How big is an Ordnance Survey grid reference?
100 metres square
All OS maps are criss-crossed by vertical and horizontal grid lines (coloured blue on OS Explorer maps) which are 4cm apart on 1:25,000 scale maps and 2cm apart on the 1:50,000 scale. A grid reference uses six figures to identify a particular spot on a map that is 100 metres square.
What is the distance between grid lines on an Ordnance Survey map?
1km
Remember that the grid lines on a 1:25 000 scale map are 1km apart. A quick way of estimating distance is to count each square you cross in a straight line.
Are Eastings horizontal?
The vertical lines are called eastings. They are numbered – the numbers increase to the east. The horizontal lines are called northings as the numbers increase in an northerly direction.
Where can I download the Ordnance survey grids?
From 29 January 2021, you can download a GeoPackage containing these grids at a number of resolutions (1, 5, 10, 20, 50, and 100 km) from Ordnance Survey’s GitHub: https://github.com/OrdnanceSurvey/OS-British-National-Grids. a tool that can create an OS grid at a specified resolution? The following plugin for QGIS does the job nicely:
Where can I find a 1 km grid?
Ordnance Survey’s GitHub organisation now has a repository containing a GeoPackage of these grids at various resolutions (including 1 km): https://github.com/OrdnanceSurvey/OS-British-National-Grids. Thanks for contributing an answer to Geographic Information Systems Stack Exchange! Please be sure to answer the question.
How many tetrads are in a 10 km grid?
A tetrad (from the Greek tetras meaning four) on the other hand is a collection of four 1-km squares arranged into a 2 km by 2 km square. There are 25 tetrads within each 10-km square and these are labelled A to Z, excluding O (to avoid confusion with zero), from bottom left (SW) to top right (NE).
What was the purpose of the Ordnance Survey?
In 1791 the Ordnance Survey was founded as Britain’s national mapping organisation, mostly to produce maps for military purposes. In 1799 Ordnance Survey rose to the challenge of invasion from France and the entire OS staff were sent to the English south coast to survey the counties thought at most risk.