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Coordinate system


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Hi, I'm new to geocaching but have some experience of navigating from 10 years in the Army. I don't yet have a GPS but hope to soon get a Magellan SporTrack. I am used to working with a grid based coordinate system that topographic maps in Australia use. I am not sure if topographic maps in other countries use the same system. A typical grid ref I'm used to would be "876547", which of course is specific for each map, using the eastings and northings. What I want to know is, how can one easily convert grid bearings to lat and long and vice versa? It seems the coordinates downloaded from this site are lat long. I haven't yet used a GPS but have downloaded the manual and have installed and downloaded to EasyGPS.

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One issue with Australian charts/Maps at the moment is the mixture of datums as things are changed/updated from the old(er) AGD66 or AGD84 datums to GDA94 (WGS84).


Important to make sure of the datum of the coordinates before converting to/from lat/long.


As long as you know the full AMG coordinates (and Zone) in either AGD66/84 (Australian Geodetic Datum 1966 or 1984) or MGA94 (Map Grid of Australia 1994) then converting either way won't be a problem using most (not all) GPS receievers or conversion software like GDay or GDAit etc.


This conversion software is freely available was well as national distortion models but if the GPS receiever does it then probably better to do it that way.


Cheers, Kerry.


I never get lost icon_smile.gif everybody keeps telling me where to go icon_wink.gif

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Hi, thanks for answering. The map I am using states Geocentric Datum of Australia. I am thinking of getting a garmin eTrex Venture, it seems the best for the money, only 1 mb but satelite aquisition seems fast compared to Magellan (15 secs compared to 1 min). Do u know of this system converts lat long to GDA? It would seem a hassle to me if not, as I want to use the GPS as an addition to a map, not instead of a map.

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GDA for all intent and purposes is identical to WGS84. The Etrex converts things ok.


GDA94 is a datum so positions can be Lat/Long as well as UTM. UTM coordinates in GDA94 are commonly referred to as MGA (being Map Grid of Australia).


The Etrex will accept either Lat/Long or UTM in WGS84 (GDA94) and allow the user to configure the position format display as either Lat/Long or UTM.


Will also allow the input of AGD66/AGD84 (Lat/Long or UTM(AMG)) and allow conversion to GDA94 (WGS84) and vicversa.


Cheers, Kerry.


I never get lost icon_smile.gif everybody keeps telling me where to go icon_wink.gif

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