archiv~1.txt: RE: SETI Grid Square Locators

RE: SETI Grid Square Locators

Adrian W Kingsley-Hughes ( (no email) )
Sat, 13 Mar 1999 18:49:36 -0000

As mapped by the Ordnance Survey, Great Britain is covered by 100 x 100 km
grid squares identified by two letters (91 in all - 7 across, 13 upwards).
The origin of this grid is about 110 km west and 20 km south of Land's End.
On the Ordnance Survey maps these squares are further divided by grid lines
representing 10 km spacing, numbered 0 to 9 from the southwest corner in an
easterly (left to right) and northerly (upwards) direction. Using this
system you can identify a 10 km square grid. On the more detailed maps
(Landranger) you can further divide up the grid into 1 km squares.

Using this method you get an Ordnance Survey grid reference. It takes the
following format:

SH551725 (my station's location)

The first two letters are the sheet identifier. The next three digits give
the eastings along the grid and the final three digits give the northings.

For those finding it difficult to remember that eastings come before
northings, then remember to go "along thew hall and up the stairs".

For more information visit the OS site:
http://www.ordsvy.gov.uk

For conversion details download the following .PDF file (113 kb)
http://www.ordsvy.gov.uk/about_us/pdf/gipaper1.pdf

What system is used in other countries? The OS system is a very good system
indeed. An advantage of it is that if you want to find the distance between
two points then you can use Pythagoras' theorem.

Pythagoras' theorem states that in a right angled triangle, the square of
the length of the hypotenuse equals the sum of the squares of the other two
sides. As eastings lines are perpendicular to northings, it can be used to
calculate the distance between the two points (ie the hypotenuse) by just
calculating the difference in eastings by subtracting the smaller figure
from the larger, and then calculating the difference in northings by
subtracting the smaller figure from the larger. Now square the two results
and add together, now the square root of this result is the length of the
hypotenuse. Using this method you can get a value in meters.

For a worked example see:
http://www.ordsvy.gov.uk/literatu/info/cr212.html

Hope this helps.

Cheers

Adrian

Adrian W Kingsley-Hughes - Technical Director
Mobile: +44 (0)966 497032
Mobile fax: +44 (0)7970 099283

Kingsley-Hughes Development Ltd
PO Box 2 - BANGOR - Gwynedd - United Kingdom
http://www.khd.co.uk

> -----Original Message-----
> From: owner-seti@lists.sni.net [mailto:owner-seti@lists.sni.net]On
> Behalf Of n6tx@setileague.org
> Sent: Saturday, March 13, 1999 5:24 PM
> To: Seti (E-mail); Argus (E-mail)
> Cc: rcf@setileague.org
> Subject: RE: SETI Grid Square Locators
>
>
> ----Original Message-----
> >From: "Adrian W Kingsley-Hughes" <awk-h@dolwar.demon.co.uk>
>
> >Here is a cool Grid Square locator for those of us in the
> UK who want to
> >work it out from the OS Grid Reference:
>
> Thanks, Adrian. Perhaps for the benefit of those of us not
> in the UK, you could explain a bit about the OS Grid system?
>
> >For those not in the UK, here is one to work it out from
> Lat and Long:
>
> There are two more of these linked from the SETI League
> website. From the Alphabetical Inde, look up "Grid Square."
>
>