Add documentation for HDF5 data format support

Co-authored-by: jbrodovsky <57160841+jbrodovsky@users.noreply.github.com>

Author: Copilot

core/README.md

@@ -20,4 +20,54 @@ The toolbox is designed for research, teaching, and development purposes and aim
 
 The simulation program provides a simple command line interface for running various configurations of the INS. In can run in open-loop (dead reckoning) mode or closed-loop (full state loosely couple UKF) mode. It can simulate various scenarios such as intermittent GPS, GPS degradation, and more. The simulation is designed to be easy to use and provides a simple API for generating datsets for further navigation processing or research.
 
-Both `strapdown-sim` and `geonav-sim` include built-in logging capabilities using the Rust `log` crate. Library functions use log macros for diagnostic output that can be captured by any logging backend.
+Both `strapdown-sim` and `geonav-sim` include built-in logging capabilities using the Rust `log` crate. Library functions use log macros for diagnostic output that can be captured by any logging backend.
+
+## Data Formats
+
+The library supports both CSV and HDF5 file formats for input and output data.
+
+### CSV Format
+
+CSV is the default format for compatibility and ease of inspection. The library can read and write:
+- **TestDataRecord**: Input sensor data (IMU, GNSS, magnetometer, barometer) from apps like Sensor Logger
+- **NavigationResult**: Output navigation solutions (position, velocity, attitude, biases, and covariances)
+
+```rust
+use strapdown::sim::{TestDataRecord, NavigationResult};
+
+// Read CSV files
+let input_data = TestDataRecord::from_csv("sensor_data.csv")?;
+let results = NavigationResult::from_csv("nav_results.csv")?;
+
+// Write CSV files
+TestDataRecord::to_csv(&input_data, "sensor_data_out.csv")?;
+NavigationResult::to_csv(&results, "nav_results_out.csv")?;
+```
+
+### HDF5 Format
+
+HDF5 provides efficient storage for large datasets with better compression and faster I/O:
+
+```rust
+use strapdown::sim::{TestDataRecord, NavigationResult};
+
+// Read HDF5 files
+let input_data = TestDataRecord::from_hdf5("sensor_data.h5")?;
+let results = NavigationResult::from_hdf5("nav_results.h5")?;
+
+// Write HDF5 files
+TestDataRecord::to_hdf5(&input_data, "sensor_data_out.h5")?;
+NavigationResult::to_hdf5(&results, "nav_results_out.h5")?;
+```
+
+**HDF5 File Structure:**
+- TestDataRecord data is stored in a `/test_data` group
+- NavigationResult data is stored in a `/navigation_results` group
+- Each field is stored as a separate dataset within the group
+- Timestamps are stored as RFC3339-formatted strings
+
+The HDF5 format is particularly useful for:
+- Large datasets that benefit from compression
+- Integration with scientific computing workflows (Python, MATLAB, Julia)
+- Parallel I/O operations
+- Hierarchical data organization

core/src/sim.rs

@@ -1,12 +1,42 @@
-//! Simulation utilities and CSV data loading for strapdown inertial navigation.
+//! Simulation utilities and data I/O for strapdown inertial navigation.
 //!
 //! This module provides tools for simulating and evaluating strapdown inertial navigation systems.
 //! It is primarily designed to work with data produced from the [Sensor Logger](https://www.tszheichoi.com/sensorlogger)
 //! app, as such it makes assumptions about the data format and structure that that corresponds to
-//! how that app records data. That data is typically stored in CSV format and is represented by the
-//! `TestDataRecord` struct. This struct is fairly comprehensive and should be easily reusable for
-//! other applications. Modeling off of that struct is the `NavigationResult` struct which is used
-//! to store navigation solutions from simulations, such as dead reckoning or Kalman filtering.
+//! how that app records data. 
+//!
+//! # Data Structures
+//!
+//! - **`TestDataRecord`**: Input sensor data including IMU, GNSS, magnetometer, and barometer measurements
+//! - **`NavigationResult`**: Output navigation solutions including position, velocity, attitude, biases, and covariances
+//!
+//! Both structures support CSV and HDF5 file formats for input and output:
+//!
+//! ## CSV Format
+//! ```no_run
+//! use strapdown::sim::{TestDataRecord, NavigationResult};
+//!
+//! // Read and write CSV files
+//! let data = TestDataRecord::from_csv("sensor_data.csv").unwrap();
+//! TestDataRecord::to_csv(&data, "output.csv").unwrap();
+//!
+//! let results = NavigationResult::from_csv("nav_results.csv").unwrap();
+//! NavigationResult::to_csv(&results, "output.csv").unwrap();
+//! ```
+//!
+//! ## HDF5 Format
+//! ```no_run
+//! use strapdown::sim::{TestDataRecord, NavigationResult};
+//!
+//! // Read and write HDF5 files
+//! let data = TestDataRecord::from_hdf5("sensor_data.h5").unwrap();
+//! TestDataRecord::to_hdf5(&data, "output.h5").unwrap();
+//!
+//! let results = NavigationResult::from_hdf5("nav_results.h5").unwrap();
+//! NavigationResult::to_hdf5(&results, "output.h5").unwrap();
+//! ```
+//!
+//! # Simulation Functions
 //!
 //! This module also provides basic functionality for analyzing canonical strapdown inertial navigation
 //! systems via the `dead_reckoning` and `closed_loop` functions. The `closed_loop` function in particular