R/V Atlantis Calliope metadata file Wed 02/Jul/2008 18:07:03 Current time zone: GMT Standard Time ================================================== Air temperature; WXT ( WXT5_Ta) Air Temperature, Degrees C __________________________________________________ Depth (12 kHz) ( Depth12) 12 kHz depth (meters) from sea surface obtained by Knudsen bathymetry system. See Knudsen Bathymetry information for sound spped and transducer depth corrections; normally based on 1500 m/s sound speed & corrected for 5.95 meter (19.5 ft) transducer depth. __________________________________________________ Depth (3.5 kHz) ( Depth35) 3.5 kHz depth (meters) to sea surface obtained from Knudsen bathymetry system. See Knudsen Bathymetry information for sound spped and transducer depth corrections; normally based on 1500 m/s sound speed & corrected for 5.95 meter (19.5 ft) transducer depth. __________________________________________________ GPS Navigation data (GPS) Complete NMEA data output from the primary GPS receiver. The single digit following the position information in the GPS_GGA data string indicates the type of GPS fix as follows: 0=No valid fix; 1=Standard; 2=Differential; 3=P-Code NMEA GPS_GGA data sentence: Header , UTC of position, Latitude, N/S, Longitude, E/W, Quality indicator, Number of satellites in use, Horizontal dilution, Altitude, M (meters), Geoidal seperation, M (meters), Age of differential data (secs), Differential reference station I.D. * checksum. The single digit following the position information (quality indicator) indicates the type of position fix: 0=No valid fix; 1=Standard; 2=Differential; 3=P-Code. NMEA GPS-VTG data sentence: Header, Course, T (degrees true), Course, M (magnetic), Speed, N (knots), Speed, K (km/hr) * checksum. __________________________________________________ GPS course over ground (GPS_COG) Course over ground (true) obtained from NMEA GPS_VTG data sentence. NMEA GPS-VTG data sentence: Header, Course, T (degrees true), Course, M (magnetic), Speed, N (knots), Speed, K (km/hr) * checksum. __________________________________________________ GPS speed over ground (GPS_SOG) Speed over ground (knots) obtained from NMEA GPS_VTG data sentence. NMEA GPS-VTG data sentence: Header, Course, T (degrees true), Course, M (magnetic), Speed, N (knots), Speed, K (km/hr) * checksum. __________________________________________________ GPS type (GPS_TYPE) GPS position type (Std, Diff, P-Code) GPS position type indicator is obtained from the "quality indicator" included as part of the NMEA GPS_GGA data sentence. This value applies to the present primary GPS fix only and it is not necessarily an indication of the type of GPS receiver in use. See notes associated with the GPS data item. __________________________________________________ Gill Acoustic Wind Sensor ( Wnd_Gill) Gill WindObserver II Ultrasonic Anemometer Format: id,U axis,V axis,units,sos,temp,status,cs stx = \002, etx = \003, cs = check sum (these items may be deleted) id = sensor identification U & V axis wind speed (meters/sec) units = M (meters) sos = speed of sound (m/sec) temp = air temperature (C) status: 0 = OK & 60= heater enabled & OK (any other value indicates a possible problem) Setup: *id enters setup mode, Q exits setup mode, ? initiates polled mode D1 => serial #, D3 => setup information id => data in polled mode ( not required) Nx id = "x" Mn Operating mode Gnnnn Averaging period An SOS & Temp output Un Units Hn Heater enable Xn Axis alignment BnFnEn Com protocol Calliope default: NX M3 G0015 A3 U1 H2 X1 B3 F1 E1 id=X, polled UV mode, 15 sec average, meters/sec sos & temp output, heater active, U axis alignment 9600,N,8,1,full duplex __________________________________________________ Gyro heading (Gyro) Format: Heading(degrees true) Ship's heading (degrees true) obtained from the HEHDT primary sensor. __________________________________________________ Hull temperature - Raw ( SBE48_raw) __________________________________________________ IMET Air Temperature (Air_Temp) Format: Temp (C) Data is obtained from IMET_HRH primary sensor. __________________________________________________ IMET Barometric Pressure (IMET_BPR) Format: Barometric pressure (milli-bars) Sensor installation dates: March 5, 2003 (Jacksonville, Fla.) __________________________________________________ IMET Humidity (IMET_HRH) Format: Humidity (%RH), Temperature (C) Note - IMET air temperature (Air_Temp) is obtained from this instrument. Sensor installation dates: March 5, 2003 (Jacksonville, Fla.) __________________________________________________ IMET Precipation (IMET_PRC) IMET_PRC Precipitation (millimeters) __________________________________________________ IMET Shortwave Radiation (IMET_SWR) Format: Radiation (watts/square meter) __________________________________________________ IMET Wind (IMET_WND) Format: X, Y, Total, Max, Min, LastVane, LastCompass, C1, C2 Wind X (m/sec), Positive for a stbd to port wind Wind Y (m/sec), Positive for a bow to stern wind Wind Total (m/sec), Averaged over previous minute Wind Max (m/sec, 15 sec interval), Wind Min (m/sec, 15 sec interval), Last Vane Reading (deg), Last Compass Reading (deg), Counter1 ("0"), Counter2 ("4") Note - Wind direction is no longer provided as a single quantity. Direction values are ship relative. The wind sensor does not have a compass installed. (LastCompass should always be 0.0). Sensor installation dates: March 5, 2003 __________________________________________________ IMET relative humidity (HRH) Format: Humidity (%RH) Data is obtained from IMET_HRH primary sensor. __________________________________________________ Knudsen bathymetry ( Knudsen) Depth to surface (meters). Format: $PKEL99,HF,xx.xx,cc.cc,LF,yy.yy,cc.cc,ssss,lat,lon "HF" High freq header xx.xx 12 kHz depth to surface using cc.cc & ssss corrections (meters) cc.cc depth of 12 kHz transducer (meters) "LF" Low freq header yy.yy 3.5 kHz depth to surface using cc.cc & ssss corrections (meters) cc.cc depth of 3.5 kHz transducer (meters) ssss sound speed used for depth calculations (m/s) Lat Latitude Lon Longitude Note - 12 kHz and 3.5 kHz transducers are at same depth on Atlantis. __________________________________________________ Latitude (GPS_Lat) GPS_LAT GPS Latitude __________________________________________________ Longitude (GPS_Lon) GPS_LON GPS Longitude __________________________________________________ NMEA Gyro (HEHDT) Ship's heading obtained from the Sperry Gyro. NMEA format: Header ($HEHDT), Heading (degrees), T (true), Heading (degrees), M (magnetic) * checksum. Version 2.20 (1/1/97) of the NMEA 0183 standard does not show magnetic heading in this data sentence and the validity of this item is questionable. __________________________________________________ NorthStar941 GPBWR ( GPBWR_5006) NorthStar 941 receiver's Bearing & Distance to Waypoint NMEA sentence. This data is normally only used to provide a real time waypoint data display. Format: $--BWR,hhmmss.ss,lat,a,lon,a,x.x,T,x.x,M,x.x,N,c--c*hh time = UTC of observation Lat & Lon of waypoint x.x,T = true bearing to waypoint x.x,M = magnetic bearing to waypoint x.x,N = nautical miles to waypoint c--c = waypoint ID *hh = checksum __________________________________________________ NorthStar941 GPRMC ( GPRMC_5006) NorthStar 941 GPS receiver NMEA output Format: $--RMC,hhmmss.ss,S,lat,a,lon,a,x.x,y.y,ddmmyy,m.m,d*hh Time = UTC of position fix S = Status ("A" = valid, "V" = receiver warning) Lat & Lon x.x = speed over ground (knots) y.y = Course over ground (degrees true) ddmmyy = date m.m,d = magnetic variation, degrees ("E" subtracts from true, "W" adds to true) __________________________________________________ NorthStar941 GPZTG ( GPZTG_5006) NorthStar941 GPS receiver UTC & Time to Waypoint NMEA output. This data is normally used to provide real time waypoint data display. Format: $--ZTG,hhmmss.ss,hhmmss.ss,c--c*hh UTC time of