What is the Ordnance Survey National Grid?
Q: What is the Ordnance Survey National Grid?
A: The Ordnance Survey National Grid is a system used to map Great Britain. It was created by the Ordnance Survey (OS) and is different from using latitude and longitude.
Q: How does the system divide the map?
A: The system divides the map into squares, with each square labelled with two letters. The first letter refers to squares that are 500 km by 500 km, while for the second letter each 500 km square is divided into 25 squares that are 100 km by 100 km.
Q: How can locations be specified within a lettered square?
A: Locations within a lettered square can be specified by giving the distance east and north from the southwest corner of the square. For example, NH0325 (or NH 03 25) means a one-kilometre square whose southwest corner is 3 km east and 25 km north from the southwest corner of square NH.
Q: What are some of these large squares outlined in dark grey on maps?
A: These large squares outlined in dark grey on maps include S, T, N and H - only four of these have a lot of land area in Great Britain. The O square contains a tiny area of North Yorkshire which normally most of this area is submerged at high tide.
Q: How do you label smaller areas inside a lettered square?
A: Smaller areas inside a lettered square can be labelled by giving their grid reference which specifies their distance east and north from its southwest corner. For example, NN 166 712 gives the location of Ben Nevis' summit which lies in an area smaller than one kilometre squared.
Q: What letters are used to label each 100km x 100km section?
A: Each 100km x 100km section has its own letter code ranging from A to Z (excluding I). Letters start with A in northwest corner and go to Z in southeast corner.
Q: Is there an example given for how this works?
A: Yes - NH0325 (or NH 03 25) means a one-kilometre square whose southwest corner is 3 km east and 25 km north from the southwest corner of Square NH
