1000 metres to the east is outlined ninety, then ninety one, status for 390000 and 391000 metres. Figures persist with as much as ninety nine, then the following one is 00. The ‘99’ stands after all for 399000m, and because the main sq. divisions of the OS grid are 100km (100,000m), which means now we have reached the tip of 1 (it’s really ST) and the start of one other (SU). The ‘00’ figure accordingly really stands for 400000m. Going extra east alongside the sting of the map, the figures proceed to increment: 01, 02, 03, and so on. , until eventually we succeed in 19, the road marking the west part of the sq. containing Fussell’s inn barrow. This line, then, is 419000m east of the grid foundation. in a similar fashion, it may be demonstrated that the road at the south aspect of the barrow’s sq. is 132000m north of the starting place. we will be able to now upload the expected figures to every a part of the grid reference, to offer 419100m east and 132500m north. The conference of quoting references within the shape SU 191 325 can store house, however it includes utilizing numbers in a marginally unusual method. be aware additionally that during a basically numerical shape either easting and northing result in ‘00’ – they're right to the closest 100m, this means that this grid reference defines a 100m sq., and each aspect inside that sq. could have an analogous SU 191 325 reference, even though if we had a larger-scale map shall we provide an extended reference, that could define a 10m (eight-figure), or perhaps 1m (ten-figure) sq. (or come to that zero. 1m or zero. 01m). many folks analyzing this can believe that the purpose is being laboured, and that everybody studying this booklet will already be acquainted with the data. My excuse is that i'm drawing awareness to the complexity of whatever that's so widely used that the majority of the time we don’t take into consideration what it capacity. the complete sector coated through the OS nationwide Grid is 700,000m by way of 1,300,000m, and this grid is conceived of as a aircraft. handy in lots of methods, because it makes it effortless to define the relative positions of issues at the floor when it comes to ‘metres east and metres north’, yet in fact the skin of the Earth isn’t flat, and whereas we will forget about this truth over distances of even numerous thousand metres, it can’t be overlooked over the full OS grid region. How does this flat airplane relate to the curved floor which really exists? Surveying on a world scale seventy nine Going again to the map sheet, there are a few extra figures published alongside the perimeters, corresponding to ‘Lat 51°N’ and ‘Long 1°35’W’. those check with one other co-ordinate approach altogether, and are what are referred to as ‘geographic co-ordinates’. they're after all the worldwide co-ordinate method of range and longitude, measured in levels north or south of the equator and east or west of an arbitrary line of longitude which for historic purposes is one passing via Greenwich in south-east England. The notional place from which those levels are measured is the centre of the earth. Going from a place at the earth’s curved floor to a flat airplane includes a mathematical approach referred to as ‘projection’. Imagined easily, this implies devising a form which are made to fit around the earth (a cylinder, for instance, that is utilized by the Ordnance Survey), and onto which issues from the curved floor may be drawn.