Re: Lat/long and grid references

To: David McDonald <>
Subject: Re: Lat/long and grid references
From: (Chris Dahlberg)
Date: Mon, 19 Oct 1998 16:38:27 +1000 (EST)
Hello Everyone 
               I will have ago at this:

     Geographical Coordinates(Lat & Long) were in use before Rectangular
Coordinates(grid references) with regard to CHARTS and MAPS. 

     Centuries ago mariners found it relatively easy to establish Latitude
by measuring the angle the sun was above the horizon with a crosstaff as it
transited the observers meridian(north south line). As the
declination(celestial latitude) of the sun could be predicted by date a
simple calculation (in 2 dimensions) could produce a fairly accurate
Latitude. And centuries went by with out producing a reliable Longitude
because the accurate time pieces needed that did exist were unsuitable for
going to sea and radio waves that could send accurate time signals were in
the future. It was naval tradition that put Latitude first and for hundreds
of years there was only Latitude anyway.
     The landlubbers were starting to refine the maps, and without a perfect
horizon(the sea) that could be used as a datum to measure vertical angles
from and lots of landmarks instead, magnetic compasses were used to resect
the observer on the ground. Rectangular coordinates or graph coordinates use
measurements along an X axis and then measurements along a Y axis in exactly
that convention. This time the X measurements or eastings are so many metres
to the right or east of an origin outside and to the left of the map and the
northings are so many metres up or to the north of the same origin outside
and to the bottom of the map. Actually this origin is the false origin that
is placed there so that the eastings and northings always have a positive value.

    The Navy got there first and in fine naval tradition were not about to
change. At formal navy dinners I think they still toast the Queen whilst
seated, this is because the deckhead(ceiling) in ships was low and there is
nothing quite so ridiculous as not knowing if a staggering sailor was
concussed or drunk. If you see a staggering sailor you know it is probably
the latter and not the former.

see ya

>With the advent of the Birds Australia Alas, GPS receivers have become
>as important a piece of birding equipment as binoculars and field
>guides. Well, almost, anyway. Probably I am not the only person who
>finds it a pain to identify accurately my latitude and longitude from
>the AUSLIG 1:100,000 maps, the type I usually use, when I do not have my
>GPS receiver with me. Having used grid references on these maps (and the
>1:63,360s before them) for most of my life I find the switch to lat/long
>a bit of a pain. (Yes, I have and sometimes use the Excel spreadsheet
>provided by AUSLIG for for converting between grid refs and lat/long,
>but it is all a bit tedious.)
>One thing intrugues me. With grid references we conventionally cite the
>easting followed by the northing. There is no choice in the matter. But
>with latitude/longitude we conventionally do it the other way round: nn
>degrees/minutes/second South (latitude) followed by nn
>degrees/minutes/seconds East (longitude). The GPS receivers' readouts
>also deal with them this way.
>Does anyone know how we came to have these differing sequences?
>David McDonald
>David McDonald
>PO Box 1355, Woden ACT 2606, Australia
>Tel: +61 2 6231 8904 (h); +61 2 6249 5618 (w)
>Fax: +61 2 6249 0740

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