or Polaris.

(a) The North Star is less than 1 degree off true north and does not move from its place because the axis of the earth is pointed toward it. The North Star is in the group of stars called the Little Dipper. It is the last star in the handle of the dipper. There are two stars in the Big Dipper, which are a big help when trying to find the North Star. They are called the Pointers, and an imaginary line drawn through them five times their distance points to the North Star.

(b) Many stars are brighter than the North Star, but none is more important because of its location. However, the North Star can only be seen in the northern hemisphere so it cannot serve as a guide south of the equator. The farther one goes north, the higher the North Star is in the sky, and above latitude 70 degrees, it is too high in the sky to be useful.



Determining Direction by the North Star and Southern Cross

(2) Depending on the star selected for navigation, azimuth checks are necessary. A star near the north horizon serves for about half an hour. When moving south, azimuth checks should be made every 15 minutes. When traveling east or west, the difficulty of staying on azimuth is caused more by the likelihood of the star climbing too high in the sky or losing itself behind the western horizon than it is by the star changing direction angle. When this happens, it is necessary to change to another guide star. The Southern Cross is the main constellation used as a guide south of the equator, and the general directions for using north and south stars are reversed. When navigating using the stars as guides, the user must know the different constellation shapes and their locations throughout the world.



Constellations, Northern Hemisphere

Grid Coordinates

Finding your location on a map using grid coordinates
The map has vertical lines (top to bottom) and horizontal lines (left to right). These lines form small squares 1,000 meters on each side called grid squares.

The lines that form grid squares are numbered along the outside edge of the map picture. No two grid squares have the same number.

The precision of a point location is shown by the number of digits in the coordinates: the more digits, the more precise the location.

1996-a 1,000 meter grid square.
192961-to the nearest 100 meters.
19269614-to the nearest 10 meters

Look at Figure 1. Your address is grid square 1181. How do you know this? Start from the left and read right until you come to 11, the first half of your address. Then read up to 81, the other half. Your address is somewhere in grid square 1181.


NOTE:
Always begin your reading from the southwest corner (north east for arma based maps) of your square.



Grid square 1181 gives your general neighborhood, but there is a lot of ground inside that grid square. To make your address more accurate, just add another number to the first half and another number to the second half-so your address has six numbers instead of four.

To get those extra numbers, pretend that each grid square has ten lines inside it running north and south, and another 10 running east and west. This makes 100 smaller squares. You can estimate where these imaginary lines are.

Suppose you are halfway between grid line 11 and grid line 12. Then the next number is 5 and the first half of your address is 115. Now suppose you are also 3/10 of the way between grid line 81 and grid line 82. Then the second half of your address is 813. (If you were exactly on line 81, the second part would be 810). Your address is 115813 (B, Figure 5 18).

*** Note: Arma based maps read coordinates for Down and Left. This means that your first 2/3/4 digits will come from the top and your last 2/3/4 will come from the left sides of the map. They are essentially backwords but you can still gain your exact position on a map.
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Saul2012

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Re: Land Navigation

Post by msallstr on Wed Aug 22, 2012 1:23 am

My brain hurts after reading that.
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Re: Land Navigation

Post by Saul2012 on Wed Aug 22, 2012 2:14 am

At least I didn't go into length details or have to worry about Declination and the math accosiated with it Wink
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Re: Land Navigation

Post by msallstr on Wed Aug 22, 2012 2:16 am

Got no idea what your talking about but it seems... interesting
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