ELLIPSE2 AHRS & INS
– Hardware Manual
ELLIPSE2HM.1.3
1.3.5. Internal barometric altimeter
The Ellipse-N and E models embed a MEMS pressure sensor, used as altimeter. This pressure sensor is fully
calibrated and temperature compensated making it ideal to measure accurately absolute pressure.
The Ellipse converts this absolute pressure into altitude using the Standard Atmosphere model, assuming a
constant temperature gradient over altitude, and a sea pressure level of 1013,25 hPa.
Barometer specifications
Pressure sensor
Specification
Remarks – Conditions
Resolution
1.2 Pa
10 cm resolution
Pressure accuracy
± 50 Pa
± 200 Pa
± 350 Pa
Relative – [25°C], 700...1100 hPa
Absolute – [0...50°C], 450...1100 hPa
Absolute – [-20...85°C], 450...1100 hPa
Long term stability
< 100 Pa/yr
Update Rate
100 Hz
1.3.6. External sensors
1.3.6.1. Third party GNSS receiver
The Ellipse-E model does not include a GNSS receiver, but can be connected to an external GNSS module. All
GNSS receivers will provide velocity and position aiding. In some applications such as automotive ones, the
GPS course can also be used as heading reference input.
Dual antenna systems can also provide a True Heading aiding. RTK GPS receivers can be used to improve
positioning accuracy.
1.3.6.2. Odometer
In addition to the GNSS aiding, the Ellipse-N and E versions includes an odometer input which can greatly
improve performance in challenging environments such as urban canyons. The odometer provides a reliable
velocity information even during GPS outages. This increases significantly the dead reckoning accuracy.
The Ellipse handles quadrature output or compatible odometers in order to support forward and backward
directions.
Note: Odometer integration is made really simple as the Kalman filter will finely adjust odometer's
gain and will correct residual errors in the odometer alignment and lever arm.
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