Hi there Keri Boi, I use a "Garmin Plus II" in my 4x4, whilst hunting, and in the boat. I have an additional antenna and 12v connector for power. The unit is portable with its own batteries and antenna and it gives me good data when I want it.

Golf hole is a bit close as there is usually about 2m as said in discrepancy. In 2000 the Americans (Bill Clinton) removed the deliberate error readings and we all got instant improvement. However they kept the right to re-introduce those errors in the event of war! Thus at present we have at times a widening of the specific target for the GPS to track for, its only up to 15m however.

I used mine just yesterday to note a uncharted route in the Coromandels for a hunting trip so we could come out at the same spot yet from another approach angle, and the boys were sure pleased to come out by the 4x4 with the dogs and pig.

There's bigger and better GPS out there but the bucks sure increase with ability. The present day range has a lot of maps, both marine and topographical, and is smaller thus more able to be hidden in clothing till needed.

Ross

Hi Keri Boi,

A mate a Meridian HH. Likes it heaps. You can get road maps for it.

Why the golf course question??

1. Do you plan to put radar guidance in your golf ball to win the hole in one competition ???    Great idea if you are.

2. A lot of Golf courses move the location of the holes around the green.

As above the accuracy is only 2 metres, and can depend on how many satellites you are plugged into.

The accuracy of GPS fixes is a very complex subject and is given by the formula 'Accuracy = UERE X HDOP' where UERE is the User Equivalent Range Error and HDOP is the Horizontal Dilution Of Position.

UERE is a summation of various things like ionospheric delay, atmospheric delay, user clock error, stellite postion error, something called space pertubations (wobbly satellite orbits) and a few other things and all add up to 19.1m for 95% of the time with SA (Selective availability) turned off (that's Clinton's little prezzie to us all on 01/05/00) and about 62.5m with SA on. HDOP is to do with the geometry of the satellites the receiver is using to get a fix. Ideally the boat (or person) is in the middle of a triangle with one satellite directly overhead and three others on the horizon separated by 120 degree angles . This gives a HDOP of 1. Anything other than this gives a HDOP of > 1 and thus accuracy goes down. Most GPS receivers fail to process a fix if the HDOP is too high (above 2.5 or so I think). All the above is relevant if you are just using the satellites and not using DGPS. DGPS receivers which hook into the better GPS sets are fiercely expensive and are not relevant to  Handheld discussions.

The way I understand it, getting 2m accuracy out of an off the shelf GPS is not physically possible. The yellow Trimble things you see surveyors walking round the streets with in backpacks are accurate down to centimetres I think but don't really fit into the 'off the shelf' recreational category and have to be using some sort of land station (access to which is probably leased from Trimble at $X per month where X is a very large number) to cut out some of the inaccuracies that are inherent in all GPS fixes.

PS I'm sure C2C could usefully contribute here

Keri Boi,

Most, if not all Handheld GPS units now offer WAAS which is Wide Area Augmentation System The only problem is, that this service is not based off of Satellite Feedback, it is based off of ground units much like Cellular Phone towers. This service while it sounds great and works great is currently only available in the United States Market. NZ does not have it so your GPS unit will not initialize from it.

New Zealand has a decent GPS Satellite coverage. I am thinking between 3 and 6 Satellites in constallation if memory serves me correctly. The American Government does own the Satellites and they have the International Legal Right to scramble the signals globally "which they do" every time they make a stategic military strike. So what?

All you'll need is in a Garmin Etrex GPS. If you want more bells an whistles you just have to pay more. My Garmin GPS tells you it's margin of error. Most of the time it is around 2-3M. When I have marked a waypoint and gone back, it has been between 3 and 4m off. As the Americans say "Close Enough For Government Work."

My only complaint is that all Handheld GPS units suck down the batteries. Might as well have a unit that only uses 2 batteries instead of the usual four for the same time duration of power.

The only other GPS that was attractive to me was the Silva which had a dead nuts Compass on it that was not Signal Dependant. The catch was that 2 of the three I tested at different stores were defective out of the box. Meaning they would not interface with the statellites and Initialize.

Cheers

HF

what do you reckon... is it worth trying to catch a guided missile before it hits its target and pinching the sensitive gps guiding device out of it so we can have better gps marks??????? 

I like the Tomahawk Cruize Missile.

Any chance you could send that thing to Osama Bin Laden?

Im unfamiliar with gps brands.  anything that is portable and proced reasonably.