observation Time-to-go to waypoint c--c = Waypoint ID *hh = checksum __________________________________________________ Phins attitude raw ( PHTRH) Format: $PHTRH,x.xx,a,y.yy,b,z.zz,c*hh x.xx = pitch (degrees) a = "M" for bow up, "P" for bow down y.yy = roll (degrees) b = "B" for port down, "T" for port up z.zz = heave (meters) c = "U" for Phins going Up, "O" for going down hh = checksum Atlantis Phins data is broadcast on 55005 at 1 Hz __________________________________________________ Phins heading ( PhinsHd) __________________________________________________ Phins heading raw ( HEHDT_005) Format: $HEHDT,x.xxx,T*hh x.xxx = true heading (degrees) hh = checksum Atlantis Phins data is broadcast on 55005 at 1Hz __________________________________________________ Position from GPS receiver (Lat_Lon) Format: decimal Latitude, N/S, decimal Longitude, E/W __________________________________________________ Rain Intensity; mm/hr ( WXT5_Ri) Data Format: This value is calculated over 10 second intervals. __________________________________________________ Relative Wind Speed; WXT ( WXT5_Sm) Ship relative wind speed (m/s) Data Format xx.x Wind sampling done at 2 Hz and averaged over 10 seconds - new data is available at 10 second intervals. __________________________________________________ SBE45 conductivity ( SBE45C) Format cc.cccc (mmho/cm) SBE45 Conductivity (mmho/cm) Saltwater supplied by ship's system (bow intake). __________________________________________________ SBE45 salinity ( SBE45S) SBE45 Salinity PSU Seawater supplied by ship's system (midship sea chest intake). __________________________________________________ SBE45 sound velocity ( SBE45V) SBE45 surface sound velocity (m/sec) Seawater supplied by ship system (midship sea chest intake). __________________________________________________ SBE45 temperature ( SBE45T) SBE45 temperature (degrees C) Seawater supplied by ship system (midship sea chest intake). __________________________________________________ SBE45 thermosalinograph ( SBE45) SBE45 thermosalinograph (serial# 0122) Installed July 4, 2005 Seawater supplied by ship's system (midship sea chest intake). Format: ttt.tttt, cc.ccccc, sss.ssss, vvvv.vvv t = temperature (degrees C) c = conductivity (S/m) s = salinity (psu) v = sound velocity (m/sec) __________________________________________________ Salinity (Salinity) Format: ss.ssss Salinity calculated from SSTMP and SSCND data values in accordance with UNESCO 44. __________________________________________________ Sea Surface Conductivity (SSCND) Format: Sea surface conductivity (mmho/cm) Sensor installation dates: July 01, 2005 (Seattle Wa.) Cal 6/05 __________________________________________________ Sea Surface Temperature (SSTMP) Format: Sea surface temperature (C) Falmouth Scientific Sensor installation dates: Aug 01, 2005 (Seattle, Wa) Cal 6/05 __________________________________________________ Sound velocity (SSV) Sea surface sound velocity (meters/second) calculated from SSTMP and SSCND data values. Intermediate salinity calculations are made in accordance with UNESCO 44. __________________________________________________ True wind direction (Wnd_Dir) Wind: * * * 01/31/96 Revision: * * * Wind Y (m/sec), Wind X (m/sec), Wind Total (m/sec), Wind Max (m/sec, 15 sec interval), Wind Min (m/sec, 15 sec interval), Last Vane Reading (deg), Last Compass Reading (deg), Counter1 ("0"), Counter2 ("4") Note - Wind direction is no longer provided as a single quantity. Direction values are ship relative. The wind sensor does not have a compass installed. (value should always be 0.0). WHOI ship installation convention: "Wind Y" is positive for a stbd to port wind. "Wind X" is positive for a bow to stern wind. __________________________________________________ True wind direction; WXT ( TWD_5) Degrees Values are calculated from the Vaisala WXT510 Weather Transmitter raw data corrected for sensor alignment error and combined with the