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A grid system top top a map is usually square and is represented by drawn lines top top the map producing those squares. The function of the grid system is to provide each suggest in the map one identifier, an address, whereby we have the right to refer to it by. Net maps are inherently very simple and they usually use a cartesian device (X,Y system) that offers a suggest an X address and a Y address, bring about an X,Y point.
A grid device is only an excellent if it have the right to be provided to describe that address universally, and also for that we have actually coordinate systems. Currently this subject deserve to be really, really complicated. There is actually a entirety scientific field called geodesy just on name: coordinates systems, therefore it have the right to be a vast subject. In the next few paragraphs ns will shot to explain it, yet if you feel the you shed me, simply stop, have a break and also come earlier to it. Additionally this is as complex as that will acquire here in this series, to shot to pole it the end – it will get easier after this, i promise!
Ok, lets dive right into it.
Coordinate systems space a method to “cut” the planet to wedges – both horizontal persons an
There countless coordinate systems supplied on Earth, yet I will comment on the two key ones: GCS and UTM.
Geographic Coordinate equipment (GCS)
The GCS is a very complicated system to calculate the specific location the a suggest on the planet. GCS doesn’t actually measure the surface of the planet, but the entirety spherecal shape of it. Each point is measured indigenous the main point of the planet and also has 3 parts: coordinates (angular measure up from the core), a element meridian and also a datum. I recognize that every sounds complicated, yet I’ll try and rest it down. Lets start through the prime meridian:
Prime meridian – the agreed “0,0” longitude for the GCS. For many GCSs this Greenwich line.
Corresponding come the element meridian is the equator – the widest component of the planet when it is it was observed from phibìc to south.
Coordinates – Longitude and latitude representing the angle of the allude with respect to the core. All the longitude lines room equal in length and also run from one pole to the other and also all latitudes are parallel, producing a grid that is called graticule (a spherical grid). Works with are represented by decimal levels or by a levels (°), minutes (‘), secs (“) (DMS) system. Longitudes run from 180° (when travel west from prime meridian) to -180° (traveling east). Latitudes range from 90° (north come the equator) come -90° (south).
To get specific locations (each square that is developed by a longitude and a latitude is nice big), the level system is have the right to be broken down to smaller increments. For example: 51.501019° N, -0.093728° W (My favourite pub) in decimal degrees. The DMS device uses the minutes and also seconds rather of the increments, such that each degree has 60 minutes, and also each minute has actually 60 secs (so each level has 3600 seconds…). That method that the same coordinates above will it is in 51° 30′ 3.6684” N, 0° 5’ 37.4208” W (still my favourite), together you can see it is DD MM SS system.
I hope that is clear sufficient that from now on you have the right to look at a collection of coordinates and know what they mean. GPSs use the decimal degree system to give a reading, for this reason knowing how to watch at works with is important.
Datum – these are an extremely tricky since they are here to carry out nothing yet confuse things more (that is just how I feeling at least). First, the is necessary to recognize there are numerous GCS systems being used roughly the world; lock all around similar, yet not precisely – they might vary by as much as 200m (218 yards) from point to point. That way that the exact same coordinates, used on maps that show various GCS will result in an as much as 200m error. If friend think this is not appropriate for you, move on, if the is, remain with me for a little longer.
Datum way a single data (just for your knowledge) and also in geodesy (science that mapping) it method the shape and also size of earth. There are hundreds of data, as various measurements have actually been make to planet (starting in the 1700s), but for mapping us are just going to focus on horizontal datum (on the surface). The datum is a reference point for the GCS grid to “place” the longitude and also latitude lines). The one most frequently used is the WGS84 (World Geodetic System, updated at 1984), while in the USA friend can find NAD83 (North American Datum 1983) and in the UK, OSGB36 (Ordinance inspection of an excellent Britain 1936). All 3 GCSs are really similar, so not much of a trouble there.
The data are just a reference suggest to save an eye on if you are in a less surveyed area.
From all this you deserve to see that the GCS is a very complex system, for this reason luckily because that us, many of the mapping ~ above the planet moved to a much much easier system, UTM:
Universal Transverse Mercator (UTM)
The UTM mechanism is based upon a basic concept the meractor projection: ‘pseudocylindrical’ conformal forecast (big words for preserving that shape). The UTM is a estimate of earth’s sphere using the poles to produce a level representation of the sphere, meaning, the maps you view everywhere. This is done by swathing (creating over-lapping layers) – areas about the equator room over-lapped, causing zone boundaries overlapping in some places. This is supplied in stimulate to stop curvature in the longitude strips of every zone (which would make it difficult to present on a flat map!).
By producing a level representation, the human being can be split into rectangles (called UTM zones) that are basic to find and also use top top maps. Every UTM zone is 6° vast (so there room 60 zones) and it starts at 180° in the GCS mechanism (so the mid the zone 30 is on the Greenwich line). ~ the break because that the 60 zones, we divide each ar to 2 parts: east and also west, with a line referred to as the central meridian – this is the only line in each zone that is no distorted in ~ all due to the projection. This line is offered to align the zones. It is necessary to understand that because of the swathing that happens about the equator, the zones are not actually equal in length throughout the zone. They space much broader around the equator as they are close to the poles (due to Earth’s curvature).
Latitude is damaged into 20 strips (C to X, A+B and also Y+Z represent the poles) through the equator separating it right into 2 parts: northern and also southern. Those room not component of the UTM but the MGRS however are quiet used.
The tricky little is to actually gain a place in the UTM system. First, the is vital to understand that the UTM is a meteric system, and can actually give a ar down come the meter. Second, we have to look at each location as being a certain distance eastern (easting) come the main meridian line of the zone, and certain distance north (northing) come the equator. On the contrary side, south and west have the right to be negative numbers, but we don’t like an unfavorable distances, therefore a “falsing” cheat is implemented: If any suggest is south to the equator, that is measured north to the south pole. If a allude is west come the meridian line, it is measured from a false line 500km west to the central meridian (false easting). I recognize this sounds an extremely tricky, however I’ll try to explain.
I think the north/south separation is simple. It method that a point in the north hemisphere deserve to be a best of 9,300,000m and in the south 10,000,000m.
The east/west separation is also basic if us look at every zone as simply one component – eastern only. For simplicity, the west line is relocated 500,000m so that there is only one direction to attend to (false easting).
So, back to mine pub – it is in zone 30 (most that England), 5,709,547m phibìc (of the equator), 701,708m eastern (from the false easting).
That is it for UTM, i hope you got that, together it is an extremely tricky however the an ext you use it, the simpler it becomes.
A pair more points
Just a suggest to mention – along this lines, there are the USA quadrangle maps that usage 7.5 minute grid (unlike the 60 minutes device in the GSC) , the OS national grid (UK) that uses Transverse Mercator Projection like the UTM but only because that the UK, and many others.
It is necessary to check which grid system your map is using, particularly if merged with a gps device.
Way to walk for do it come the end! that was not basic one, and I hope you made the in one piece all the way here. As I said, it will get easier from here. Works with systems only become relevant when interacting a location to some one else, prefer emergency services. Being able to use the collaborates your map gives is important, just like having a first aid kit – when things go wrong. That is simple to disregard this knowledge and let the rust, but shot and offer yourself a refresher every so regularly so remain “in shape”.
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If friend still have questions around this, just send me an e-mail or comment below and also I’ll try to describe more.
Check the end the previous part – What space true north, magnetic north and also grid north