You can also add in the National Grid code, a 2 letter code which is in essence the name of your map, before the numbers for a full grid reference. These numbers together provide you with the grid reference for your chosen location. This will provide you with another number. You then work up the northings until you get to the lower left corner of the row of squares you are in. To get the grid reference of any given point of a map you first work left to right along the eastings until you reach the lower left corner of the column of squares you are in. Along these gridlines, at the bottom and side of the map, are numbers which allow you to get your grid references. The horizontal lines are read left to right and are called ‘eastings’ while the vertical lines are read bottom to top and are called ‘northings’. Gridlines are lines that run horizontally across and vertically up a map. These elements can help you navigate, calculate distance and assess the elevation of the terrain as you hike. Obviously the values are not directly equivalent, and some care should be taken in choosing the most appropriate format when reporting grid reference values.The basic elements of a map are made up of gridlines, contours and symbols. This places the working position of the origin a little to the south-west of Lands End and ensures that the co. In contrast the highest precision value ( SW 12000 12000) resolves the point with a precision of 1m by 1m. subtracted from all northing co-ordinates. 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. Which is the correct way to get a grid reference. When giving grid references which number should you give second A. When giving grid references which number should you give first northings. When reporting locations as OS grid references, the relevance of precision is often overlooked. Which scale shows the smallest area on a map and as a result the most detail: 1:50000 or 1:25000 eastings. 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) Many translated example sentences containing 'ordnance survey grid' Portuguese-English dictionary and search engine for Portuguese translations. 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: The Coordinate Transformation Tool transforms GNSS based ETRS89 latitude and longitude or cartesian XYZ coordinates to the equivalent OSGB36 National Grid eastings and northings, and vice-versa, using Ordnance Surveys National Grid Transformation OSTN15.
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