16 September 2012

Altimeter watches

About 25 years ago, back when I did my first steps in mountaineering, altimeter watches were a rare thing. During those days the instrument of reference for altitude measurement and weather prediction was the analog altimeter.
Basically it was a aneroid barometer (quite similar to those I would find in the maritime industry years later, although smaller) with a regulable needle, to allow the calibration of the instrument to a known reference altitude (the condition needed to have accurate readings in the future).
Later came the digital altimeters (I remember the pioneering ones from Avocet, particularly their Vertech line) and the game rules started to change. The developments of electronics drove to achievements in miniaturization and, as a consequence, systems integration. And the first altimeter watches started to appear. But like every time when we are face to face with evolutions or revolutions, there's always that moment of doubt. Our conservative side. Dependent of the technologies that, regardless of being dated, we've learn to trust. Will it work? And more important than that... will it be reliable?
Well, my two cents worth on this subject is that what was new and doubtful twenty years ago is now a more than tested mainstream technology.
If there's a nation that can take Mankind's best technological ideas, make them even better, mass-produce them and sell them at a cheap price, it's Japan.
And in this particular market niche, due to its genial politics of functions integration, Casio was always on the lead.
So, when I bought my first altimeter watch, about ten years ago, among all the (few choices) on the market, the Casio brand was the most obvious. The company had, until then (still has), a record of well engineered, reliable and durable timepieces. So choosing Casio was a no-brainer.
Therefore I bought the Casio G-Shock DW-9100ZJ-1T Riseman. The G-Shock armour made the watch look ugly as Hell but also made me confident that it could withstand a nuclear explosion, if needed.
But since I bought it mainly for its altimeter function, my biggest question was: how accurate the altitude sensor was?
Didn't have to wait too long to find out. A few weeks after buying it, I was standing in the Torre plateau, in the Portuguese Serra da Estrela, at a geographic altitude of 1993 metres, and the watch on my wrist (still on factory calibration!!!!) was showing 1990 metres. Now, considering that the altimeter function in these watches is a sub-function of their barometric sensor and, therefore, the altitude of a given place is measured by the particular air pressure detected in that spot (which is hardly the same everyday), we have to take our hats off to the competence of the engineers that designed this product and to the perfection of the software included in it.
I was so amazed with that measurement, that I left it untouched on the watch memory for months. Just for the sheer pleasure of looking at it.
Honestly, you would have to use a Differential GPS to have better accuracy. Because the conventional one don't go nowhere as near.
A couple of years later, however, I had to change its battery for the first time. So I send it to the Casio repair centre in Lisboa. Together with replacement of the battery, they performed (mere routine) the hydrostatic test, to confirm its water tightness. And with that I lost its factory calibration forever. From then on, I would have to calibrate it manually, in a place with a known altitude, before starting my mountain activities. But, performed that procedure, the measurements remained always accurate.
Now, the watch is starting to show its age. First the watch band, due to the intense use, was damaged beyond repair. So I bought a new one. However, a few months after the band replacement, the bezel (made of some kind of rubberized plastic) started to crack itself near the sensor, the joints and in the more pressure subjected areas around the fixing screws. For that damage there is no easy repair, except replacing the entire exterior carcass. However, the watch is already discontinued for several years. And spares for it are not easy to find.
So, I've decided to buy a new one. Its younger brother: the Casio Riseman GW-9200J-1JF. This is, basically, the same watch. However, there are some major advances. It still is based on the same dual-sensor architecture: One sensor for atmospheric pressure and another one for air temperature. The altimeter, as I have said previously, is a sub-function of the barometer sensor. The new model, nevertheless, is a clear improvement of the old one's characteristics with the addiction of a few more. It's now a solar watch, so goodbye cell replacements; it's also a world timer, with a memory of up to 33 different time zones; it's an atomic time-regulated watch, meaning that (depending on the world region where you are) it can receive, automatically or manually and several times per day, a radio signal from reference stations, thus keeping the watch with an almost atomic precision.
For the outdoor use, the altimeter has now a range from -700 mts to 10000 mts (the early model had a range from 0 to 6000 mts), meaning that the barometer range was also extended (from 260 to 1100 mbar, contrary to the old model, which range was from 460 to 1100 mbar).
