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What is the difference between a GPS watch and a GPS watch with barometer?

Key differences


Suunto GPS watches with barometer like Suunto 9 Baro, Spartan Sport Wrist HR Baro, Spartan Ultra, Ambit3 Peak, Ambit3 Vertical, Suunto Traverse and Traverse Alpha:

  • Have a built-in pressure sensor which measures ambient air pressure producing barometric altitude measurements
  • Barometric altitude gives more accurate altitude information and ascent/descent values by combining GPS data with barometric altitude information (FusedAltiTM).
  • A watch with barometer can display outdoor-related insights like sea level air pressure, and storm alarm.
  • Can display altitude information as part of the watch face in time mode.

Learn more below.


Suunto GPS watches like Suunto 9, Suunto 5, Spartan Sport Wrist HR, Spartan Sport Trainer Wrist HR, Spartan Sport, Ambit3 Run:

  • Calculate altitude and altitude changes (ascent / descent) based only on GPS information.
  • Cannot show outdoor insights like sea level air pressure, and storm alarms that require a barometer.

Learn more below.



Suunto GPS watches with barometer

How do GPS watches with barometer measure altitude and altitude changes (ascent/descent)?

GPS watches with barometer measure ambient air pressure to calculate altitude and altitude changes. In general, air pressure gets lower when ascending and gets higher when descending.

The watch calculates your current altitude based on:

  • Your surrounding air pressure AND
  • A known altitude reference value

Without setting an altitude reference value (known altitude, sea level pressure or Auto Adjust using FusedAltiTM depending on your watch), the altitude reading will not be correct. Learn more about how to set an altitude reference value in the user guide for your product .

After setting the altitude reference value, changes in altitude will affect the altitude reading. Please note, as well changes in weather conditions affect the altitude reading. Thus, the watch needs to be calibrated on a regular basis, especially during exercise (e.g. hikes). Watches with FusedAltiTM technology as Suunto 9 Baro and Spartan Sport Wrist HR Baro use the feature Auto Adjust to calibrate during exercise. Learn more in the user guide of your product under “Alti-Baro” or “Altimeter”.



What are the advantages of a GPS watch with barometer?


More accurate altitude information - FusedAltiTM

GPS watches with barometer use FusedAltiTM, a technology Suunto uses to combine GPS based altitude with barometric altitude. FusedAltiTM combines the benefits of both measurement methods and provides more accurate altitude readings and ascent / descent values when compared to watches with GPS only.

GPS based altitude measurement reacts slower to changes in altitude than barometer based altitude measurement, but the readings are not disturbed by weather changes as may be the case with barometric altitude readings. Barometric altitude is accurate and fast in reacting to fast altitude changes in terrain. FusedAltiTM utilizes the accurate and fast reacting profile of barometric altitude and uses GPS altitude to set the altitude reference for the profile.

Note: You need to calibrate your watch by setting an altitude reference point. Without regular calibration, the altitude readings may be wrong. Learn more in the user guide of your product under “Alti-Baro” or “Altimeter”.


Outdoor insights

GPS watches with barometer provide a storm alarm feature which is based on a significant drop in barometric pressure.


Altitude readings in time mode

The built-in barometer provides constant altitude information as part of the watch face in time mode whereas GPS watches only provide altitude information during exercise as the GPS is deactivated in time mode due to battery saving reasons.

GPS watch with barometer use an automatic alti/baro profile to determine if a change in air pressure is caused by a change in weather or change in altitude. The watch adjusts the altitude or sea level value based on this system. This way the altitude does not drift even if GPS and FusedAltiTM is not used when the watch is in time mode.



Suunto GPS watches

How do GPS watches measure altitude and altitude changes (ascent/descent)?

GPS watches base altitude information and ascent/descent values only on Global Positioning System (GPS) data provided by satellites orbiting Earth. The accuracy of the altitude information is highly dependent on the number of available satellites, the quality of the GPS signal and the defined GPS settings (for Suunto 9 and Suunto 5 battery mode) on your watch.

Note: Always choose GPS accuracy Best in your watch before starting an exercise.

For Suunto 9 and Suunto 5 the battery mode setting defines the GPS accuracy. For GPS accuracy Best, select Performance under Options > Battery modes before starting an exercise.
Learn more about “How do I get the most out of the battery modes?” and “How does GPS accuracy in battery mode impact the tracking of my exercise?”.

For Spartans scroll down to Options on the exercise start screen, select GPS accuracy and choose Best.
Learn more about the GPS accuracy in the user guide of your product under “GPS accuracy and power saving”.


Which factors affect the GPS signal quality?

The GPS signal strength is influenced by various factors and can - in a similar way as light - be partly or completely blocked by for example

  • trees
  • water
  • buildings
  • bridges
  • metal constructions
  • mountains
  • in gullies or ravines
  • thick, humid clouds

However, even under good signal conditions and with the best accuracy, GPS altitude should always be considered as an estimation of your real elevation.