Meh, that's how these G-Shocks and Pro Trek's work. It comes with the territory, I guess. If you want more precision than this, you could get a GPS watch or really any "real" altimeter that doesn't rely on barometric pressure for its reading. What does bother me, though, is that, to my mind, once I manually input the altitude at my current location (using the adjust button when in Altimeter mode), a few hours later, my watch will have still magically moved by 30 meters (~100ft) even if I haven't. That is, the watch couldn't tell with 100% accuracy what is a change in pressure due to an altitude change and what is a real weather change. That really surprises me given that the technology it would take (an alti-lock) is already used in competitive watches, albeit more expensive ones. I do hope that CASIO addresses this weakness in the version 4 of its sensors (though it is probably not a sensor problem, but a programming one).
Until then, my advice is to manually correct the altitude shown by your watch whenever you have another reliable way of verifying your actual altitude (such as being at sea level, or at home, or any other place you can check on Google Earth). Then, for a short time -- until the weather changes -- your watch will show the right altitude as you climb up or down. At least every morning and every evening, as the barometric pressure changes, your watch will become unreliable again. Groundhog day, anyone?!
P.S. I don't really "need" this feature and if I did, I would use proper equipment, so my mild frustration with my Rangeman is a moot point that only a real nerd or an OCD-victim can understand and relate to.
An altidude lock as well as the sea-level-pressure is a very easy to programm task for an ABC watch and greatly helps to enhance accuracy (namely to lower or avoid drifts). Don't know why Casio still doesn't incorporated those in their watches. Considered, for how long one meter altimeter increments, altilocks and SPL are now on the market by LOTS of other companies, right now Casio shouldn't have V3 sensors, but probably V5 or V6...
It really doesn't matter to me anymore, since I gave up on Casio ABC's quite some time ago but the hardcore Casio fanboys can only hope that it doesn't take as long for altilocks and SLP as it took to make the first ABC G-Shock. The Rangeman is certainly a nice and very rugged watch but for the price they call for it, there are still too many flaws - at least for me. The most interesting thing for me about this watch is the shortcut to the STW, which is something that ironically only exists in analog chronographs usually. I certainly hope we will see other, more basic models with that feature in the upcoming future.
I have yet to receive my Rangeman, does it have sea level pressure or altitude reference settings or both like most ABCs? Zeroing it when you are at sea level does not help if you are not at that location all the time, hence the most accurate way to "calibrate" the altimeter is align it with GPS altitude as and when needed.
GPS is inacurate, that's why more expensive GPS systems also have a barometric Altimeter. The altitude changes are always relative, but, like on the Riseman and ProTreks you can set the correct altitude. For me, this is the same as zeroing, as I live at 0m.
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