Riseman barometer/altimeter/altitude readings (again!)

Thread: Riseman barometer/altimeter/altitude readings (again!)

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  1. #1
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    Riseman barometer/altimeter/altitude readings (again!)

    I've done a search and read lots of posts on this (especially from seemingly anti-G-Shock Sunto owners! ) but can anyone explain the whole thing as I'm still confused.

    My local altitude is 100m and yesterday (wearing the watch on my wrist) the watch matched this to within 5m. Taking a walk down hill to town and back it reflected the change and once home again came back to 105m - all good. But last night I noticed the alti was reading at 90 or so and varied later - the watch was off my wrist most of this time. This morning it read 50m and now on my wrist 1/2 hour later it is showing 30m!? Took it off for 15 mins and another reading gives 45m. Obviously during the day, night and this morning the temperature changed from say (on wrsit) 27 deg C to this morning (on table) 21 deg C.

    Pressure last night was around 1005mb but this is reading 1010mb this morning.

    On the barometer graph the reading at 8am is 3 dots above the one at 6am but I don't think the pressure has hardly moved in that time!

    The barometer graph is up and down with dots here and there sometime - not the nice gentle 'line' that I have seen.

    Is all this normal?? Can anyone explain how it's algorithms work with regard to temp/pressure/alt and how much of a deg/mb change should affect another reading.

    Never had an ERR reading for the A/B functions.

    Anyone had a faulty Riseman or compared one sitting next to another?
    Last edited by Max...; September 19th, 2012 at 10:09.

  2. #2
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    I don't own a riseman but I have owned a few Pathfinders. The difference in altitude is caused by the change in barometric pressure. The altimeter uses the pressure sensor to measure altitude. A rise in barometric pressure will cause the altitude to show lower and vice versa. I do own a suunto core which works in the same manner but the core has an auto setting which allows the watch to switch to barometer when you are stationary and to altimeter when you begin moving. This allows for a little better accuracy (I may be wrong) but most ABC watches will show some error due to these changes. For best accuracy I believe one has to adjust occasionally whether its the altitude or the barometer reading. It doesn't sound like it is malfunctioning but I'm no expert and there are some on here who may be able to answer it better than I have. And by the way I am a big Casio fan who just happens to own a Suunto. ;)
    Cheers

    Sent from my Desire HD using Tapatalk 2
    Last edited by davehb2001; September 19th, 2012 at 09:27.

  3. #3
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    Re: Riseman barometer/altimeter/altitude readings (again!)

    Also, the baro/alti sensor used by Casio isn't thermo compensated - so when you take the watch off and it cools down, the baro reading changes. The approximate relationship between temp and reading is in a printed table at the back of the manual. Suuntos, on the other hand, have compensated sensors, and have had for many years. Much as I like my Riseman, it's about time Casio updated their barometric sensor technology.

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  5. #4
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    Re: Riseman barometer/altimeter/altitude readings (again!)

    It's rather simple. When you go into ALTITUDE mode, your watch measures barometric pressure and then shows the value of altitude which corresponds to the pressure reading. It has a table of values similar to this one(Air Pressure and Altitude above Sea Level) stored in the memory.
    But barometric pressure is influenced by other factors as well, such as weather conditions or temperature. Read this: CHANGES IN ATMOSPHERIC PRESSURE
    The watch doesn't filter out these influences. Besides that, the baro sensor measures air pressure with a certain degree of error in the first place. So in the end all these errors add up and sometimes you get a not so good reading of altitude.

    To put it a bit more clear: in ALTI mode the watch measures air pressure. The pressure reading it gets is the result of altitude + weather conditions + temperature + sensor error + anything else that may influence the air pressure and/or the reading. Then it takes that pressure reading and puts it through a table of values similar to what you see in the first link. It acts as if only altitude had an influence on that reading, when in fact that is not true. That's where you get the difference from. Of course you may get a perfect altitude reading too, but that happens only when the influence of the other factors is negligible.

    Hope it's clear.

    Cheers, James
    Last edited by watch1000; September 19th, 2012 at 20:57.

  6. #5
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    Re: Riseman barometer/altimeter/altitude readings (again!)

    Thanks guys, great posts. Happier now for a few reasons - the explanations above but also I went out for a MTB ride yesterday and it matched the many climbs/descents (+/- 50m up and down really accurately). Lastly checking a few times over the day against our local official weather station air pressure reading (adjusted for sea level) it was within 0.5 mb. I guess at the end of the day this is probably a sub $10 manufacturing cost watch to Casio and for me is an amazing piece of kit for the brand new retail price of £114.

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    Re: Riseman barometer/altimeter/altitude readings (again!)

    Think they'll ever bring out a watch that goes off GPS and gives your altitude that way?

  8. #7
    LUW
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    Re: Riseman barometer/altimeter/altitude readings (again!)

    Quote Originally Posted by cosmo3k View Post
    Think they'll ever bring out a watch that goes off GPS and gives your altitude that way?
    Suunto Core.
    Cheers!
    Luciano

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