Grid Reference Help!

[JetMouse]

Could someone please explain how grid references work?

I'm using the Southern England and Wales Edition 27
ICAO 1:500 000 chart and am having some difficulty pinpointing aerodromes...

For example I have a grid reference for Shoreham of N5050.03 E00017.57 - is this right? Surely it should be W00017.57?

As you can probably tell I'm quite confused, so if someone could explain how the grid references are broken down and how you can use them to quickly pinpoint an area, I would be very grateful!

Thanks
JM

[Evo7]

It's must be a misprint - it's West.

For Longitude, the first three digits are degrees East or West of the prime meridian, next two are minutes (60 minutes = 1 degree) and the last two are seconds (60 seconds = 1 minute).

So Shoreham is 0 degrees, 17 minutes and 57 seconds West of the Prime meridian.

With Latitude there are only two digits, as you can be a maximum of 90 degrees away from the equator. Hence Shoreham is 50 degrees, 50 minutes and 3 seconds North.

On the half-mil charts there are lines of longitude and lattitude marked every 30 minutes.

[Noggin]

Firstly you are refering to a Lattitude and Longitude, that is not the same as a Grid Reference.

A Grid Reference is based upon a square graticule placed on a map or chart. i.e. National Grid. The scale is linear and decimal in nature. Measurements move away from the origin.

Lat and Long is not linear and is initially based upon Degrees and Minutes of arc. The minutes may then be sub-divided into seconds(base 60), or alternatively into decimal parts of a minute (base10). Unfortunately they are often presented in a manner where it is difficult to determine which system is being used. Unlike a Grid, Lat Long measurements may move in either direction hence E/W and N/S

Shoreham is as you say West not East.