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How Receivers Store Data.docx
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How Receivers Store Data

Sensorgnome

Sensorgnomes can detect two types of transmitters: Lotek and CTT. These use fundamentally different methods for encoding their ID so require different methods processing their data. Data from each tag is stored in separate files, with Lotek tag detections described below.

Data are stored in folders, one for each day that data has been collected (naming format: “YYYY-MM-DD”). Inside each folder are a bunch of compressed text files with the file suffix ‘.tar.gz’. There will be one file for each hour of that day where the station was operating. Multiple files may exist for the same hour period when large number of radio pulses occur.

Clam_Bay-1614BBBK1919-000431-2019-07-02T22-50-08.9330T-all.txt

Deployment name-Serial number-Boot number-DateTTimeT-Part.txt

Each text file contains a list of ‘CSV’, or comma separated values which correspond to radio pulses and GPS fixes.  Four radio pulses make up a single tag ‘burst’ and contains the information needed to encode the tag ID. Detections of Lotek tags are logged on the Sensorgnome as individual pulses and must be uploaded to Motus servers for processing to decode tag IDs.

Lines beginning with ‘p’ followed by a number are radio pulses from different numbered USB ports.

p2, 1568126890.4553, -6.826, -70.1, -77.26

port, timestamp, frequency offset, Max signal strength, Min signal strength

Column Name

Description

port

USB port number antenna is plugged into

timestamp

Datetime in UTC, as received by satellite

Frequency offset

Difference in frequency from the nominal frequency (typically 166.380 MHz). Units are in KHz.

Max signal strength

Peak signal strength (in dB) of the detected radio pulse

Min signal strength

Base signal strength (in dB) of the detected radio pulse

Lines beginning with ‘G’ are GPS fixes.

G, 1554655039.085, 45.167473333, -61.454788333, 16.1

G, timestamp, latitude, longitude, altitude

Column Name

Description

G

Identifier for all GPS fixes

timestamp

Datetime in UTC, as received by satellite

latitude

Latitude of the GPS antenna (decimal degrees)

longitude

Longitude of the GPS antenna (decimal degrees)

altitude

Altitude of the GPS antenna (meters)

CTT Sensorstation

Sensorstations are based on Sensorgnome software and hardware and data are stored similarly. Sensorstations are capable of detecting signals from two different transmitter technologies which require different processes to decode their signals. Lotek transmitters are logged identically to SensorGnomes, but in a separate folder from detections of the other transmitter type. CTT transmitters are logged with their ID decoded, unlike Lotek transmitters. Data is downloaded as CSV files, with one file for each hour that data was collected. Filenames include the device serial number as well as the date and time the file was created:

CTT-867762040716513-data.2019-11-23_152613.csv

Serial Number-Source.Date_Time.csv

 GPS hits are separated into another file with the same name but with the label ‘gps as the ‘Source’ part of the file name.

data files are stored with five columns and include the headers:

Time,RadioId,TagId,TagRSSI,NodeId

Column Name

Description

Time

Datetime in UTC

RadioId

ID of the receiver module (integrated or USB dongle)

TagId

Decoded tag ID

TagRSSI

Received signal strength indicator (dB)

NodeId

SensorNode ID, if applicable

gps files are stored with five columns and include the headers:

recorded at,gps at,latitude,longitude,altitude,quality

Column Name

Description

recorded at

Datetime in UTC, when record was saved to memory

gps at

Datetime in UTC, as received by satellite

latitude

Latitude of the GPS antenna (decimal degrees)

longitude

Longitude of the GPS antenna (decimal degrees)

altitude

Altitude of the GPS antenna (meters)

quality

Numeric indicator of quality of GPS fix

Lotek SRX-series

SRX-series receivers are only capable of detecting Lotek’s tags, but they contain superior filters which reduce the number of false positives which are recorded. Sensorgnomes were designed as a low-cost version of Lotek’s devices, but they log data very differently.  Lotek’s receivers decode the signal they receive in-unit so they an log these ID’s instead of the raw radio pulses. All data is stored in a single file which does not have a specific file name structure. The file contains both tag detections and metadata associated with the receiver and changes to its parameters. Note that there is no timezone setting here even though it’s possible to change the timezone. For this reason, it’s important to be extremely cautious about timezones and ensure it’s always set to UTC.

This file begins with one or more sections for each time parameters were set or change. Each section includes information about these parameters and changes. A table of tag detections follow these sections, starting with detections that don’t have GPS fixes followed by those that do.

Column Name

Description

Date

The date in the timezone set by user

Time

The time in the timezone set by user

Channel

Not used

Tag ID

The manufacturer’s tagID

Antenna

The antenna number the tag was detected on

Power

The power of the received signal. (A number 0-255 with 255 being the maximum)

Latitude

Latitude of the GPS antenna

Longitude

Longitude of the GPS antenna