#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ # $Id: FormatNotes,v 1.13 2007/05/07 22:48:58 swift Exp $ #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ # RCS Log: # # $Log: FormatNotes,v $ # Revision 1.13 2007/05/07 22:48:58 swift # Made corrections in FormatNotes with respect to temperature encoding. # # Revision 1.12 2006/11/24 19:38:15 swift # Corrected format notes for high-res CTD data to account for changes in # Sbe41cp firmware revisions. # # Revision 1.11 2006/10/13 18:40:13 swift # Modifications to account for changes in the formatting of CTD data. # # Revision 1.10 2006/01/31 22:38:03 swift # Eliminated "dbars" and "C" from ParkPt entries. # # Revision 1.9 2006/01/28 19:24:16 swift # Integrated the SBE43i oxygen sensor into iridium firmware. # # Revision 1.8 2005/10/24 22:45:24 swift # Change message extension from 'prf' to 'msg'. # # Revision 1.7 2005/09/05 16:04:16 swift # Fleshed out formatting documentation for iridium messages. # # Revision 1.6 2005/03/30 21:11:09 swift # Description of the encoding of data. # # Revision 1.5 2004/12/29 23:12:17 swift # Deleted format notes that pertained only to ARGOS firmware. # # Revision 1.4 2004/04/10 18:38:27 swift # Format description for use with 28-bit Argos ids. # # Revision 1.3 2004/04/10 18:36:54 swift # Format description for use with 20-bit Argos ids. # # Revision 1.2 2003/11/21 02:46:23 swift # Added documentation for the SBE41 status buts. # # Revision 1.1 2003/11/12 23:05:54 swift # Initial revision # #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Format specification for APF9i firmware revision. ================================================= Iridium message files end with a ".msg" extension. Each iridium message file consists of blocks of similar data presented in the order that they were collected during the profile cycle. This firmware revision includes five blocks of data: 1) Park-phase PT samples: These are hourly low-power PT samples collected during the park phase of the profile cycle. 2) Low resolution PTSO samples: The deep parts of the profile can be represented using low-resolution spot samples collected at predetermined pressures. Low resolution spot sampling in the deep water was implemented as an energy savings measure. 3) High resolution PTSO samples: The shallower parts of the profile can be represented with high resolution (ie., 2 decibar) bin-averaged PTSO samples. In continuous profiling mode, the CTD samples at 0.83Hz and stores the data for later binning and averaging. 4) GPS fixes: After the profile is executed and the float reaches the surface, the location of the profile is determined via GPS. 5) Biographical & engineering data: Various kinds of biographical and engineering data are collected at various times during the profile cycle. Usually, only one telemetry cycle is required to upload the data to the remote host computer. However, sometimes the iridium connection is broken or the quality of the connection is so poor that the float will abort the telemetry attempt, wait a few minutes, and then try again. Data blocks 4 and 5 will be repeated for each telemetry cycle of a given profile. A description of the format for each of these blocks of data follows. 1) Park-phase PT sample format. ------------------------------- Hourly low-power PT samples are collected during the park phase of the profile cycle. The park phase is also when active ballasting is done. Each sample includes the date & time of the sample, the unix epoch (ie., the number of seconds since 00:00:00 on Jan 1, 1970), the mission time (ie., the number of seconds since the start of the current profile cycle), the pressure (decibars), and the temperature (C). For example: |------- date -----| UnixEpoch MTime P T ParkPt: Aug 27 2005 13:28:01 1125149281 21615 999.8 4.1024 ParkPt: Aug 27 2005 14:27:57 1125152877 25212 1006.8 4.1554 ParkPt: Aug 27 2005 15:27:57 1125156477 28812 1004.6 4.1710 ParkPt: Aug 27 2005 16:27:57 1125160077 32412 1004.0 4.1775 ParkPt: Aug 27 2005 17:27:57 1125163677 36012 1000.2 4.1525 ParkPt: Aug 27 2005 18:27:57 1125167277 39612 1001.0 4.1381 ParkPt: Aug 27 2005 19:27:57 1125170877 43212 998.6 4.1030 2) Low resolution PTSO sample format. ------------------------------------- The SBE41CP that is used on iridium floats has features that enable subsampling of the water column (similar to the SBE41) as well as the ability to bin-average a continuous sampling of the water column. For subsampled data, the values of pressure, temperature, and salinity are not encoded but are given in conventional units (decibars, C, PSU). This firmware was designed for iridium floats with an SBE43 (a.k.a. IDO) oxygen sensor. The IDO sensor does not report the actual oxygen concentration. Instead, it reports the "oxygen frequency" (Hertz) that requires additional processing to obtain oxygen concentration via calibration equations. The calibration equations are expressed in terms of calibration coefficients that are specific to individual IDO sensors. For example: $ Discrete samples: 22 $ p t s ofreq 1000.99 3.8633 34.4704 4073 (Park Sample) 1998.44 2.1449 34.6194 4699 1949.02 2.2140 34.6145 4685 1899.05 2.2602 34.6102 4661 1849.34 2.3056 34.6082 4638 1799.28 2.3576 34.6041 4616 1748.29 2.4284 34.5999 4604 1698.73 2.4919 34.5946 4573 3) High resolution PTSO sample format. -------------------------------------- For continuously sampled data, 2-decibar bins are used for bin-averaging. These data are encoded as three 16-bit integers (PTS), a 16-bit oxygen frequency, and then an 8-bit integer that represents the number of samples in the bin: # Nov 11 2006 08:17:34 Sbe41cpSerNo[1140] NSample[4192] NBin[488] 000000000000000000[2] 002964D8899629A70C 003C64DA899629A30C 005064DA899629A20C 006464DD899629A10A 007864DE8996299C0B 008C64E18996299A0B 00A064E28996299A0A 00B464E5899629980B 00C964E3899629940A 00DD64E2899629930A 00F064E48996299009 010564E48996298C0A 011864E68996298A09 012C64E6899629880B [snippage...] 