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British national grid

Started by english si, March 15, 2013, 11:30:14 AM

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english si

In a similar vein - no part of the UK proper (ignoring territories and crown dependencies) gets within 100km the 49th parallel. The official national grid references start in the SW corner 100km north of the 49th, and 400km west of the 2nd (west).

By almost pure fluke, the 'big' 1000km by 1000km squares that cover Britain are S, T, N and H - I used to think they stood for South, Thames and North (didn't know about H). Annoyingly H is a bit too far north to cover the Hebridies or Highlands. The truth, however is that it's just the middle (or the east of the middle - Ireland originally planned to be in?) of a big A-E, F-K (no I), L-P, Q-U, V-Z grid.

There's also a tiny part of the coast in the 100m square OV 000 000 - but they don't like to talk about that. Nor the Channel Islands in big square X. Quite why they don't map the Channel Islands using the national grid, I don't know. The Isle of Man gets OS maps, and there's surely OS data on the Channel Islands, but they neither publish the maps, nor do those based on the data use the National Grid (my 60s one uses some world-wide 1km grid pattern).

I guess, like mentioning big square O, mentioning XD and XE (XE 000 000 is 49N 2W, and a bit south of Jersey) is going to reveal the secret grid stretching from Iceland to Italy...


djsinco

Quote from: english si on March 15, 2013, 11:30:14 AM
In a similar vein - no part of the UK proper (ignoring territories and crown dependencies) gets within 100km the 49th parallel. The official national grid references start in the SW corner 100km north of the 49th, and 400km west of the 2nd (west).

By almost pure fluke, the 'big' 1000km by 1000km squares that cover Britain are S, T, N and H - I used to think they stood for South, Thames and North (didn't know about H). Annoyingly H is a bit too far north to cover the Hebridies or Highlands. The truth, however is that it's just the middle (or the east of the middle - Ireland originally planned to be in?) of a big A-E, F-K (no I), L-P, Q-U, V-Z grid.

There's also a tiny part of the coast in the 100m square OV 000 000 - but they don't like to talk about that. Nor the Channel Islands in big square X. Quite why they don't map the Channel Islands using the national grid, I don't know. The Isle of Man gets OS maps, and there's surely OS data on the Channel Islands, but they neither publish the maps, nor do those based on the data use the National Grid (my 60s one uses some world-wide 1km grid pattern).

I guess, like mentioning big square O, mentioning XD and XE (XE 000 000 is 49N 2W, and a bit south of Jersey) is going to reveal the secret grid stretching from Iceland to Italy...
What?
3 million miles and counting

english si

Quote from: djsinco on March 15, 2013, 11:52:55 AMWhat?
Let me clarify that for you.

In a completely different, but related, vein to Canada going south of the 49th - no part of the UK proper (ignoring territories and crown dependencies) gets within 100km the 49th parallel. The official national grid references start in the SW corner 100km north of the 49th, and 400km west of the 2nd (west).

By almost pure fluke, the 'big' 1000km by 1000km squares that cover Britain are S, T, N and H - I used to think they stood for South, Thames and North (didn't know about H). Annoyingly H is a bit too far north to cover the Hebridies or Highlands. The truth, however is that it's just the middle (or the east of the middle - Ireland originally planned to be in?) of a big A-E, F-K (no I), L-P, Q-U, V-Z grid.

There's also a tiny part of the coast in the 100m square OV 000 000 - but they don't like to talk about that. Nor the Channel Islands in big square X. Quite why they don't map the Channel Islands using the national grid, I don't know. The Isle of Man gets OS maps, and there's surely OS data on the Channel Islands, but they neither publish the maps, nor do those based on the data use the National Grid (my 60s one uses some world-wide 1km grid pattern).

I guess, like mentioning big square O, mentioning XD and XE (XE 000 000 is 49N 2W, and a bit south of Jersey) is going to reveal the secret grid stretching from Iceland to Italy...

agentsteel53

it helps to note this image

live from sunny San Diego.

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jake@aaroads.com

kkt

Quote from: english si on March 15, 2013, 12:45:33 PM
Quote from: djsinco on March 15, 2013, 11:52:55 AMWhat?
Let me clarify that for you.

In a completely different, but related, vein to Canada going south of the 49th - no part of the UK proper (ignoring territories and crown dependencies) gets within 100km the 49th parallel. The official national grid references start in the SW corner 100km north of the 49th, and 400km west of the 2nd (west).

