NY 215 072) which indicates the same location on the ground but is only accurate to 100 metres. Traditional OS Coordinates consist of two letters and a 6 figure number (e.g. NY 21538 07204) indicates a location on the ground that is accurate to 1 metre. The Two Letter and 10 Figure OS Coordinates on our walks (e.g. I have downloaded one of your route maps and can only see 10 reference coordinates, I wonder if you provide 6 figure OS coordinates for the walks?Ī. Obviously the values are not directly equivalent, and some care should be taken in choosing the most appropriate format when reporting grid reference values.OS Map Coordinates - converting 10 figure GPS Coordinates to 6 figure OS Coordinates In contrast the highest precision value ( SW 12000 12000) resolves the point with a precision of 1m by 1m. precision) with which they identify the location.Īt the extreme ends of the scale, the lowest precision value ( SW 12 12) refers to a 1km by 1km square surrounding the relevant point (see Table 1 above). freely interchangeable)?Īlthough the four grid references refer to the same point, their format additionally indicates the confidence (ie. The number of figures that used in the grid reference convey important information about the precision with which the location is specified.įor example, consider the following grid references - are they all equivalent (ie. When reporting locations as OS grid references, the relevance of precision is often overlooked. Ultra-high precision generally exceeds everyday requirements. High precision format sometimes useful for static species of particular interest. Most widespread format suitable for many uses. Low resolution often sufficient for highly mobile species (eg. Applications of OS Grid reference values: However grid references can be specified to other levels of precision for example, many GPS units and online mapping resources provide 8-figure or 10-figure OS grid references as standard. This level of precision resolves to a 100m-square on the ground, which is adequate for most applications. OS grid references are most usually given in six-figure format (eg. 10ths of each 1000th)Īdditional horizontal/vertical offset in units of 1/100000 of a grid-square (ie. 10ths of each 100th)Īdditional horizontal/vertical offset in units of 1/10000 of a grid-square (ie. 10ths of each 10th)Īdditional horizontal/vertical offset in units of 1/1000 of a grid-square (ie. Primary horizontal/vertical offset in units of 1/10 grid-square sideĪdditional horizontal/vertical offset in units of 1/100 of a grid-square (ie. OS Grid reference values - precision associated with successive digits SW 726 182) is probably the most widespread and suited to many requirements. The Grid reference may include spaces between the separate parts, or may be written as a continuous string (depending on preference).Īs a result there is no single 'correct' way of writing a grid reference, although the 6-figure grid reference (eg. The number of digits (eastings+northings) can vary in length (generally between 4 and 10 digits) The 'eastings' value always has the same number of figures as the 'northings' value.īut some parts of the Grid reference are flexible, to allow them to be used in different ways: The Grid square identifier always consists of exactly two-letters Some parts of the Grid reference layout are always the same: Understanding a Grid Reference The three parts of a Grid Referenceīefore working with grid references, it is important to understand their format and be able to separate out the 3 parts that they contain:
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