25F80FA486A30FD80E 260C0FA286A30FDA0F The first 4-bytes of the encoded sample represents the pressure in centibars. The second 4-bytes represents the temperature in millidegrees. The third 4-bytes represent the salinity in parts per million. The next 4-bytes represent the oxygen frequency in Hertz. The final 2-bytes represent the number of samples collected in the 2dbar pressure bin. For example, the encoding: 260C0FA286A30FDA0F represents a bin with (0x0F=) 15 samples where the mean pressure was (0x260C=) 974.0dbars, the mean temperature was (0x0FA2=) 4.002C, the mean salinity was (0x86A3=) 34.467PSU, and the mean oxygen frequency was (0x0FDA=) 4058Hz. The PTSO values were encoded as 16-bit hex integers according to the functions below. Integers in square brackets '[]' indicate replicates of the same encoded line. For example, a line that looks like: 000000000000000000[2] indicates that there were 2 adjacent lines with the same encoding....all zeros in this case. /*------------------------------------------------------------------------*/ /* function to encode the number of samples as an 8-bit unsigned integer */ /*------------------------------------------------------------------------*/ /** This function encodes the number samples in the bin average as an 8-bit unsigned integer with protection against overflow. The encoding accounts for the full range of 16-bit unsigned integers but only values in the open range: 0=255) ? 0xff : NSample; return N; } /*------------------------------------------------------------------------*/ /* function to encode oxygen as a 2-byte unsigned integer */ /*------------------------------------------------------------------------*/ /** This function implements the hex-encoding of IEEE-formattted floating point oxygen data into 16-bit unsigned integers with 2's-complement representation. The encoding formula accounts for the full range of 32-bit IEEE floating point values but only values in the open range: -4095=3); if (finite(o2)) { /* assign out-of-range values to sentinel values */ if (o2>=61439) O2=0xefff; else if (o2<=-4095) O2=0xf001; /* encode the oxygen frequency (rounded) */ else O2 = (unsigned int)(o2 + ((o2<0) ? -0.5 : 0.5)); /* express in 16-bit 2's-complement form */ if (O2<0) O2+=0x10000L; } return O2; } /*------------------------------------------------------------------------*/ /* function to encode pressure as a 2-byte unsigned integer */ /*------------------------------------------------------------------------*/ /** This function implements the hex-encoding of IEEE-formattted floating point pressure data into 2-byte signed integers with 2's complement representation. The encoding formula accounts for the full range of 32-bit IEEE floating point values but only values in the open range: -3276.7=3); if (finite(p)) { /* assign out-of-range values to sentinel values */ if (p>=3276.7) P=0x7fffL; else if (p<=-3276.7) P=0x8001L; /* encode the pressure as the number of centibars (rounded) */ else P = (long int)(10*(p + ((p<0) ? -0.05 : 0.05))); /* express in 16-bit 2's-complement form */ if (P<0) P+=0x10000L; } return P; } /*------------------------------------------------------------------------*/ /* function to encode salinity as a 2-byte unsigned long integer */ /*------------------------------------------------------------------------*/ /** This function implements the hex-encoding of IEEE-formattted floating point salinity data into 16-bit unsigned integers with 2's complement representation. The encoding formula accounts for the full range of 32-bit IEEE floating point values but only values in the open range: -4.095=3); if (finite(s)) { /* assign out-of-range values to sentinel values */ if (s>=61.439) S=0xefffL; else if (s<=-4.095) S=0xf001L; /* encode the salinity as the number of parts-per-ten-million (rounded) */ else S = (long int)(1000*(s + ((s<0) ? -0.0005 : 0.0005))); /* express in 16-bit 2's-complement form */ if (S<0) S+=0x10000L; } return S; } /*------------------------------------------------------------------------*/ /* function to encode temperature as a 2-byte unsigned integer */ /*------------------------------------------------------------------------*/ /** This function implements the hex-encoding of IEEE-formattted floating point temperature data into 16-bit unsigned integers with 2's complement representation. The encoding formula accounts for the full range of 32-bit IEEE floating point values but only values in the open range: -4.095=3); if (finite(t)) { /* assign out-of-range values to sentinel values */ if (t>=61.439) T=0xefffL; else if (t<=-4.095) T=0xf001L; /* encode the temperature as the number of tenths of millidegrees (rounded) */ else T = (long int)(1000*(t + ((t<0) ? -0.0005 : 0.0005))); /* express in 16-bit 2's-complement form */ if (T<0) T+=0x10000L; } return T; } 4) GPS fix format. ------------------ Each telemetry cycle begins with the float attempting to acquire a GPS fix. The fix includes the amount of time required to acquire the fix, the longitude and latitude (degrees), the date & time of the fix, and the number of satellites used to determine the fix. For example: # GPS fix obtained in 98 seconds. # lon lat mm/dd/yyyy hhmmss nsat Fix: -152.945 22.544 09/01/2005 104710 8 Positive values of longitude, latitude represent east, north hemispheres, respectively. Negative values of longitude, latitude represent west, south hemispheres, respectively. The date is given in month-day-year format and the time is given in hours-minutes-seconds format. If not fix was acquired then the following note is entered into the iridium message: # Attempt to get GPS fix failed after 600 seconds. 5) Biographical & engineering data. ----------------------------------- These data have the format, "key"="value", as shown in the following examples: ActiveBallastAdjustments=5 AirBladderPressure=119 AirPumpAmps=91 AirPumpVolts=192 BuoyancyPumpOnTime=1539 Interpretation of these data requires detailed knowledge of firmware implementations.