Two types of log files are created in auto_rx/log:
- 'System' Log files, which log things like scan results and errors. By default these are not written, but can be enabled using the --systemlog command-line argument. If enabled, these are written to
log/<timestamp>_system.log, where the timestamp is set based on when auto_rx.py was started. - 'Sonde' Log files, which log radiosonde telemetry on a per-sonde basis. These are written to
<timestamp>_<serial>_<sondetype>_<frequency>_sonde.log, where timestamp is the first time the sonde with a given serial number was heard. These are in a simple CSV format described below.
If running auto_rx via systemd, then all log messages are also written to /var/log/syslog, which is automatically rotated to save disk space. The auto_rx specific messages can be extracted from this log file using:
$ cat /var/log/syslog | grep auto_rx
Sonde Log Format
The sonde log files are in comma-separated-value format, with the following fields: 2020-06-07T11:49:45.001Z,R4930630,8242,-34.74629,138.53447,9666.5,2.7,25.4,46.2,-46.6,27.0,RS41-SG,401.500,31.1,750,10,2.8,-1,-1
| Field Number | Description | Example | Comment |
|---|---|---|---|
| 0 | Date / Time | 2020-06-07T11:49:45.001Z |
ISO-8601 format |
| 1 | Serial Number | R4930630 |
|
| 2 | Sequence Number | 8242 |
Ideally this number should be monotonically increasing throughout a flight, but some sonde types use a fairly short field, and will rollover during flight. |
| 3 | Latitude | -34.74629 |
Decimal Degrees |
| 4 | Longitude | 138.53447 |
Decimal Degrees |
| 5 | Altitude | 9666.5 |
Metres (most likely above-mean-sea-level) |
| 6 | Ascent Rate | 2.7 |
Metres/second |
| 7 | Ground Speed | 25.4 |
Metres/second |
| 8 | Heading | 46.2 |
Degrees True |
| 9 | Temperature | -46.6 |
Degrees Celsius |
| 10 | Relative Humidity | 27.0 |
Percentage (Note - the humidity calculations for most sondes are fairly crude, so should only be considered accurate to maybe 10% ). |
| 11 | Sonde Type | RS41-SG |
The radiosonde type and/or sub-type (e.g. RS41-SGM, DFM17). |
| 12 | Frequency | 401.501 |
Decoder centre frequency in MHz. |
| 13 | SNR | 26.7 |
Eb/N0 Estimate from the fsk_demod decoder, in dB. |
| 14 | Frequency Error | 750 |
Estimated signal offset from the decoder centre frequency, in Hz. |
| 15 | Num SVs | 10 |
The number of satellites used in the sonde's GPS solution. |
| 16 | Burst Timer | 08:21:15 |
RS41 Only - The time (HH:MM:SS) until the sonde will shut off, from either a 'burst timer' (shutdown X hours after burst), or 'kill timer' (shutdown X hours after launch). |
| 17 | Aux Data | 00AABBCC..... |
Hexadecimal data from any attached auxiliary sensors (e.g. Ozone, Radiation) |
Fields that do not have data available will be set to a nonsense value, e.g. -273 for temperature, -1 for humidity, -99 for SNR.
Log Processing Utilities
The following utilities are available to process the sonde log files generated by auto_rx.
Log File to KML
Within auto_rx/utils/ is the log_to_kml.py script, which can be used to process the sonde log files and convert them to KML.
This script requires the 'fastkml' and 'shapely' libraries, which can be installed using
$ sudo pip install fastkml shapely
Usage of this utility is as follows:
usage: log_to_kml.py [-h] [-i INPUT] [-o OUTPUT] [--clamp] [--noextrude]
optional arguments:
-h, --help show this help message and exit
-i INPUT, --input INPUT
Path to log file. May include wildcards, though the
path must be wrapped in quotes.
Default=../log/*_sonde.log
-o OUTPUT, --output OUTPUT
KML output file name. Default=sondes.kml
--clamp Clamp tracks to ground instead of showing absolute
altitudes.
--noextrude Disable Extrusions for absolute flight paths.
--lastonly Only plot last-seen sonde positions, not the flight
paths.
For example, to process a single log file, you would call:
$ python log_to_kml.py -i ../log/path_to_log_file_sonde.log -o output.kml
You can use wildcards in the input file argument, (i.e. ../log/*_sondes.log), however these must be wrapped in quotes, else bash will auto-expand the wildcard into a list. For example:
$ python log_to_kml.py -i "../log/*_sonde.log" -o output.kml
Producing Soundings ('SkewT' Plots)
A Python script is available in the auto_rx/utils directory to produce SkewT plots from auto_rx sonde log files. Refer to the script header for more information: https://github.com/projecthorus/radiosonde_auto_rx/blob/master/auto_rx/utils/plot_sonde_log.py