Streetmap funny
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There is a facility, coor_g.php, mainly used by Wikipedia, which takes an OS grid reference, converts it to latitude and longitude and links to a map sources page, thus: [http://toolserver.org/~rhaworth/os/coor_g.php?pagename=Beckingham_Palace¶ms=TL473132_region%3AGB_scale%3A25000 TL 473 132]. Streetmap.co.uk offers a facility to display the current location in a number of coordinate systems [http://streetmap.co.uk/idgc.srf?x=547350&y=213250 thus]. | There is a facility, coor_g.php, mainly used by Wikipedia, which takes an OS grid reference, converts it to latitude and longitude and links to a map sources page, thus: [http://toolserver.org/~rhaworth/os/coor_g.php?pagename=Beckingham_Palace¶ms=TL473132_region%3AGB_scale%3A25000 TL 473 132]. Streetmap.co.uk offers a facility to display the current location in a number of coordinate systems [http://streetmap.co.uk/idgc.srf?x=547350&y=213250 thus]. | ||
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| + | There are noticeable differences between coor_g's idea of gridref → lat/log conversion and streetmap's as can be seen by clicking on the links in the table below. In the worst case (top left of the table = north west) there is a difference of 39 metres in longitude. (The latitude figures show reasonable agreement throughout.) That example is all at sea - the worst case for actual GB land is {{smf|1000|900000|Soay, St Kilda}} where the difference is 24 metres. | ||
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| + | Who is right coor_g or streetmap? | ||
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Current revision as of 18:35, 25 February 2011
There is a facility, coor_g.php, mainly used by Wikipedia, which takes an OS grid reference, converts it to latitude and longitude and links to a map sources page, thus: TL 473 132. Streetmap.co.uk offers a facility to display the current location in a number of coordinate systems thus.
There are noticeable differences between coor_g's idea of gridref → lat/log conversion and streetmap's as can be seen by clicking on the links in the table below. In the worst case (top left of the table = north west) there is a difference of 39 metres in longitude. (The latitude figures show reasonable agreement throughout.) That example is all at sea - the worst case for actual GB land is Soay, St Kilda where the difference is 24 metres.
Who is right coor_g or streetmap?
| 0 | 100 km | 400 km | 700 km | ← eastings |
| 0,1300 | 100,1300 | 400,1300 | 700,1300 | 1300 km north |
| 0,800 | 100,800 | 400,800 | 700,800 | 800 km north |
| 0,400 | 100,400 | 400,400 | 700,400 | 400 km north |
| 0,0 | 100,0 | 400,0 | 700,0 | 0 north |
