The PRW-2500 is, as far as I'm aware, Casio's most feature-packed watch, incorporating an altimeter, barometer and compass (ABC) as well as a thermometer, moon phase chart and tide graph on top of the more usual world time display, stopwatch and countdown timer. Like many other current Casio models, the watch is powered by a solar cell placed around the outer edge of the screen and has a basic `low, medium, high' power display indicator at the bottom. It also has a power saving mode, which turns the display off when the watch is in subdued light for an extended period of time, so helping to save battery power.
The watch's main screen is called the `home' screen and this displays the time and date (obviously) and the barometric trend for the past 10 hours. Each of the other functions has its own screen, accessed either through one of the direct ABC access buttons on the right-hand side of the watch or (in the case of the other functions) via the watch's menu system. The barometric trend graph for some reason is visible on most of the screens but missing from a couple, namely the altimeter records and countdown screens. Similarly, the moon phase information is displayed in the top-right corner of the watch's display but only on a couple of the screens.
I will say this now and get it out of the way - the manual the PRW-2500 comes with rivals War and Peace in scale. It notes every facet of each of the watch's various functions in detail, providing illustrations where necessary, and giving the user every piece of information he or she will need to work their new toy. Said information is, however, dotted around in what I consider to be a less-than-helpful manner, with no `quick setup' guide to get you started. You may have to read through the whole thing, learning the bits you need and disregarding the bits you don't, before you can properly get to grips with what the watch can do. Or you can (as I did) leave it in its factory settings and just play about as and when you need particular functions.
Although I haven't tested it against a `proper' compass, the one in my PRW-2500 seems to work fine, so if you experience problems with yours then it may be faulty, or there may be interference from an external magnetic source. One thing to note here - the compass only takes measurements for 20 seconds before switching off, so if you intend using it constantly then you'll have to keep selecting it.
I have had altimeters in a few Casio watches and I have never considered them to be particularly accurate, as they use pressure to calculate height, and the one in the PRW-2500 is no exception. The height it displays when I'm at home can vary by as much as 30 metres from day to day and although it may be more accurate when used out in the wild, I certainly wouldn't rely on it in a survival situation.
The barometer seems accurate enough, as does the trend graph and thermometer, although in the case of the thermometer the heat from your body will affect it greatly so I recommend that you take it off your wrist for a few minutes before you use it. The thermometer is only available on the barometer screen, but as the time is almost always visible, no matter what screen you're using, this is hardly a problem if you want to keep track of the temperature while keeping an eye on the time.
As well as having its own screen, the current day's tide graph data can also be viewed on the home screen by the press of the `adjust' button at the bottom. You first need to set the graph from the tide information in your local paper or online before you use it, but after that it appears to give a pretty accurate indication of the tides for both the current day or any other date that you select. I have found the tide graph to be reasonably accurate, but it does depend on the user having set their home city and date/time correctly. I'm using London as my home city as it's the nearest choice to me, but as it's around 180 miles from where I live, this does seem to have an effect on the accuracy and I have to adjust the graph manually around once a week to keep it within tolerances. As the Casio blurb says, "This watch is not an instrument for calculating low tide and high tide times. The tide graph of this watch is intended to provide a reasonable approximation of tidal movements only".
The PRW-2500 uses a lovely duplex display, overlaying a blue LCD on top of the main one, and Casio have used this upper LCD to display the compass and tide graph information. The information `floats' just above the main LCD, giving the display a very slight 3D effect and allowing more information to be shown at any one time than a single LCD could. The display has a green backlight that turns on when you press the `light' button, and also when you angle the watch towards you, although that method can be turned off in the menus if you prefer. The duration the light comes on for can also be changed, to either one or three seconds.
This particular watch has Casio's `Multi band 6' technology, which allows it to calibrate itself from a signal from any of six atomic transmitters dotted around the world (we have two to choose from, in both England and Germany, lucky us!) The calibration takes place automatically at unspecified times of the day, but if you find that it hasn't happened for whatever reason, then you can always perform a manual calibration, which only takes a couple of minutes depending on the strength of the signal. Casio recommend that you point the 12 o'clock position of the watch in the direction of your nearest transmitter when calibrating, as the watch's antenna is located at this position.
My version of the PRW-2500 came with a solid titanium wrist band that looks great and is extremely light. It's not, however, indestructible and it does scratch quite easily, so if you intend roughing it with your watch then you may want to consider the resin or fabric-banded versions. Unfortunately, unlike the band, the case feels like plastic but Casio's website tells me that it is resin; there may be a good reason for not making it out of titanium as well, but only Casio themselves can answer that.
You'd think that there was only so much technology that Casio could pack into a watch but in my opinion they've done an admirable job here, while keeping the package small and fairly classy. As with any outdoors-oriented techno-watch, you have to take the sensor readings with a pinch of salt - and you should never rely on them for your survival - but as a tool for basic outdoors work this one seems hard to beat.