All the longitude lines are equal in length and run from one pole to the other and all latitudes are parallel, creating a grid that is called graticule (a spherical grid). For most GCSs this Greenwich line.Ĭorresponding to the prime meridian is the equator – the widest part of the planet when it is observed from north to south.Ĭoordinates – Longitude and latitude representing the angle of the point with respect to the core. Prime meridian – the agreed “0,0” longitude for the GCS. I know that all sounds complicated, but I’ll try and break it down. Each point is measured from the core of the planet and has 3 parts: coordinates (angular measure from the core), a prime meridian and a datum. GCS doesn’t actually measure the surface of the planet, but the whole spherecal shape of it.
The GCS is a very complicated system to calculate the exact location of a point on the planet. There many coordinate systems used on Earth, but I will discuss the two main ones: GCS and UTM. Think about the planet as an orange being scored for “easy peeling” – you make straight strips that are closer at the top and bottom but wider apart at the circumference. The reason that we need to think about coordinate systems as wedges and not plain grid system is the fact that earth is a ball, and a square grid won’t work due to the curvature. Coordinate SystemsĬoordinate systems are a way to “cut” the planet to wedges – both horizontal ones an d vertical ones – in order to give each location that grid “address” that I mentioned above. Also this is as complicated as it will get here in this series, to try to stick it out – it will get easier after this, I promise! In the next few paragraphs I will try to explain it, but if you feel that you lose me, just stop, have a break and come back to it. There is actually a whole scientific field called geodesy just on coordinate systems, so it can be a huge subject. Now this subject can be really, really complicated. Grid maps are inherently very simple and they usually use a cartesian system (X,Y system) that gives a point an X address and a Y address, resulting in an X,Y point.Ī grid system is only good if it can be used to describe that address universally, and for that we have coordinate systems. The purpose of the grid system is to give each point in the map an identifier, an address, by which we can refer to it by.
If this is the first time you are joining the Map Reading series, you should start from the first post.Ī grid system on a map is usually square and is represented by drawn lines on the map creating those squares.
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