However, the thermometer of the new model is a little short (from -10º to +60º Celsius), when we compare it with the older one (from -20º to +60º Celsius). For outdoor activities, and in particular for mountaineering, this is not nearly enough. Minus ten degrees I have in the Portuguese mountains, during Winter time, and they are not, by any mountaineering standards, particularly cold. What would say about that a climber in the Alps, in the Rockies or in the Andes? This was clearly a step backwards, Casio. Why?
Meanwhile, while I was looking, searching the web for the Riseman's best price, I stumbled over a curious offer from Pulsar. Also a twin sensor watch, with temperature and pressure gauge, the Pulsar/Seiko PS7001 caught my eye. Cheaper than the Casio, this Alti-Thermo offer from Pulsar has a stainless steel bezel and, therefore, a more conventional (nevertheless elegant and stylish) look than the Casio. It's also a cheaper option. So I ended up buying both.
Yesterday, I went to the highest peak in Madeira to test their accuracy. After calibration of the two units at sea level, close to home, I hiked to the top of the island to check with my eyes the competence of these small wrist computers.
No surprise to me, they both performed very well. Both watches allow for manual calibration of the altimeter and thermometer functions. And that, as you might imagine, is quite important. The barometric sensor might become inconsistent with the aging of the equipment. It's not a defect. It's a technological reality. So, a sensor unable to be calibrated is useless in the long run. However, only the Casio watch has the ability of, besides the altimeter, manually calibrate (in full mb units)  the barometer function. In mountaineering activities, an exact barometer is not truly needed. As long as it's consistent, doesn't really matter if you have 1020 mb of pressure or 1010. The atmospheric pressure in the high mountains is completely different (lower, naturally!) than at sea level. And for weather prediction (supposing that you stay at the same altitude enough time - at least twelve hours -  to get sufficient data for interpretation) you just need to read the graph tendency: if the curve goes up (pressure rising), you will have good weather, if it goes down (pressure falling)... be aware.
However, I'm a professional mariner. And, for me, a barometer has to be exact. That's the reason why we send the ship's barometer and barograph every year ashore for calibration. To get, as much as possible, accuracy in readings. I'm prepared to accept five or six millibars of error as long as I know how much error do I have and if it is up or down. Much like the chronometers on board. They don't have to be exact. Actually, they never are. But we always know their errors. And the knowledge of that error makes a great difference in astronomical navigation.
So... that is a failure in the Pulsar that I cannot accept. On the positive side: the Pulsar data refreshing rate is faster, while the Casio is lazier. The Pulsar calibration is in full units (1596, 1597, 1598... etc) while the Casio altimeter is calibrated in multiples of five (1590, 1595, 1600... etc). Both units calibrate their thermometers in full units. To me, honestly, the multiples-o- five altimeter calibration in the Casio is not really an handicap. Like I've said before, you will be lucky, at any given place,  if you get a GPS accuracy for altitude of twenty meters. So, if you can get a precision of five meters with an alti-baro, we are already on the surrealist level.
In this point both units performed remarkably well.
So, in the end both are very interesting offers. The Pulsar is not as rugged as the Casio. It's a dressy Alti-Thermo. Looks nice, either with crampons or with a sporty suit. Its WR of 10 Bar is half of the Casio. Its altimeter only?! reaches 9000 mts, against 10000 of the Casio. And the displayed temperature (between 0 to 50º Celsius) is a tad more limited. On the other hand, the Casio is a legitimate heir of the G-Shock name. With a rugged design, you'll either like it or hate it. Environmentally speaking, it's a watch built for rough use. And abuse. And with a solar cell, it has the autonomy of a lifetime. For me, personally, if I had to be on the mountains everyday, I'd choose the Casio. Hands down. Surprisingly, on my daily near-the-sea-level routine I find myself grabbing the Pulsar quite frequently right after awakening.
Truth be told, you will be happy with either one.
The Casio Riseman GW-9200J-1JF and the Pulsar PS 7001, side by side in Madeira's highest peak (Pico Ruívo, alt. 1862 mts above sea level), showing their altitude measurements. Three meters error for the Casio and two for the Pulsar. Both units were calibrated at sea-level, several hours before. Sadly, since I don't have a precise meteorological thermometer, I wasn't able to check their temperature sensor accuracy.
Picture taken with Nikon D40X and Sigma EX DC 18-50mm f/2.8 Macro HSM, with Cokin Series P Linear Polarizer.
Post-processing in Adobe Photoshop CS3.