ship's gyro heading and GPS SOG and COG values. __________________________________________________ True wind speed (Wnd_Spd) Wind: * * * 01/31/96 Revision: * * * Wind Y (m/sec), Wind X (m/sec), Wind Total (m/sec), Wind Max (m/sec, 15 sec interval), Wind Min (m/sec, 15 sec interval), Last Vane Reading (deg), Last Compass Reading (deg), Counter1 ("0"), Counter2 ("4") Note - Wind direction is no longer provided as a single quantity. Direction values are ship relative. The wind sensor does not have a compass installed. (value should always be 0.0). WHOI ship installation convention: "Wind Y" is positive for a stbd to port wind. "Wind X" is positive for a bow to stern wind. __________________________________________________ True wind speed & direction (TWind) __________________________________________________ True wind speed ( TWS_5) m/s Data format xx.x Values are calculated from the Vaisala WXT510 Weather Transmitter raw data corrected for sensor alignment error and combined with the ship's gyro heading and GPS SOG and COG values. __________________________________________________ WetLabs fluorometer ( WStar) Chlorophyll - Ex: 460 nm, Em: 695 nm, Sensitivity: >=0.03 mg/l Dynamic range: 0.03-75 mg/l Output 0-5 volts WS3S-582P (July 4, 2005) WET Labs WETStar fluorometer installed in the ROV Hanger using ship's saltwater supply. __________________________________________________ WETLabs Sea Surface Fluorometer ( WStar2) Chlorophyll - Ex: 460 nm, Em: 695 nm, Sensitivity: >=0.03 mg/l Dynamic range: 0.03-75 mg/l Output 0-5 volts WS3S-901P (January 2005) WETLabs WETStar fluorometer installed in the Hydrolab using clean seawater supply. __________________________________________________ WXT510 #5 ( WXT5) WXT5 Vaisala WXT510 Weather Transmitter Data Format: WXT5 39240.67178 16:07:22 5R0,Dm=048D,Sn=0.0M,Sm=0.1M, Sx=0.2M,Ta=24.5C,Ua=35.7P,Pa=1018.2H,Rc=0.00M,Ri=0.0M WXT5 39240.67178 16:07:22 = Calliope designator and time values (time stamps are GMT) 5R0 = Instrument's polled data request cmd ("5" is inst address) Dm = Wind direction, deg (2 Hz samples, 10 sec average) 0 deg wind comes over the bow Sn = Wind speed min, m/sec (2 Hz, 10 sec sample period) Sm = Wind speed average, m/sec (2 Hz, 10 sec sample period) Sx = Wind speed max, m/sec (2 Hz, 10 sec sample period) Ta = Air temperature, degrees C Ua = Relative humidity, % Pa = Barometric pressure, hPa Rc = Rain accumulation, mm (accumulation is updated in 10 sec intervals) The accumulation value is reset only when the sensor power is reset. Ri = Rain intensity, mm/hour Wind speed and direction are given in meteorological terms: a "0" degree wind comes from the bow; a "90" degree wind comes from the Stbd side. Wind speed and direction values are ship relative and direction has not been corrected for mounting alignment error. Wind sampling is done at 2 Hz and averaged over 10 seconds - new data is available at 10 sec intervals. *** this is a new sensor; installed 10/17/07 true wind calculations have not been configured yet. __________________________________________________ __________________________________________________ Defined constants: User = Calliope Password = datalogger MailBox = InBox IncomingMailServer = 199.92.161.2 OutgoingMailserver = 199.92.161.2 MailPort = 25 from_Address = Calliope@atlantis.whoi.edu to_Address = bwalden@whoi.edu ErrorRptAddress = cerror@sssg1.whoi.edu,sssg@atlantis.whoi.edu CruiseID = NA IMETSensorOffset = 0.0 WXT510SensorOffset = 0.0 __________________________________________________ __________________________________________________ Auxiliary information: Calliope Data Files April 20, 2008 General considerations - The Calliope system does not normally log all the data available or all the data it obtains and uses internally; it logs a subset on a timed basis individually specified for each data item. Data is frequently obtained and used for calculations without being logged due to a difference between the data