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theoldlegend
22-12-2007, 04:25 PM
Hello everybody,

I'm not too sure if this is the correct section to post this, but here goes anyway.

In my day, the stuff was in Imperial measurements, as in degrees, minutes and seconds. It was no problem for me to read maps and find coordinates. Military maps were a breeze. When I was in primary school, we even used to set up a sundial, which was a hoot, as you had to get things worked out to do it properly.

We recently visited some relatives near Warwick and I was given the coordinates of where they live. One of the coordinates reads " E152.11.383 min.

Now I guess we've moved into the metric age, where one degree which used to be a nautical mile equals 1.1515 statute miles which equals 1.8 something kilometres. The frustrating thing for me is that I can't seem to find anything on Google that can steer me in the right direction. Maybe I'm too old, or maybe I'm just too stupid to work it out for myself.

To get back to my question, is the reading I've given above, calculated to three decimal places of a minute, is in fractions of a kilometre? Does for example, 11.383 minutes mean 11.383 kilometres and what fraction of one degree is that.? How many minutes has to happen before you move up to say 153 degrees?

What's happened to the minutes and seconds where one used to be 1/60th of the other?? Have they disappeared?

Any advice would be appreciated. Please bear with me. I'm old. I'm tired.

Many thanks,

TOL

tunaticer
22-12-2007, 05:06 PM
G'day TOL,

The way I read the coords you have been given has got an extra decimal place instead of a space. You will probably find they are compiled on a spreadsheet and the decimal places instead of spaces will let them sort their coords out in either latitude or longitude.
Try Entering the coordinates as E152 11.383 etc and it should be right. Decimal degrees are like 152.238457 . Your coords supplied are decimal minutes as DD MM.MMM.

With your old way of recording coords as DD MM SSS you can easily convert those marks to decimal minutes by dividing the SSS part by 60. For example is you have a reading of 27°19'4.24"S divide the ".24" by 60 and you will obtain a result of 27 19.071 S.

As for a numerical distance on sea or land a degree of angle will vary in distance depending of latitude / longitude. The closer to the equator the greater the distance for east west distance and the closer to the poles the greater the distance for north / south distance.

For your local area calculations can be made to give a fairly precise distance over a degree so you can work out within a few metres true length over a hundred mile area.

Do you know what datum these marks were recorded in? There can quite a range of error between some datums.

Jack.