DBCP-M2-TEST Recommended format


(Meteo test - 28 bit Argos ID)


This Argos message format is based upon DBCP-M2 format and is used for test & evaluation purposes. See also complete list of DBCP recommended formats.

Table of contents

  1. Advantages
  2. Drawback
  3. Description
  4. Message format

ATTENTION: This format is used only for Argos messages transmitted using 28-bit Argos IDs. It is used for test and evaluation purposes.

Advantages of this format are:

Drawback:

Description

 

With 28 bit Argos IDs, first block of data is comprised of 24 bits;

Data are stored in the buoy memory in blocks of observations. Each block contains one single observation. Blocks are Block_Period minutes apart (e.g. every 30 minutes, every hour)). Normally, buoys are turned on at a round hour (e.g. 03h00) so that observations are made exactly at a round hour. However, this may not be the case and the on-board clock may drift in time. Transmitting the age of the observation at the time the message is transmitted to the satellite permits to recover the exact time of observation even in case the buoy real time clock has drifted.

One block (one observation) is transmitted in one Argos message. One Argos message contains only one block.

Hence, consecutive blocks can be transmitted using consecutive Argos messages using a transmission cycle. For example, if we pick a block_period of one hour, we could transmit the observations in a cycle of 3 Argos messages like this:

Block Rank
 
Block H 0
Block H-1 1
Block H-2 2
Block H 0
Block H-1 1
Block H-2 2
 
 

Rank is encoded in the Argos message. Rank of the most recent observation transmitted is 0. The rank of a given observation is incremented each time a new observation is carried out.

Age of the observation at the time of the next block update (AGEB) in the buoy memory is encoded in the Argos message. Age of the observation at the time of the Argos message transmission is therefore:

  • Age = Rank x Block_Period + AGEB
  • And observation time can therefore be computed as following:

  • Observation time = Acquisition time by the satellite - Age
  • If hourly observations are needed (Block_Period=60), the buoy must be activated so that a new observation is available on the hour. If synoptic observations are requested (Block_Period=180), the buoy must be activated accordingly.

     

    Message format

    In white are the first mandatory two blocks of data, i.e. 56 bits (24+32).
    In yellow is the following block of data used for evaluation

     

     

    Item

    Bits

    Pos

    Min

    Max

    Formula / Comments (n = word value)

    Fixed bits in block (o)
    CHK Checksum

    8

    0

    0

    255

    Checksum = Lower 8 bits of the sum of other bytes Y
    Rank Rank of observation

    4

    8

    0

    15

    Rank = n (see 3) Y
    AGEB Age of observation at the time of next block update

    6

    12

    0

    63

    Age (minutes). This timer starts at 0 when the sensor data is updated in the transmission and in incremented in minutes until the next data update (block). Y
    BP Barometric Pressure

    11

    18

    850.0

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    SST Sea Surface Temp.

    9

    29

    -5.0

    35.88

    SST(C) = 0.08 n - 5 Y
    APT Air Pressure tendency

    9

    38

    -25.5

    25.6

    APT(hPa) = 0.1 n - 25.5 Y
    SubM Submergence Count

    6

    47

    0

    100

    Percent of time submerged = 100 n / 63 Y
    VBat Battery Voltage

    3

    53

    free

    free

    Voltage = n +6 Y
    QI quality Indicator

    2

    56

    0.0

    3

    Quality indicator divides the Standard Deviation of the six lowest barometer readings into the following ranges:
    3 - SD is 0.00 to 0.49
    2 - SD is 0.50 to 0.99
    1 - SD is 1.00 to 1.99
    0 - SD is >= 2.00
    Y
    NS Number of samples

    8

    58

    0.0

    160

    Number of samples that were within 1 hPa of 10 lowest median Y
    AP01 1st of the 10 lowest pressure readings

    11

    66

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP02 2nd of the 10 lowest pressure readings

    11

    77

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP03 3rd of the 10 lowest pressure readings

    11

    88

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP04 4th of the 10 lowest pressure readings

    11

    99

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP05 5th of the 10 lowest pressure readings

    11

    110

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP06 6th of the 10 lowest pressure readings

    11

    121

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP07 7th of the 10 lowest pressure readings

    11

    132

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP08 8th of the 10 lowest pressure readings

    11

    143

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP09 9th of the 10 lowest pressure readings

    11

    154

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    AP10 10th of the 10 lowest pressure readings

    11

    165

    850

    1054.7

    Press(hPa) = 0.1 n + 850 Y
    Chk2 Checksum #2

    8

    176

    0

    255

    Checksum = modulus 256 of the sum of the previous 15 bytes Y


    (o) Where "Fixed bits in blocks" is marked as "Y", it means that when a block is actually coded, the exact number of bits are reserved for the considered sensor or information if available. If there is no such sensor in the buoy, then those bits shall be considered as free and can be used for one or more other variables provided that this does not affect the bits used by the surrounding sensors. These bits can also be coded with all bits set to 1 in case they are completely useless. This permits some flexibility in the format.

    Offsets and resolutions are given here as examples and can be modified. The number of bits for each sensor must be changed only if it is not possible to do otherwise (see remark under (o) above).

    We chose to report the barometric tendency in one single word instead of two (one for the absolute value of pressure tendency, the other for the characteristic). Automatic stations are permitted to do so. On the GTS, the characteristic is coded as 2, 4 or 7, according to the sign of the tendency (positive, zero or negative, respectively). This solution is debatable.