Portable GPS - what do I need to know?

I use TomTom Nav5 on a Palm T|X with bluetooth. Works great for road navigation. Never tried it 'off road.' Have a look at their website. They have many different products, so something may work for you.

Like Rico, I have been thinking about buying a hand-held GPS unit. The cheapest I've seen is Garmin e-trex at under £100.

At this price you seem to get your "position" and presumably a "bearing and distance to your next pre-programmed way-point".

Does it provide GPS derived altitude?
How accurate is the information
Will it work world-wide straight out of the box

At £350 I've seen the Garmin E-Trex Vista which seems to have a moving map and a barometric altimeter. Now a barametric altimeter is totally useless unless you can set it to compensate for atmospheric pressure variations, so again, I presume this is provided by the GPS satellite data? Also, I presume you need to buy the moving map data separately and load it up via a modern computer (mine is a 10 year old Dell running on Windows 95) How expensive is this and is it really useful?

Lots of questions........

Cheers

Don

I use tomotom symbian on a Nokia 6680 via a blutooth to a dinky little gps thingy purchased from ebay.

If you need to know any more let me know.

andy c!

Tomtom 5 is as good on foot as in the car. No altitude reading that I know of - I'd check the website. I have it on a PDA with a BlueTooth GPS receiver. Battery life of the PDA is a critical factor. No problem in the car obviously.

FWIW

Cheers

quote:

Like Rico, I have been thinking about buying a hand-held GPS unit. The cheapest I've seen is Garmin e-trex at under £100.

At this price you seem to get your "position" and presumably a "bearing and distance to your next pre-programmed way-point".

Does it provide GPS derived altitude?
How accurate is the information
Will it work world-wide straight out of the box

I do quite a bit of treking in mountains - Scotland and Western Canada
Being able to confirm your Lat/Long by GPS would be very useful, but confirming your altitude can be significantly more useful eg when trying to confirm your position on a rising ridge.

The shop assistants (eg Cotswold) can't answer the three questions above and none seem inclined to get a GPS up and running to find out!

Any practical experiences gratefully received.

Cheers

Don

GPS receivers use WGS84 (World Geodetic System 1984) datum, last updated in 2004. They work worldwide out of the box.

Since the US commenced phasing out their intentional degradation of the system in 2000 claimed horizontal accuracy has improved from around 44 metres to 3 metres (typically 1 metre at the equator or about 1.5 metres in the UK for example) assuming a good spread of four or more satellites.

Similar claims are made for vertical accuracy, which is a feature I don't use in my work. I did get a reading of 150 metres below sea level once from an older machine though!

I have used both hand held and fixed GPS receivers (augmented by radar) at sea for precise fixing of marine park boundaries and fishing closures & have a lot of confidence in the system. The only real problem you might have is if you are plotting your position onto old maps which use OS (Ordnance Survey) datum, assuming you're in the UK, here in Australia the obsolete datum is ADG66). Doing this will put your position out by at least 200 metres. Be very careful how you use paper maps with GPS.

All maps produced in the past ten or so years use new GDA94 datum, which is compatible with WGS84, so the problem is removed. The datum should be clearly marked on the map.

Newer hand helds take SD memory cards and have about 15 hrs battery life from two AA alkalines, pretty good stuff.

I would check out some of the posts on www.singletrackworld.co.uk regarding this topic.

Eric

thanks all for the feedback.

we were putting together a leaving gift for a colleague, and figured we could just about manage one of the garmin eTrex models, for portability, mapping potential, and the crossover uses of camping truck touring, and adventure motorcycling.

another colleague (keen on hunting) explained the use of the digital compass and electronic harpoon, available on some of the models. If there's one thing I have learned, there's a vast range across many manufacturers, with many different options and features.

found the following basics:
* 12 channels or better desirable
* higher res better (in this case, 160x288 is what we could afford)
* mapping capability - more memory better, some take SD cards
*consider batty life
* consider durability in your intended operating environment
* PC connectivity
* manufacturer support - free updates? any updates?

we scored a Legend, and are very excited about presenting the gift.

cheers!

quote:

Originally posted by Rico:

we scored a Legend, and are very excited about presenting the gift.

cheers!

Awesome! That should be extremely useful traveling between The Warehouse and any number of coffee haunts on Saturday mornings....



Jay

PS. TomTom. To the Tesco please...

heh heh - he's going to be about as far and remote from the warehouse, courtenay place coffee haunts, or tescos as is imaginable. "computer - set the controls for the black stump".