**APPENDIX 3:**** Sensor Sampling and an Example Argos Message Format**

**
Sensor Sampling and Duty Cycle**

**
Atmospheric Pressure**

The format described here was used during deployments that tested pressure readings from both the AIR sensor and Kavlico sensor. The Kavlico sensor is not currently used. However, the de-spiking algorithm **is** the current version.

160 pressure samples (taking approximately 160s) are collected each hour. The de-spiking algorithm is as follows:

• Take the median of the lowest 10 points of 160

• Calculate the median of the points within the entire set of 160 points that are within 1hPa of the 10 point median

• Store as 12 bit count: 0 => 800.0 hPa and 4095 => 1209.5 hPa, with a 0.1 hPa resolution

• If 15 or more of the 160 samples include communication errors, the sampled set is deemed corrupt, and the transmitted count is set to zero

Historical pressure data are also stored for 24 hours. In the information that follows, time elapsed relative to most recent pressure sample (P1_{i}) is denoted by a subsript. For example a P1_{i-8} pressure sample is the pressure sample that is 8 hours older than the current pressure, P1_{i}.

**Sea Surface Temperature (SST)**

SST is sampled continuously with a 15-minute repeat cycle.

• Interval between samples = 60s

• Number of samples averaged = 15

• Number of thermistors monitored = 1 (YSI 44018 or equivalent)

• Store as 10 bit count

**Salt Water Switch**

The salt water switch is sampled continuously with a 30-minute repeat cycle.

• Length of salt water switch data collection = 30 minutes

• Store as 8 bit count = immersion time (in seconds) ÷ 10

**Duty Cycle**

Drifters should have option to be on **i** houra followed by **j** hours off where:

0 hours < **i** < 72 hours

0 hours < **j** < 72 hours

and **i** & **j** are both integers

**Transmitter Repetition Rate**

90s ± 10%

**Example Argos Message Format**

This example transmits a repeating sequence of four Argos messages. Each message, 256 bits long, contains the most recent sensor data as well as historical pressure data. The ensemble of four messages allows the previous 24 hours of pressure data and times of observation to be reconstructed.

**Description of Terms**

P1_{i} (12 bits)

P2_{i} (12 bits)

SST (10 bits)

Drog (8 bits)

Bat (2 bits)

Age (12 bits)

Sum_{i} (4 bits)

Sum (8 bits)

MessageID (12 bits)

CommError (2 bits)

HdrSum (4 bits)

**Transmission 1 (256 bits)**

Sum (8 bits), P1_{i} (12 bits), SST (10 bits),

P2_{i} (12 bits), MessageID (12 bits),

Drog (8 bits), Bat (2 bits), Age (12 bits),

P1_{i-4} (12 bits), P2_{i-4} (12 bits), Sum_{i-4} (4 bits),

P1_{i-8} (12 bits), P2_{i-8} (12 bits), Sum_{i-8} (4 bits),

P1_{i-12} (12 bits), P2_{i-12} (12 bits), Sum_{i-12} (4 bits),

P1_{i-16} (12 bits), P2_{i-16} (12 bits), Sum_{i-16} (4 bits),

P1_{i-20} (12 bits), P2_{i-20} (12 bits), Sum_{i-20} (4 bits),

P1_{i-24} (12 bits), P2_{i-24} (12 bits), Sum_{i-24} (4 bits),

CommError (2 bits), Unused (6 bits), HdrSum (4 bits)

**Transmission 2 (256 bits)**

Sum (8 bits), P1_{i} (12 bits), SST (10 bits),

P2_{i} (12 bits), MessageID (12 bits),

Drog (8 bits), Bat (2 bits), Age (12 bits),

P1_{i-3} (12 bits), P2_{i-3} (12 bits), Sum_{i-3} (4 bits),

P1_{i-7} (12 bits), P2_{i-7} (12 bits), Sum_{i-7} (4 bits),

P1_{i-11} (12 bits), P2_{i-11} (12 bits), Sum_{i-11} (4 bits),

P1_{i-15} (12 bits), P2_{i-15} (12 bits), Sum_{i-15} (4 bits),

P1_{i-19} (12 bits), P2_{i-19} (12 bits), Sum_{i-19} (4 bits),

P1_{i-23} (12 bits), P2_{i-23} (12 bits), Sum_{i-23} (4 bits),

CommError (2 bits), Unused (6 bits), HdrSum (4 bits)

**Transmission 3 (256 bits)**

Sum (8 bits), P1_{i} (12 bits), SST (10 bits),

P2_{i} (12 bits), MessageID (12 bits),

Drog (8 bits), Bat (2 bits), Age (12 bits),

P1_{i-2} (12 bits), P2_{i-2} (12 bits), Sum_{i-2} (4 bits),

P1_{i-6} (12 bits), P2_{i-6} (12 bits), Sum_{i-6} (4 bits),

P1_{i-10} (12 bits), P2_{i-10} (12 bits), Sum_{i-10} (4 bits),

P1_{i-14} (12 bits), P2_{i-14} (12 bits), Sum_{i-14} (4 bits),

P1_{i-18} (12 bits), P2_{i-18} (12 bits), Sum_{i-18} (4 bits),

P1_{i-22} (12 bits), P2_{i-22} (12 bits), Sum_{i-22} (4 bits),

CommError (2 bits), Unused (6 bits), HdrSum (4 bits)

**Transmission 4 (256 bits)**

Sum (8 bits), P1_{i} (12 bits), SST (10 bits),

P2_{i} (12 bits), MessageID (12 bits),

Drog (8 bits), Bat (2 bits), Age (12 bits),

P1_{i-1} (12 bits), P2_{i-1} (12 bits), Sum_{i-1} (4 bits),

P1_{i-5} (12 bits), P2_{i-5} (12 bits), Sum_{i-5} (4 bits),

P1_{i-9} (12 bits), P2_{i-9} (12 bits), Sum_{i-9} (4 bits),

P1_{i-13} (12 bits), P2_{i-13} (12 bits), Sum_{i-13} (4 bits),

P1_{i-17} (12 bits), P2_{i-17} (12 bits), Sum_{i-17} (4 bits),

P1_{i-21} (12 bits), P2_{i-21} (12 bits), Sum_{i-21} (4 bits),

CommError (2 bits), Unused (6 bits), HdrSum (4 bits)

Posted February 28, 1997

Sybrandy, A. L., C. Martin, P. P. Niiler, E. Charpentier, and D. T. Meldrum, 1995: