Knight Systems

GINI Features and Specifications

Land, air, sea.
GPS/INS tight coupling, loose coupling, transfer-alignment, fine gyrocompassing, INS-only and GPS-only navigation.
Real-time, near real-time, and post-processing.
Gyro quality 0.001° /hr to 30° /hr. Optimal solution given the sensors.

Navigation outputs at any rate up to IMU DV, Dq rate.
Formats -- lat/lon, ECEF, range coordinates, speed/track/climb, East/North/Up velocity, roll/pitch/heading, attitude direction cosines.
All valid at last data capture event, receiver measurement, navigation cycle, or time you specify
Solution referenced to point on vehicle.
Equations of motion use exact, ellipsoidal, rotating earth model of World Geodetic System, 1984.
Wander azimuth mechanization.
Sculling compensation when required.
Bortz attitude formulation.

20-State Core -- position, velocity, tilt/azimuth, gyro and accel bias, clock effects, lever arm.
Measurements processed -- range, delta range, position, velocity.
Multiple GPS antennas and lever arms.
Bierman U-D mechanization.
Cholesky covariance propagation.
Filter cycle adapts to processor load.
Full state transition model describes evolution of navigation effects -- Schuler 84-minute loop, Coriolis terms, Earth 24-hour loop, higher-order.
Process noise model Q calculates dozens of distinct error components, using dynamics and sensor orientation, (instead of lumping effects together.)
Tolerant of non-linearities and poor a-priori assumptions. Will converge with initial azimuth error of 60 degrees.
Can initialize from raw measurements.
Multiple players.

Range, range rate at 0.5 Hz.
Range acceleration DV^r, typically at 100 Hz.
Adding together a long string of DV^r gives GPS Doppler at any given time.
Typical latency is 30 milliseconds.
Up to 12 satellites at once. Up to 10 antennas.
Algorithm accuracy: 0.2 Hz, typical, after adding up 4 hours of DV^r. (The entire error budget is allocated to INS, oscillator stability, and residual SA.)
Aiding is smooth. Receiver doesn’t even see the cutover to new ephemeris.

Computes satellite positions.
Range computations include satellite clock error, equipment group delay, relativistic effects, tropospheric delay, and lever arm, per ICD-GPS-200.
Checks raw ephemeris for errors.
Maintains a library of packed ephemeris, current and preceding issue, for all satellites.
Maintains unpacked ephemeris for up to 12 satellites at once.
Accepts raw ephemeris in ASCII or binary, 8 or 10 words per subframe, and permuted or natural byte order. Also accepts floated ephemeris.

Accept or reject measurements based on measurement error and standard deviation.
Verify self-consistency of measurement batch.
Cancel a measurement batch after it has already been processed.
Estimate measurement accuracies.
Functions return status codes.
Safety lockouts for function sequences.
Dilution of precision calculations (PDOP).
Compare GPS-only to GPS/INS.
Monitor the filter accuracy estimates, correction magnitudes, and sensor bias estimates.

Re-play mission twice; The system acts the same on both passes, except that all second-pass results are smoothed.
Achieving 10 cm accuracy with some systems.

Modules involved with analytical computations all include built-in self test.
A complete GPS/INS simulation is built into GINI in order to verify operation when moved to a new environment.

Real-time navigation typically requires 1.3% of computing capacity of a 120 MHz Pentium.
Requires 136 Kb for code and data, a 5 Kb stack, 33 Kb heap, plus 31 Kb heap per player.

26,000 lines of source code.
Uses a subset of plain C, compatible with Microsoft, Borland, and ANSI C and C++.

Not just a navigation filter, it's a whole concept.
GPS and INS suppliers are able to participate in an optimal integration without understanding the other components, or their integration.
Flexible finished product; substitute other sensors in response to evolving requirements, new technologies, changing markets, changing availability and price.
Permits evolutionary approach to system development.
Greater reliability of finished product.
Backup navigation modes in case of component failure.
Simple. In a prototype demonstration, (without receiver aiding,) a single wire was all that was necessary to connect the GPS receiver and INS. Integration and van test was accomplished in a matter of days.
Flexible timing structure -- GPS, INS can be synchronous or asynchronous.

Requirements of INS or IMU to be Compatible

Self-moding and control after application of power.
Generate and output conventional DV, Dq, (delta-V and delta-theta: change in velocity and angle).
Sample DV, Dq simultaneously at regular epochs, typically 100 Hz or higher.
Compensate DV, Dq as necessary to achieve the advertised accuracy.
Support time tagging of DV, Dq epochs with GPS time, generally to within a small fraction of a millisecond.

Able to navigate autonomously.
Measure pseudoranges and carrier phase simultaneously at regular epochs, typically 1 Hz.
Output pseudoranges, carrier phase, ephemeris, position, velocity, accuracy statistics, status.
Time tag receiver data, and support time tagging of INS data, with GPS time.
Allow receiver clock to float.
If the receiver will be INS-aided, then make provision for applying GINI^®-computed signal Doppler, and for adjusting receiver bandwidth to accommodate INS error.