U T M or LAT/LONG

Mal, I only use UTM (Univeral Transverse Mercator) for all the right reasons.
Can you post an e-mail address and I will send you comprehensive information on the two systems and where to find all the information about UTM. The great thing about UTM it is all meaningful and in metric.

Basically, UTM is for land lubbers, and Degree, Minutes and Seconds is for the water lovers.

Yeah,

UTM will give you a grid ref that can be read off 1:250,000maps etc and because of the scales and lines on the maps, I tend to think are more accurate. The marine bunch, of which I have been guilty, use the lat/lon measurements which will also give you a position, just using a different method. I do notice that many GPS refs given on land, by both guide books and maps are also given as lat/long measurements, which in a GPS will be equally as accurate as using UTM. Military folk I think also use UTM as do bushwalkers etc. Horses for courses matey, whatever you prefer. With my GPS (Magellan 315) I can have a primary and secondary co-ord system, and have UTM as primary and Lat/long as the secondary, so depending on the map I use, I can flick between the two, though keep an eye on the map datums!

Regards
Slunnie

Hi there

UTM stands for Universal Transverse Mercator - it's both the grid coordinate system and the projection used on all topographic maps. The Australian equivalent of UTM is AMG (Australian Map Grid) or the new MGA (Map Grid of Austraila). Like one of the replies said it's very logical once you get to use it as it's all metric so this makes distance calculations between points quite easy. Points are given in Eastings and Northings. One catch with UTM is that you must know what UTM zone you are in or your position can be out by hundreds of metres.

Latitude and Longitude is the original system developed centuries ago and is still the standard particularly in marine circles. These positions are given in degrees minutes and seconds - just like time, 60 seconds in a minute etc. The earth is divided up into 180 degrees east or west of Greenwich and 90 degrees north or south of the equator.

There are 3 issues to be a aware of when using your GPS with your map. These all affect the mathematical calculations used to convert the curved 3D earth into a flat 2D map:

1. Map Projection eg Universal Transverse Mercator (used for most world maps), Lambert Conformal Conic, Simple Conic etc. (NB A projection can not be set on your GPS)

2. Coordinate System - UTM or Lat/Long - this is a personal choice when it comes to waypoints and it's up to you what you use. The map you're using your GPS with will in reality determine which one you will need to use. UTM is only useful on a map up to 1:250,000 as beyond this it becomes very inaccurate as the square grid can no longer account for the curvature of the earth. That's where lat/long comes into it's own and that's why most regional maps use lat/long.

3. Map Datum eg WGS84, AGD66, GDA94 etc these datums are related to the Australian Survey height controls. There is a 200m shift to the north east between AGD66 and WGS84. WGS84 and GDA94 are basically identical with only a few centimtres between them.

I know that it a very mumbo jumbo summary but there is lots to it as you can see. The best thing to do is just go out for a few hours use your common sense and nut it out for yourself.

There are also some good cheap books on all this available from your local map shop.

Have a great day

Rob

As I understand it Brian the datum is very important if you wish to be accurate with your navigation. A lot of countries use a fixed known point upon which all mapping data is measured from. Can you imagine if Australia used the Greenwich meridian as a point to measure all their mapping points from? We are so far from it that a little error might creep in by the time the tape measure waas moved a few thousand times around the globe!!!!! Thus we have our own datum (don't ask me where it is--- Perhaps Sydney or Canberra. There are also several Aust datums. They generally start with WGS***

thanks for the info looks like in need to read more .U T M looks easier to use ie almost like a melway. safe driveing MAL/B.