The capacity to learn a map is a type of survival abilities that more and more is changing into misplaced in an ocean of expertise. While map and compass navigation takes some data and is a perishable talent, the act of studying and understanding a map is fairly easy.
Once what you’re looking at, and the way to use that info, you can begin to acknowledge the connection between map and the terrain.
For this text, I will probably be discussing topographic maps, however the fundamental principals outlined right here can be utilized to learn and navigate with nearly any map. This article can also be particularly geared to the studying of a map and assumes that you’re already proficient within the operation of a compass and GPS unit.
Key Information
There are just a few key items of knowledge which are listed on any topographic map. Magnetic declination, coordinate techniques, map datum, legend, and scale are all items of knowledge that it’s best to pay attention to when studying a map.
Make positive to learn our article on what kind of maps to keep with you…
Magnetic Declination
The location of the North on a map just isn’t so simple as it will appear. There are three separate ‘Norths’ on a topographic map that are:
- True North, which is on the prime of the map.
- Grid North, which is what place the UTM grid traces level to
- Magnetic North, which is what place your compass needle is pointing
Earth’s Magnetic North Pole is offset from True North and Grid North and this offset is named magnetic declination.
Earth’s magnetic pole additionally maneuvers over time and this motion must be accounted for.
On a topographic map, there must be a magnetic declination diagram that can let you know the angle and path of offset between True North, Grid North, and Magnetic North. In numerous circumstances, the distinction between True North and Grid North is just too small to be adjusted for on a typical compass to allow them to be used interchangeably.
This diagram will show the levels and path of declination that existed in the course of the yr the map was printed. Using this info you’ll be able to calculate what the present yr’s declination is. Another choice is to search for the magnetic declination in your map’s space utilizing Google.
One necessary level of notice is that the speed and path through which declination modifications which are written in your map is an estimate made on the time the map was printed. If your map is a number of a long time outdated one can find that by determining this yr’s declination mathematically the consequence will typically be completely different than what the true magnetic declination is. It is necessary to have the freshest info when adjusting your compass in your space’s magnetic declination.
If you may have a compass that has adjustable declination you’ll want to dial the present yr’s declination into it so you should utilize a compass along with your map. If your compass doesn’t have adjustable declination then you’ll have to add or subtract the diploma of declination each time you plot bearings.
Coordinate Systems
To establish a selected level on a map we use coordinates. These coordinates could be Latitude and Longitude or the Universal Transverse Mercator (UTM) system. There can also be the Military Grid Reference System MGRS which makes use of the identical grid traces because the UTM system with some minor variations.
Latitude and longitude is the coordinate system most of us have at the very least some familiarity with. Latitude and longitude coordinates are expressed as both Degree, Minutes, and Seconds (DMS) or Degree Decimals.
For instance:
In levels, minutes, and seconds.
- 37 Degrees 14’ 35” North Latitude by 115 Degrees 47’ 34” West Longitude.
Or in diploma decimal.
Latitude and Longitude coordinates have a disadvantage of not being fast or intuitive to plot or navigate through the use of a map and a compass. In a survival scenario, it’s sooner, simpler, and extra exact to make use of both the UTM or the MGRS
UTM and MGRS Coordinates
UTM and MGRS coordinates use a grid of 1000m by 1000m squares to plot coordinates. This gives two distinct benefits over latitude and longitude. First is that plotting coordinates could be accomplished in a short time utilizing the UTM scale on the clear baseplate of an excellent compass. The second is that since these grid squares are 1000m by 1000m it’s fast and simple to estimate distances on the map by counting grid squares.
An instance of a UTM grid coordinate
And an MGRS coordinate
The first two numbers and letters are the UTM grid zone. The world is split into 60 grid zones every of those zones is split once more south to north into horizontal bands which are lettered from South to North with the letters C to X.
After the grid zone designator the primary set of numbers is what is named the Easting as a result of we learn the coordinates from west to east. The Easting grid traces are numbered by designating the middle Easting line as 500,000m.
The second set of numbers is the Northing. These are the horizontal grid traces which are numbered acceding from the equator which is 0. To keep away from damaging numbers the southern hemisphere designated the equator as 10,000,000m North. The Northing of the UTM coordinate is basically the space in meters from the equator.
The MGRS divides the UTM grid zone into 100,000m by 100,000m squares that are designated with a two letter designator. Because of this, the MGRS designates every grid sq. with a pair of two-digit numbers as an alternative of a distance in meters from the central meridian and the equator. This provides you much less digits to interpret and makes plotting coordinates sooner.
Map Datum
The coordinate system on a map has an outlined level that it’s primarily based off. This level is named a datum and your map ought to have the datum used indicated on the map. Knowing your map’s datum is necessary as a result of except you program the right datum into your GPS unit you’ll not be navigating with correct coordinates. This additionally issues if you’re attempting to link up with different folks by giving them a set of coordinates. If you don’t additionally point out your datum it’s potential to finish up a number of hundred meters aside.
