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Aiding Sensors
The Ellipse E, N, and D models offer an additional feature that can greatly enhance performance in difficult environments like urban canyons: an odometer input. This input provides reliable velocity information even when GNSS signals are unavailable, resulting in a significant improvement in dead reckoning accuracy.
To support both forward and backward directions, the Ellipse can handle quadrature output or compatible odometers. Additionally, the Ellipse can directly access the vehicle's odometer through the OBD-II connector (CAN bus odometer). These capabilities make the Ellipse an exceptional choice for autonomous vehicles, offering unparalleled accuracy even in harsh conditions.
Many different aiding sensors can be used to aid the Ellipse INS.
Internal Magnetometers
A set of three Anisotropic Magneto-resistive magnetometers is embedded within the Ellipse. This technology provides a very high sensitivity compared to coil based technologies.
Although part of the Ellipse internal IMU, the magnetometer is in fact considered as an "aiding sensor" and is not mandatory for proper operation.
Nevertheless, in many applications such as AHRS applications, airborne or several marine applications, this magnetometer is still a reliable and efficient way to observe heading.
Magnetometers require a specific in place calibration in order to compensate surrounding ferromagnetic materials and magnets. Please refer to the Magnetic Calibration page for more information about this.
Magnetometer sampling design makes it impossible to reject signal frequencies above 75Hz. User should ensure that high frequency noise is not disturbing magnetometers at the sensor's location.
| Specifications | Remarks | |
|---|---|---|
| Full scale (Gauss) | 50 | |
| Scale factor stability (%) | 0.5 | |
| Noise (mGauss) | 3 | Over 1 to 25 Hz band |
| Bias stability (mGauss) | 1 | |
| Bandwidth (Hz) | 22 | -3dB attenuation |
| Resolution (mGauss) | 1.5 | |
| Sampling rate (Hz) | 100 | |
| Orthogonality (°) | 0.1 | After user magnetic calibration |
Ellipse-N and Ellipse-D internal GNSS receiver
The Ellipse-N and Ellipse-D embed a high performance GNSS receiver (L1/L2 GPS, GLONASS, GALILEO, BEIDOU), capable of DGNSS, SBAS and RTK positioning.
The Ellipse-D also features a dual antenna heading delivering robust and accurate heading angle in the most challenging conditions. With a refresh rate of 5Hz, this receiver provides best accuracy and reliability in harsh GNSS environments. The standard RAW data output enables highest performance in post-processing applications.
| Item | Specification | Remarks / condition |
|---|---|---|
| Signal tracking |
| All constellations and signals enabled by default |
| Horizontal position accuracy | Single point: 1.5 m SBAS: 1.0 m RTK: 1 cm + 1ppm | |
| Velocity accuracy | 0.05 m/s | |
| Dual antenna heading accuracy | 0.55° (baseline > 0.5m) | Ellipse-D only |
| 0.4° (baseline > 1m) | ||
| 0.3° (baseline > 2m) | ||
| Time to first fix | Cold start < 24 s | |
| Output frequency | 5 Hz | |
| Differential corrections input | RTCM V3.x | Sent on any serial port |
Internal barometric altimeter
The Ellipse-E, N and D 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 | |
| Pressure accuracy | ±50 Pa | Relative - (25°C), 700...1100 hPa |
| ±200 Pa | Absolute - (0...50°C), 450...1100 hPa | |
| ±350 Pa | Absolute - (-20...85°C), 450...1100 hPa | |
| Long term stability | <100 Pa/yr | |
| Update Rate | 100 Hz |
External sensors
Third party GNSS receiver
The Ellipse-E/N/D models can be connected to an external GNSS module. All GNSS receivers will provide velocity and position aiding.
Dual antenna systems can also provide a True Heading aiding. RTK GPS receivers can be used to improve positioning accuracy.
The Ellipse-E, which doesn't have a built-in GNSS receiver, includes an additional connector (aux.) with more input/output ports to connect an external GNSS receiver.
While Ellipse-N and Ellipse-D can use an external GNSS receiver, they do not have the aux. connector and therefore the quantity of ports available is more limited. Keep this limitation in mind if you plan to use an Ellipse-N or Ellipse-D along with an external GNSS receiver.
For details on how to configure your Ellipse with an external GNSS receiver, check the Integrate an external GNSS page of the operating handbook.
Odometer
The Ellipse E, N, and D models offer an additional feature that can greatly enhance performance in difficult environments like urban canyons: an odometer input. This input provides reliable velocity information even when GNSS signals are unavailable, resulting in a significant improvement in dead reckoning accuracy.
To support both forward and backward directions, the Ellipse can handle quadrature output or compatible odometers. Additionally, the Ellipse can directly access the vehicle's odometer through the OBD-II connector (CAN bus odometer). These capabilities make the Ellipse an exceptional choice for autonomous vehicles, offering incredible accuracy even in harsh conditions.
Odometer integration is made really simple as the Kalman filter will finely adjust the odometer's gain and will correct residual errors in the odometer alignment and lever arms.
For details on how to configure your Ellipse with an odometer, check the DMI integration page of the operating handbook.
Doppler Velocity Log
The Ellipse E, N, and D models offer a DVL input as an additional feature to improve performance in challenging marine environments, such as areas under bridges or trees, in addition to GNSS aiding. The DVL input provides reliable velocity information even when GNSS signals are unavailable, leading to a significant improvement in dead reckoning accuracy.
The Ellipse handles the PD6 and Wayfinder protocols.
DVL integration is made really simple as the Kalman filter will correct residual errors in the DVL lever arms.
For details on how to configure your Ellipse with a DVL, check the DVL integration page of the operating handbook.