By almost pure fluke, the 'big' 1000km by 1000km squares that cover Britain are S, T, N and H - I used to think they stood for South, Thames and North (didn't know about H). Annoyingly H is a bit too far north to cover the Hebridies or Highlands. The truth, however is that it's just the middle (or the east of the middle - Ireland originally planned to be in?) of a big A-E, F-K (no I), L-P, Q-U, V-Z grid.

There's also a tiny part of the coast in the 100m square OV 000 000 - but they don't like to talk about that. Nor the Channel Islands in big square X. Quite why they don't map the Channel Islands using the national grid, I don't know. The Isle of Man gets OS maps, and there's surely OS data on the Channel Islands, but they neither publish the maps, nor do those based on the data use the National Grid (my 60s one uses some world-wide 1km grid pattern).

I guess, like mentioning big square O, mentioning XD and XE (XE 000 000 is 49N 2W, and a bit south of Jersey) is going to reveal the secret grid stretching from Iceland to Italy...

What an interesting way to number the grid.  Was it created to confuse the French Germans?

djsinco

Do those grid lines correspond to latitude/longitude lines?
3 million miles and counting

english si

Nope - they correspond to a far more useful equal area 100km x 100km squares (subdivided into 1km x 1km squares). See the blue lines here for the smaller squares (the thicker ones are 10km lines). There are blue crosses every (IIRC) 10 minutes marking long/lat.

There are numbers on the maps, which give you eastings and northings (along the corridor and up the stairs). And you typically go with 6-figure 100m accuracy, doing the latter by eye (though you can get devices to do the tenths, typically also being able to do 100ths for 8-figure grid references). The Victoria memorial, in the roundabout in front of Buckingham Palace is at TQ 290 797, though you wouldn't typically need the TQ. Works better on the paper maps.

Makes organising competitive hikes/orienteering for Scouts, etc easier - put flags/checkpoints at certain GRs, getting them to navigate and was considered important enough to teach us it at school.

djsinco

So, do they also serve as postal codes?
3 million miles and counting

english si

No, postal codes are a different alphanumeric system, based on internal workings of the Post Office (letters for sorting office, number for more local sorting office, space, number for round number, two letters for a couple of houses).

J N Winkler

#9
Wikipedia has a fairly detailed account of UK postcodes.  Postcode districts are often used as shorthand for the large institutions located in them in much the same way we use telephone area codes--for example, "SW1" is often used as a generic reference to the British government, much as "202" refers to Washington.  (In fact SW1 has been subdivided, as is occasionally done with postal districts by adding a letter prefix, and most government departments now have their central offices in SW1A.)

Google Maps has actually done more to enable search for British postcodes than it has for ZIP codes.  If you search for a geographical ZIP code (e.g. 67212), it will be highlighted in red.  If you search for a nine-digit ZIP code within that five-digit code (e.g. 67212-1842), it will not take you to the house group represented by that ZIP code; instead, the whole 67212 area will be highlighted.  On the other hand, if you search for a British postal district (e.g. OX1), the entire postal district will be highlighted in red.  If you search for a specific postcode within that district (e.g. OX1 4AW), it will zoom to the building group that corresponds to that postcode, although it won't highlight the buildings that are actually in that group.

British postcodes are more economical than nine-digit ZIP codes in writing because they have the same level of specificity but with fewer alphanumeric characters.  In the examples given above, "672" is basically a posttown (Wichita) and the five-digit ZIP code is analogous to a postal district.  (67212 is conceptually "Wichita 12" but I am not sure there was actually a 12th postal district in Wichita before the old city-district system was abandoned in favor of ZIP codes in 1963.  67212 is primarily residential and light commercial and most of its building development did not occur until well after the Korean War.)  That is an uniform five digits to do what British postcodes do in less than four characters (usually three, but can be as low as two in an urban district in a large posttown).  The four-digit extension, introduced in the 1980's to enable electronic sorting, takes four digits to do what a British postcode does with three alphanumeric characters.  The only advantages nine-digit ZIP codes have, as far as I can see, are uniform width (always nine characters) and a hyphen that visually unites all the postal coding information in a single block.