Legend
The legend on a map will let you know what every image used on the map means. This info is necessary as a result of a topographic map has numerous traces, symbols, and grids which could be complicated and not using a legend to interpret them. Knowing how the several types of roads, waterways, buildings, or borders are drawn on the map is crucial to learn a map correctly.
Scale
Topographic maps are drawn to scale which is represented by a consultant fraction or a ratio comparable to 1/50,000 or 1:50,000. This means one unit of measurement on the map represents 50,000 of that unit of measurement on the bottom. For instance, a scale of 1:50,000 means 1 inch on the map equals 50,000 inches on the bottom.
This additionally implies that the upper the quantity (for instance 1:250,000) the better floor space the map covers however with far much less element, whereas the decrease the quantity (for instance 1:10,000) the map will cowl much less floor space however in better element.
A map must also have a scale drawn on the map that provides you a ruler that visually reveals you what a mile or kilometer appears to be like like on the map. You can use this to find out distances on the map through the use of a ruler, string, or some folded paper.
Reading the map
Once and perceive all the important thing info that your topographic map is attempting to indicate you it’s time to begin studying the map.
Orientating
Every time you pull your map out you’ll want to orient it to the bottom. What this implies is that you just maintain the map in order that the highest of the map points to True North.
How you do that is you are taking your compass, which ought to have adjustable declination, and the right declination dialed in, and line up the sting of the compass with the sting of the map.
Make positive that the bezel on the compass is dialed to level North. Rotate the map till the needle of the compass sits contained in the declination arrow (which is named crimson within the mattress). Once you do that the map is oriented to the bottom which makes navigation with it less complicated.
Understanding contour traces
One of the important thing options of a topographic map is the contour traces that are a approach to visually show modifications in terrain. A contour line is brown and represents a line of steady elevation above sea degree. For instance, if a contour line says it’s 500 meters above sea degree then any level alongside that line will probably be 500 meters in elevation. A topographic map can even have one thing known as a contour interval which is the distinction in elevation between the contour traces.
Since contour traces are representing elevation, the nearer the traces are collectively the steeper the terrain, and the extra spaced out they’re the extra gradual the slope.
Some contour traces are drawn thicker and have an elevation written into them. These are often called index traces and are there to tell you what the elevation of that contour line is so you’ll be able to decide the elevation of the adjoining traces utilizing the contour interval as a reference.
Plotting Coordinates
Latitude and longitude
Each corner of the map could have its latitude and longitude indicated and the perimeters of the map space are divided up into minutes of latitude and longitude. To plot latitude and longitude coordinate set, you’ll must challenge the marks alongside the sting of the map to the purpose you want to plot.
Plotting latitude and longitude is by no means environment friendly and takes time, observe, and talent to do precisely which I can’t cowl right here as a result of a greater system, particularly for survival, is the UTM or MGRS.
Plotting a UTM or MGRS Coordinate
We understand how a UTM and MGRS coordinates break down however how can we plot them on a map?
The course of is identical for each UTM and MGRS coordinates.
- Find the grid sq. that the purpose you wish to plot is situated in.
- Starting with the Easting, decide what the variety of the Easting line for this grid sq. is.
- Then decide the Northing grid line quantity.
- Using a UTM scale on a compass or roamer plot what number of meters the purpose is from Easting after which the Northing.
- This provides you your full grid coordinate.
An straightforward approach to keep in mind the way to plot coordinates is the phrase ‘in the door up the stairs’. If you image the map as a home you’ll stroll left to proper (West to East) to go ‘through the door’, then go up (North) which might be the ‘up the stairs’.
Terrain Association
As you utilize a map put within the wilderness you’ll start to mentally affiliate the contour traces on the map with the terrain in actual life. As you begin to kind this capacity you can begin to forgo utilizing a compass whereas navigating through the use of the strategy of terrain affiliation.
It is finest when you have an excellent vantage level with a view of the encircling terrain. As you maintain the map search for and see should you can match terrain options which you can see in entrance of you with options on the map. You can search for peaks, valleys, saddles, rivers, ridgelines, and so on, after which discover them in your map. You can then use this info to infer your location and to orient the map to the bottom.
When what place you might be you’ll be able to plot a route that follows terrain options as an alternative of utilizing compass bearings or a GPS.
For instance, you possibly can comply with rivers, valleys, ridgelines, roads, powerlines, and so on to maneuver in the direction of your goal as an alternative of lifeless reckoning cross nation.
Terrain affiliation works effectively too when you find yourself on the transfer and may hold monitor of a number of landmarks to help you in holding your self on the best path.
Wrap Up
This has been a really fundamental break down on the way to learn a map in a survival scenario. The matter of land navigation may be very broad and whole books have been written on the topic. Before heading afield make it possible for your understanding and talent in land navigation are updated and effectively practised.