Map Data

Dave - interesting - they could be in feet or yards...if, as you mention, you know the actual location of some compare the coords that you have with current MGA coords...if the numbers are only about 200metres different then is justs AMG (66 and 84 are only ~3 metres different). If they are wildly different then it suggests yards....but without an example difficult to accertain from here. OziExplorer is good for changing data between datums ...but dont think yards is standard - my have to muck around with a user datum and projection. Can you provide an example coord and map sheet - this will be sufficient for me to determine issue.

Cheers
Greg

Hi David,
I'm no gun at mapping but have had some experience, even if itis AGD66 the point would still be relevent if the datum is incorrect it will just be out. is it poosible the point is out by about 200mtr? The only other way I might be able to figure it out would be to see the co ordinates. How many digits in each eastings and northings?
Regards Graham

Hi Dave,
you say that you have some points that you know in both systems while some of them you don't. In excel work out the difference in Northings and Eastings between the common points and then apply the difference to your funny coordinates.

ie old northing = 1000mN old Easting 5000mE
new northing 1000mN and new easting 7000mE
the adjustment from old to new will be +9000mN to all the old northings and +2000mE to the old easting.
give that a shot.

OK

Here are a couple

Map SE5514 1:250000
References given is 483364
and 487374

Both are meant to be on Mt Louisa

Some others

SE5514
References 485593 and 486394
Both are meant to be on the Many Peaks Range

I can't figure it out

Something wrong with my access to the forum, so can't post as a follow-up

Andrew

That is the conclusion I came to.
The co-ordinates came from a Thesis by an archeology PhD student from the 1970's, they just appear as six figure numbers with a map name like SE5510 in a table of data about specific locations.

Dave O

Andrew might be right a milatary system I have old Geo maps with co-ords in yards
try
Bob

Dave,

The coordinates might be using the Clarke 1858 spheroid as explained in www.ga.gov.au/geodesy/datums/ang.jsp

If the coordinates were taken from a map at the time (more than likely) then unless you have access to the map in question, the numbers may mean nothing.

You may not be able to convert easily......

Andrew

Hello - I think I have figured it out - the numbers given are yards using the universal Grid system (sometimes referred to the military grid system) or a version thereof.

And as far as I can figure there is also a mistake with your transcription (or someone’s) of the coords – you are reading some of the 5’s as 3’s (and hence the addition confusion created). If 3's are use the coords plot way out. Are the coords you have handwritten?

Ok in the examples you have given
Mt Louisa area
SE5514
References given is 483364 and 487374

These should be 483564 and 487574 (ie some 5’s have been misread as 3’s)

483564 represents 483000 yards East and 2564000 yards North
487574 represents 487000 yards East and 2574000 yards North

These don’t actually plot on Mt Louisa but along a river just south of it?? Mt Loiusa is actually at about 483583…so maybe I have got this all wrong….

Many Peaks Range
SE5514
References 485593 and 486394
The first one 485593 is right but the second should be 486594

485593 represents 485000 yards East and 2593000 yards North
486594 represents 486000 yards East and 2594000 yards North

These plot on the Many Peaks Range…so these look OK

I have taken these coords from the 250k Geology Map of the area using OziExplorer (I have all of Australia at 250K calibrated). This is the easiest way to convert the coords to something useable..unless you actually have a paper copy of the map which would also be handy. I do not know of a calculation that does the conversion. Also not all the Geology maps are “out of date” with yards shown and therefore useful for this purpose..but you may be lucky.

Anyway hope I have headed you down the right path.

Cheers
Greg