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Strapdown Geonav - Geophysical Navigation Library

This crate provides geophysical navigation capabilities for strapdown inertial navigation systems, enabling gravity and magnetic anomaly aiding for improved navigation accuracy, particularly in GNSS-denied environments.

Overview

strapdown-geonav is a library crate that extends the basic strapdown navigation simulation by incorporating geophysical measurements (gravity and magnetic anomalies) to aid navigation.

Note: The standalone geonav-sim binary has been consolidated into strapdown-sim. Use strapdown-sim with the --features geonav flag to access geophysical navigation capabilities.

Usage

As a Simulation Tool

Build and run with geophysical navigation support:

# Build strapdown-sim with geonav feature
cargo build --release --package strapdown-sim --features geonav

# Run geophysical navigation simulation
strapdown-sim cl --input data.csv --output out/ \
    --geo \
    --gravity-resolution one-minute \
    --filter ukf

# Magnetic navigation
strapdown-sim cl --input data.csv --output out/ \
    --geo \
    --magnetic-resolution two-minutes \
    --magnetic-noise-std 150.0

As a Library

Add to your Cargo.toml:

[dependencies]
strapdown-geonav = { path = "../geonav" }

Use in your code:

use geonav::{GeoMap, GeophysicalMeasurementType, GravityResolution};
use geonav::{build_event_stream, geo_closed_loop_ukf};

// Load a gravity map
let measurement_type = GeophysicalMeasurementType::Gravity(GravityResolution::OneMinute);
let map = GeoMap::load_geomap("gravity_map.nc", measurement_type)?;

// Build event stream with geophysical measurements
let events = build_event_stream(
    &records,
    &gnss_config,
    Some(Rc::new(map)),
    Some(100.0),  // gravity noise std (mGal)
    None,         // no magnetic map
    None,
    None,
);

// Run simulation
let results = geo_closed_loop_ukf(&mut ukf, events)?;

Command Line Options

When using strapdown-sim --features geonav:

Enabling Geophysical Navigation

  • --geo: Enable geophysical navigation mode (required)

Gravity Configuration

  • --gravity-resolution: Map resolution (one-degree to one-minute)
  • --gravity-bias: Measurement bias in mGal
  • --gravity-noise-std: Noise standard deviation in mGal (default: 100)
  • --gravity-map-file: Custom map file path

Magnetic Configuration

  • --magnetic-resolution: Map resolution (one-degree to two-minutes)
  • --magnetic-bias: Measurement bias in nT
  • --magnetic-noise-std: Noise standard deviation in nT (default: 150)
  • --magnetic-map-file: Custom map file path

Common Options

  • --geo-frequency-s: Geophysical measurement frequency in seconds

Geophysical Map Files

Maps should be in NetCDF format:

  • Gravity maps: {input_name}_gravity.nc or specified via --gravity-map-file
  • Magnetic maps: {input_name}_magnetic.nc or specified via --magnetic-map-file

Map File Structure

Maps should contain:

  • lat variable: latitude coordinates (degrees)
  • lon variable: longitude coordinates (degrees)
  • z variable: anomaly data (mGal for gravity, nT for magnetic)

Example Scenarios

GNSS-Denied Navigation with Gravity Aiding

strapdown-sim cl --input urban_canyon.csv --output out/ \
    --geo --gravity-resolution one-minute \
    --dropout-start-s 0 --dropout-duration-s 999999

Intermittent GNSS with Magnetic Aiding

strapdown-sim cl --input flight_data.csv --output out/ \
    --geo --magnetic-resolution five-minutes \
    --sched duty --on-s 10 --off-s 40

API Documentation

See the Rust API documentation for detailed information on:

  • GeoMap - Geophysical map loading and interpolation
  • GravityMeasurement - Gravity anomaly measurement model
  • MagneticAnomalyMeasurement - Magnetic anomaly measurement model
  • build_event_stream - Event stream construction with geophysical measurements
  • geo_closed_loop_ukf / geo_closed_loop_ekf - Simulation functions

Performance Notes

  • Map Resolution: Higher resolution maps provide better accuracy but require more memory
  • Typical Noise Levels:
    • Gravity: 10-100 mGal standard deviation
    • Magnetic: 50-200 nT standard deviation
  • Coverage: Ensure geophysical maps cover the entire trajectory area