FastFix Albatross Data: 4-ms Snapshots of Raw GPS L-1 data from Royal Albatross tracked over 1 month in New Zealand

This dataset consists of snapshots the RAW GPS L-1 baseband data from wildlife tracking tags deployed on Royal Albatross near Dunedin, New Zealand. Ten tags were recovered, and from these tags, 70,733 snapshots were stored. Each snapshot is a file FIXXXXX.BIN that contains a header, followed with interleaved 1-bit I/Q data sampled at 8.184 MHz, mixed down to a frequency of 32000 Hz.

The tags are:
* AF18: 10060 snapshots
* AF29: 4135 snapshots
* AF14: 11054 snapshots
* AF31: 3337 snapshots
* AF13: 10801 snapshots
* AFF6: 1888 snapshots
* AF19: 1701 snapshots
* AFF7: 10865 snapshots
* AF17: 10814 snapshots
* AF15: 6078 snapshots

Raw Shapshot Directory Structure

Each tag data is located in a directory. In this is a file START_DATE.TXT that contains the starting date of the clock in the tag. This is stored in ISO UTC format. Within each tag directory are subdirectories that contain groups of 1000 snapshots.

Snapshot File Structure

The header consists of 6 32-bit binary integers which are (in order)

rtc_counter_value: Offset in seconds since the START_DATE.txt

sample_count: Number of Samples in this shapshot

sample_bytes: Number of bytes in this shapshot

sample_ms: Snapshot duration in milliseconds

sampling_rate: Sampling Rate

checksum: A checksum for validating that data.

data.....: the remaining interleaved 1-bit I/Q data.

Acquisition Data

In addition, a GPS satellite acquisition has been performed that retrieves the codephase and doppler shift from each of these files (where one or more satellites are visible). These are stored in a JSON file for each tag in the directory 'acquisition'. The following is an example of an entry that has three visible satellites.

    {
        "codephase": [
            0.9030530071552871,
            0.8163265306122449,
            0.7794026875695107
        ],
        "doppler": [
            1161.2103571268162,
            1060.6060606060637,
            -1829.8852286096371
        ],
        "infile": "/freenas/tag/albatross_data/AFF6/00/FIX00287.BIN",
        "rtc": 172502,
        "sample_ms": 4,
        "sampling_rate": 8183833,
        "sv": [
            3,
            6,
            16
        ],
        "x_max": [
            15.513610551034326,
            9.794986743010222,
            21.07684312237483
        ]
    }

FastFix Position Estimates

Processed animal tracks are available in the file fastfix_position_estimates.json. These are JSON formatted arrays of 2D positions (without altitude, as all positions were essentially at sea-level). These have been processed using the FastFix algorithm [https://doi.org/10.3390/s20226480] to recover estimates of the animals position.