Re - GPS Datum

G'day John,

That is a rather vague statement which you quote mate.

for starters, what scale of map are these people quoting where they state that accuracy is increased by that amount - 1:25,000, 1:100,000, 1:250,000??

You can see where I'm going with that.

Don't always believe what you read in books - especially if they are written by people who make a living from such publications.

Believe textbooks.

Datum is very important for precise navigation, and to that end, the datum detail which your GPS should be set to for the paticular map you are using, will always be found in the marginial information of that map.

For instance, if you have a 1:100,000 map of Cooktown area you will note that its datum is Aus Geodetic 1966 - or AUS 66 as it is commonly known.

To navigate accurately in that area your GPS MUST be set on AUS66.

the same applies with the other main Aus datum ref GDA94.

GDA 94 is the equivalent of WGS84, and is fast becoming the benchmark as new maps are surveyed.

For instance, the 1:100,000 map of Ipswich and surrounding area is GDA94 [WGS84] and you must have your GPS set on WGS84 for accuracy.

The bottom line is, always note your Datum detting from the marginal info on your map, and set your GPS accordingly.

As you move around the country - check the datum of each new map as you bring it into use. It is quite common for adjoining maps to have different Datum references.

You can see the potential problems there if you are going from one small scale map to another and need precise accuracy. Ask an artilleryman :) :) :)

Never put your trust solely in what is written in "somebody's book" - however well sourced it may seem.

Learn your craft from a good text book - or some other reliable source.

regards

DennisN

Merry Christmas John,

Our Artillery friend is absolutely right. Set the GPS datum to that of the map and refer to a good text.

There is a text book that gives the basics called 'Exploring GPS', published by GPSCO and TAFE. It is usually available from technical book shops and a growing number of outdoor and 4wd shops (even ExplorOz). It's gives you good a background to GPS and how it works, without bogging you down with too much of the technical stuff, followed by a series of excersises to help familiarise you with the use of the GPS.

Enjoy your new GPS. You'll find it's a good addition on the dashboard.

PlutoGet out there & have Fun!!!