Inertial Navigation System

1. Data Specifications:

The inertial navigation system is a north-oriented strapdown system with initial coordinates: longitude 116.344695283°, latitude 39.975172°, and altitude h=30 meters. The initial velocity v0=[0.000048637 0.000206947 0.007106781] remains constant throughout the flight duration. In code implementation, these initial parameters would typically be stored as constants or configuration variables in the navigation algorithm initialization module.

2. The jlfw dataset contains 600 seconds of flight data with both gyroscope and accelerometer sampling at 80Hz (sampling period = 1/80 second). This uniform sampling rate simplifies data synchronization and processing in the navigation algorithm, where sensor measurements are typically processed through digital filters and integration routines.

3. Initial attitude angles are specified as [0.120992605 0.010445947 91.637207] for pitch, roll, and heading respectively (in degrees). The jlfw file stores specific force measurements f_INSc (units: m/s²) and gyroscope angular rate measurements wib_INSc (units: rad/s). The data is organized with rows 1-3 representing east, north, and upward components respectively. This coordinate convention aligns with standard navigation frame representations and would be processed using direction cosine matrices or quaternion transformations in the attitude algorithm.

4. The heading angle uses counterclockwise as the positive direction convention, which is standard in navigation systems and matches mathematical convention for angle measurements.

5. Earth model parameters: Earth ellipsoid major radius re=6378245 meters, Earth rotation rate wie=7.292115147e-5 rad/s. Gravity acceleration is calculated using the formula: g = g0 * (1 + gk1 * c33^2) * (1 - 2 * h / re) / sqrt(1 - gk2 * c33^2), where g0=9.7803267714 m/s², gk1=0.00193185138639, gk2=0.00669437999013, and c33=sin(latitude). This gravity model implementation would typically be coded as a separate function taking latitude and altitude as inputs, accounting for Earth's oblateness and altitude effects in the navigation equations.

The gravity calculation formula incorporates Earth's shape parameters and altitude compensation. In practical implementation, this would be computed iteratively during the navigation solution, with c33 representing the sine of latitude used to calculate gravity variations due to Earth's geoidal shape.