How does the ALTI function work and why is it so inconsistent??
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Thread: How does the ALTI function work and why is it so inconsistent??

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  1. #1
    Member StephenWatch's Avatar
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    How does the ALTI function work and why is it so inconsistent??

    I have been confused for several weeks now on the readings I get from my ALTI setting on my GWG1000. The BARO setting is 100% in agreement with the BBC weather site to the exact digit shown on there website, anything from 995 to 1028 so far. However, the ALTI geographical number for my home is 106m (348ft) according to local OS maps, but everyday it is different in wildly large amounts.

    This morning apparently I now live at -37m (-121ft) but has also read as high as 224m (734ft). I have manually adjusted it more than once to my home level 106m, but it just doesn't display any degree of consistency.

    If the BARO setting is accurate, what makes the ALTI setting vary so much, and if it is linked to pressure, what actual use is it to tell what level above/below sea level you actually are?
    Never argue with an idiot - they'll only bring you down to their level and win from experience...



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  2. #2
    Member domoon's Avatar
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    Re: How does the ALTI function work and why is it so inconsistent??

    there's no altimeter sensor on g-shock. on a triple sensor watches, the sensors are usually compass barometer and thermometer. altitude is estimated by barometer reading. the altimeter is not used when staying in one site. it's mostly used when u go hiking/climbing by calibrating the altitude on the base/first post of the mountain then u can check how far u've ascend/descend based on barometric change later - if the weather are relatively stable. sudden weather change might throw the altimeter reading off too.
    that's why if you only use it to check altitude in one location, it won't show constant value. it'll depend on the air pressure of the day. it's all in the manual BTW ;)
    Marrin and Time4Playnow like this.

  3. #3
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    Re: How does the ALTI function work and why is it so inconsistent??

    Yup just like he said, the altitude is calculated based on baro reading which means that it will vary depending on the weather even if you are stationary.
    This is why Suunto has something called ALTI LOCK, where you can lock the altitude if you are stationary so when you start to move you unlock it and don't need to recalibrate it every time.
    Despite that flaw, when it comes to reading altitude CHANGE the precision of the Casio algorithm is beyond this world, I simply cannot imagine that the watch can sense a difference in pressure in 1m increments!!
    I did a video with the Rangeman tied to a DJI MAVIC and it was VERY accurate showing the exact altitude that was shown on the Mavic that uses gyro sensors and GPS.

    here's a video



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    SgtPepper, jcombs1, domoon and 3 others like this.

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  5. #4
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    Re: How does the ALTI function work and why is it so inconsistent??

    I have noticed the altitude to be wild on normal days here there, but I don't really need to use then. If I calibrate the Baro and altitude out camping and hiking off active baro via interweb for area and national forest elevation marker. I keep it on altitude, to the next marker it's within 5 to 10m pretty accurate for such a small device I think.


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  6. #5
    Member MrDagon007's Avatar
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    How does the ALTI function work and why is it so inconsistent??

    Going forward, ideally the gps equipped models would use gps signals to determine the elevation, in principle it is possible to determine when the gps can receive 4 sattelites.

  7. #6
    Member Time4Playnow's Avatar
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    Re: How does the ALTI function work and why is it so inconsistent??

    Quote Originally Posted by Marrin View Post
    Yup just like he said, the altitude is calculated based on baro reading which means that it will vary depending on the weather even if you are stationary.
    This is why Suunto has something called ALTI LOCK, where you can lock the altitude if you are stationary so when you start to move you unlock it and don't need to recalibrate it every time.
    Despite that flaw, when it comes to reading altitude CHANGE the precision of the Casio algorithm is beyond this world, I simply cannot imagine that the watch can sense a difference in pressure in 1m increments!!
    I did a video with the Rangeman tied to a DJI MAVIC and it was VERY accurate showing the exact altitude that was shown on the Mavic that uses gyro sensors and GPS.

    here's a video



    WatchGeek YT Channel

    You got it!! Some time back, I would take an elevator in a parking garage every day. I used my Rangeman while in the elevator, resetting the alti value to zero before using the elevator (not the main reading but the...other feature, I forget its actual name). It was wild - it showed me the change in meters from the ground floor to the top, while riding the elevator!! It was very cool.
    Miklos86, domoon, Worker and 1 others like this.

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