How To...

Altimeter

  1. Auto Calibration
  2. Barometer Mode
  3. Pressure Trending
  4. Plot Type
  5. Manual Calibration
  6. Weather Station
  7. Accuracy
  8. Altitude vs Elevation

 

 


1. Auto Calibration

  1. Choose when the altimeter is automatically calibrated
  2. Can be performed only while GPS signals are available (see Method #4 - Auto Calibration)
    • On (Auto calibration is enabled)
    • Off (Auto calibration is disabled)
    • Once (Altimeter is calibrated once per power cycle after satellite signal is available)
    • Continuous (Auto calibration is enabled)

 

 


2. Barometer Mode

  1. Choose a desired barometer mode
    • Variable Elevation (Allows the barometer to measure changes in elevation while you are moving)
    • Fixed Elevation (Assumes device is stationary and barometric pressure changes are only due to weather)

 

 


3. Pressure Trending

  1. Choose how the device records ambient pressure information
    • Save When Power On (records pressure only while the GPSr is powered on)
    • Save Always (wakes the device at 15 minute intervals to take pressure readings - useful when watching for pressure fronts)

 

 


4. Plot Type

  1. Elevation / Time (Record elevation changes over a period of time)
  2. Elevation / Distance (Record elevation changes over a distance)
  3. Barometric Pressure (Record barometric pressure changes over a period of time)
  4. Ambient Pressure (Record ambient pressure changes over a period of time)

 

 


5. Manual Calibration

  1. See Barometric Pressure and Altimeters
  2. Provides multiple methods for the user to calibrate the altimeter using a known value

 

 


6. Weather Station

  1. Use your barometric pressure sensor equipped Garmin GPSr to predict the weather
  2. This process requires the GPSr to remain stationary for an extended period of time (for example, after setting up camp for the evening)
  3. Tip: Create a dedicated 'Weather Station' profile pre-configured with the necessary settings for quick and easy access:
  4. Tip: Download and copy the weather prediction charts for your device to the [GPSr]\Garmin\JPEG\ or [microSD]\Garmin\JPEG\ directory, making them available for review in the field using the Photo Viewer on the GPSr
  5. After the GPSr has been placed outside and allowed to collect sufficient barometric pressure data, open the 'Altimeter' or 'Elevation Plot' page:



    		6.
    Barometric Pressure Data Plot
    		Select any position along data plot to view recorded value

  6. Predicting the Weather
    • Falling barometer values typically indicate clouding conditions that may result in rain
    • Climbing barometer values indicate the opposite, or clearing weather conditions
    • A barometric pressure variation greater than 0.18"Hg (6mb) in less than a three hour period is considered a rapid change
    • The longer it takes barometric pressure to change, the longer the coming weather pattern can be expected to last
    • It is possible that a small weather event, such as a passing shower, may not trigger any change in barometric pressure
    • Compare barometric pressure starting value with behavior to make a weather prediction:

    "Hg Rising or Steady Falling Slowly Falling Rapidly mb
    > 30.20 Continued Fair Fair Cloudy, Warmer > 1022
    29.80 to 30.20 Same as Present Little Change Precipitation Likely 1009 to 1022
    < 29.80 Clearing, Cooler Precipitation Storm < 1009


  7. Examples

    1. Continued Fair


    2. Fair


    3. Cloudy, Warmer


    4. Same as Present - Steady Rise from 29.81"Hg to 29.98"Hg over 17 hours
       

       

    5. Little Change - Slowly Falling from 29.99"Hg to 29.96"Hg over 13 hours
       
       

    6. Precipitation Likely - Rapid Drop from 30.07"Hg to 29.94"Hg over 4 hours
       
       

    7. Clearing, Cooler


    8. Precipitation


    9. Storm

 

 


7. Accuracy

 

 


8. Altitude vs. Elevation