British postcodes have the additional advantage that the posttowns are usually intuitively easy to decode.  Usually all you can get from the first one or two digits of a ZIP code is a broad idea of which part of the country the address is in (most people, for example, don't have the granularity of knowledge to recognize that 66 or 67 means Kansas while 68 means Nebraska, let alone to recognize 672 as Wichita, 665 as Manhattan, 666 as Topeka, etc.).
"It is necessary to spend a hundred lire now to save a thousand lire later."--Piero Puricelli, explaining the need for a first-class road system to Benito Mussolini

Duke87

Heh. When I first saw the thread title I thought it would be about this.
If you always take the same road, you will never see anything new.

oscar

Quote from: J N Winkler on March 16, 2013, 11:36:58 PM
Google Maps has actually done more to enable search for British postcodes than it has for ZIP codes.  If you search for a geographical ZIP code (e.g. 67212), it will be highlighted in red.  If you search for a nine-digit ZIP code within that five-digit code (e.g. 67212-1842), it will not take you to the house group represented by that ZIP code; instead, the whole 67212 area will be highlighted.  On the other hand, if you search for a British postal district (e.g. OX1), the entire postal district will be highlighted in red.  If you search for a specific postcode within that district (e.g. OX1 4AW), it will zoom to the building group that corresponds to that postcode, although it won't highlight the buildings that are actually in that group.

There seems to be a lot of variability in how nine-digit ZIP codes in the U.S. are broken out within five-digit ZIP code areas.  Some places it's broken down by neighborhood or carrier route.  Others, each house has its own nine-digit ZIP code (I know some of my relatives have their own unique 9-digit ZIPs).  And P.O. boxes usually get their own individual 9-digit ZIP codes.  Google Maps' approach, to ignore the last four digits of nine-digit U.S. ZIP codes, seems sensible to me.
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kphoger

Quote from: oscar on March 17, 2013, 11:34:59 PM
Quote from: J N Winkler on March 16, 2013, 11:36:58 PM
Google Maps has actually done more to enable search for British postcodes than it has for ZIP codes.  If you search for a geographical ZIP code (e.g. 67212), it will be highlighted in red.  If you search for a nine-digit ZIP code within that five-digit code (e.g. 67212-1842), it will not take you to the house group represented by that ZIP code; instead, the whole 67212 area will be highlighted.  On the other hand, if you search for a British postal district (e.g. OX1), the entire postal district will be highlighted in red.  If you search for a specific postcode within that district (e.g. OX1 4AW), it will zoom to the building group that corresponds to that postcode, although it won't highlight the buildings that are actually in that group.

There seems to be a lot of variability in how nine-digit ZIP codes in the U.S. are broken out within five-digit ZIP code areas.  Some places it's broken down by neighborhood or carrier route.  Others, each house has its own nine-digit ZIP code (I know some of my relatives have their own unique 9-digit ZIPs).  And P.O. boxes usually get their own individual 9-digit ZIP codes.  Google Maps' approach, to ignore the last four digits of nine-digit U.S. ZIP codes, seems sensible to me.

How well does Google Maps do for Canada's postal codes, which seem similar to the UK's?

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Male pronouns, please.

Quote from: PKDIf you can control the meaning of words, you can control the people who must use them.

J N Winkler

Quote from: kphoger on March 18, 2013, 01:16:00 PMHow well does Google Maps do for Canada's postal codes, which seem similar to the UK's?

Canadian postal codes are a bit of a mindfuck and emblematic of how Canada is a child of difficult parents (noisy and over-affectionate one to the south, distant and cool one on the other side of the Atlantic).  Their resemblance to British postcodes is entirely superficial, beginning and ending with the white space in the middle.  There is no explicit posttown-postal district structure and the alternation between alphabetic characters and digits is fixed.  Underneath the skin they are essentially ZIP codes.

Trying L0G 1J0 (Kettleby, Ontario) in Google Maps, we see the shading responds to the amount of the postcode that is entered:

L0G

L0G 1J0
"It is necessary to spend a hundred lire now to save a thousand lire later."--Piero Puricelli, explaining the need for a first-class road system to Benito Mussolini

agentsteel53

Quote from: J N Winkler on March 16, 2013, 11:36:58 PM666 as Topeka

that's about the only one I've got memorized.  perhaps the one positive contribution Fred Phelps has made to our society: making his zip code more mnemonically convenient.
live from sunny San Diego.

http://shields.aaroads.com

jake@aaroads.com

kkt

Quote from: J N Winkler on March 18, 2013, 05:05:52 PM
Canadian postal codes are a bit of a mindfuck

But they have the coolest postal code for Santa Claus!  H0H 0H0



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