Nice watch with almost useless sensors
Good watches but sensors are really weak. I can trust only results that barometer or watches are showing. Sometimes compas is showing correct results, but it really sensitive and may change direction because of quite small pice of iron. Thermometer has big error so it does not really make any sence to show degrees with decimals. Altimeter is highly dependent on presure, so it can be used only withing sort ranges, so I don't really understand when altimeter can be really used.
So far, this watches are nice device for people who are not really interesting in good results of such sensors (as it was mentioned in maunal). However, if you really need device with good and accurate sensors I would recomend to look for bit more expencive models. If you are traveling a lot in wild nature or if you are interesting in parachuting sport, then you should not take this device.

Big, but not quite as rugged as it might appear
(Based on owning this watch for more than five years)

The first thing anyone notices about this watch is that it is big...huge in fact.

For me this isn't a major problem and in fact is exactly why my girlfriend (now wife) bought it for me - she knew I like gadgets and she knew most watches look like toys in comparison to my 6 ft 4in, 17-stone frame. It's one of the reasons the watch works for me.

So while it matches my size, I imagine smaller people would find their wrists and hands dwarfed and overpowered by this chunky watch. The face is around two inches across and the watch itself is more than half an inch deep.

While this is fine for outdoor activity, I struggle to get a shirt cuff over it - so be prepared to have your watch on show most of the time.

Keeping that mass on your wrist is a heavy-duty plastic strap, which sadly looks a little cheap considering the price of the watch. It's also strange that Casio decided to use a plastic strap in a watch primarily designed for active wearers - it encourages sweat build up and some big cavities on the underside of the watch and strap seem custom designed to catch that horrible, white, dirty crud that is left behind after a hot days climbing/skiing/walking.

My previous watch - another hefty beast of a G-shock - at least had a fabric strap and the option to change straps, which this watch lacks.

Billed as a "triple sensor Protrek" in the UK, the watch features altitude, temperature, direction and pressure readings - as well as telling the time and date. There are the usual alarm functions, although it's not the loudest alarm in the world and I've never trusted it to wake me up.

The watch can also store sensor readings over a period and represent changing pressure/altitude/temperature on a small LCD graph - which is quite nice for the weather nerds amongst us.

The compass again appears to be largely accurate, although local electrical or magnetic fields can deflect it.

And one annoyance is the temperature gauge is only useful if the watch is left off your wrist for ten or twenty minutes, so your body warmth doesn't affect it.

Again, without being sure exactly how the watch calculates its readings, I'm not convinced it can't be fooled into thinking altitude has changed because pressure or temperature has gone up or down, and vice versa.

I've found it pays to recalibrate the watch at every opportunity to make sure the sensors remain accurate. Thankfully this isn't a hugely onerous task once you've mastered the technique from the manual and just relies on you cross checking the current temp/pressure/altitude on another instrument and feeding the results into the watch.

For example, if I find myself down on the beach, I'll take the chance to set the altitude to sea level.

All the information is presented in large, clear figures - thanks to that big watch face. The compass relies on clever multi-layered LCD technology which allows it to be displayed on top of the usual watch display.

Build wise, as you'd expect from the creators of G-Shock, the watch appears fairly indestructible - however shortly after purchase mine let water in when I accidently left it on in the shower, which doesn't inspire confidence in claims of being water resistant to 10-bar. Eventually Casio agree to repair free-of-charge, but only after three months of making a pain of myself...which doesn't inspire my confidence in its customer service.

Further disappointment was with the less sturdy plastic styling round some of the sensors. I'd managed to snap off a corner within a few weeks - and that was doing nothing more dangerous than the morning commute.

Failings aside, it's still a fine watch, appeals to my gadget loving side and never fails to spark conversation.

Robust
Bought this model over 5 years ago. Turned out to be a very good robust watch! Although it does make you look like an action man! Usability of some of the functions is debatable (altimeter, barometer). I've a friend who is an air force navigator and immediately pointed out the inaccuracies of these functions even when supposedly corrected for environmental conditions , HOWEVER I can say, I used this watch in compass mode to trek across the Sahara desert and it never let me down! Even in the middle of a massive sand storm when I opted to keep moving by use of the compass. Got me to within a few metres of my objective with 5 mtrs visability for the entire day!

Did have a problems once the batteries ran out (admittedly after 5+ years) as once new batteries were fitted it never worked quite like it did previosuly!

not bat, but a bit disappointing
basically a good product, but some drawbacks - maybe overpriced for what it is. for example, for the compass to work well the watch has to be flat.. the warning is if the watch is slightly at an angle, then the readings can vary drammatically. not a major deal but it means you have to stop if you want to confirm your direction and one of the reasons i wanted a compass strapped to my wrist is so i could check direction without stopping

secondly, a minor annoyance, is that I cant find a way to switch off that beep it makes everytime you press a button. pet hate of mine is things that beep at me.

finally, it would have been nice if they could have made it a bit slicker, at almost 1.7 cm thick you definitely know it's on your wrist.

on the plus side, the features do work well and they've been very good at documenting the limitations. the buttons are big and easy to find when you're moving and it certainly feels very robust.

Great watch but not ultimately accurate
I've had this watch for many years and has given me a lot of joy. It is useful in many situations if you are an outdoors type.

One gripe I do have about the watch is it's sensor for temperature and also altitude. You need to primarily set the altimeter to a location you know. Sometimes it is right, other times wrong but you do need to check it is accurate on the day you set out.

If you are out and about in the middle of nowhere, you may need a map to reset the altimeter again.

The thermometer also is off by some centigrade since it takes into account your body heat. You need to take the watch off for a while to get a more accurate reading or go by an estimation by knocking off 7 or 8 degrees from the reading on your hand.

Otherwise, you can tell changes in atmospheric pressure and therefore work out whether there is an oncoming change in weather. It has other available odds and ends you would expect from a digital watch and the compass is absolutely fantastic.

It's just wise to know of a few things before you invest the money for this watch.