DBCP-M2-TEST Recommended format
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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
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:
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:
And observation time can therefore be computed as following:
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.
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.