What's the difference between air pressure and GPS altitude?

The CS500+ training computer measures altitude with an atmospheric air pressure sensor and convert the measured air pressure into an altitude reading.

Air pressure sensor
  • This is the most accurate way to measure altitude and altitude changes (ascent / descent) after calibration.
  • To ensure that the altitude remains accurate, it needs to be calibrated whenever a reliable reference, such as a peak or a topographic map, is available or when at sea level. Calibration can also be set to automatic. This is especially useful if a training session is always started in the same environment.
  • Pressure variations due to weather conditions, or indoor air-conditioning, may affect altitude readings.
  • This is the most accurate way to measure altitude without calibration. Accuracy compared to calibrated air pressure sensor is +/- 10 m.
  • To show altitude at the beginning of a training session, the training computer needs to be connected to a minimum of 6 satellites. During training, the number of connected satellites can be fewer but if the number goes down to 0, RC3 GPS will again need a minimum of 6 satellites to re-establish altitude. To check the number of visible satellites, press and hold LIGHT in training mode to enter the Quick menu. Then select GPS info.
  • Due to the nature of the GPS signal, for example cliffs, tall buildings, and trees may block the satellite signal. Rain, fog, and snow may also affect the signal quality.

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