collection interval and the log cycle. If the log file recording rate was not the same as the data collection rate, post-processing calculations may not give the same answers as the originals even though all calculations are done correctly. This is because the original calculations would have new data available at the collection rate whereas post-processing would only have the logged data subset. The true wind calculation provides a good example; determining true wind speed and direction requires the wind sensor data plus heading from a compass or gyro and COG and SOG from a GPS. Normally heading data is obtained at a rapid rate compared to wind data but they are both recorded at about the same interval. This means that when the Calliope code makes the true wind calculation it is likely to use newly obtained heading data, which may not be logged. Clearly, attempting to check the Calliope calculations using the logged data will be difficult but, if the logging rates have been chosen reasonably, post-processing will provide valid, useful results. Log Files - The Calliope system generates data files of two types: 1) asynchronous, single-item-per-line, time stamped ASCII and 2) synchronous, multi-item-per-line, comma delimited (CSV). A single file of the first type is always created containing data items logged at the time interval specified by the Calliope configuration. Each line starts with a data identifier followed by the date and time given in the form used by Visual Basic (number of days since Dec. 31, 1899; the 31st is day #1) and then the time in normal human readable form. These values are followed by the data terminated with a . Log files are normally created at midnight GMT and the name of the file provides ship and creation date information with a “.dat” extension. The date value within the file name is always based on GMT. The first line of the file provides ship, date and initialization local time information. The second line indicates the local time zone and the third provides a reminder that Calliope data timestamps are always GMT. This is followed by a line containing “****” indicating the start of recorded data. The Calliope data collection application always uses GMT timestamp values regardless of the time zone setting of the application computer. However, the start time for new data files is controlled by an entry in the configuration file. Regardless of when a file is started, the date information used to construct the file name is based on GMT. Note however that any date and time information included in the data file headers is local time. If date or time values are included in data files as logged values, these will also be local values (with GMT timestamps). Time values are handled in this manner to allow more convenient use of local time for controlling Calliope’s activities if desired. As an example, starting new files at a particular local time can be preferable to midnight GMT when instrumentation deployment activities are scheduled on a daily basis. Note that GMT will be used exclusively if the computer’s time is set to GMT. All lines after the header’s “****” contain data as shown in the following example taken from an Oceanus file named “OC020915.dat”. For this example, most items are being logged at 1-minute intervals; HEHDT, PKEL99, Salinity, and SSV are exceptions. The header indicates that the Calliope computer was set to Azores Standard Time, which is one hour behind GMT. The file was started at approximately midnight local time and the timestamps reflect the 1 hour difference between local and GMT. R/V Oceanus Calliope data file, Sun 15/Sep/2002 00:00:11 Current time zone: Azores Standard Time (GMT-1) Data timestamps are GMT **** IMET_WND 37514.00031 01:00:26 1.14 –2.55 2.8 3.3 2.4 161.2 0 4 IMET_HRH 37514.00031 01:00:26 99.253 19.819 IMET_SWR 37514.00031 01:00:26 0.1 IMET_BPR 37514.00031 01:00:26 1021.66 IMET_PRC 37514.00032 01:00:27 -0.00 0.00 7.69 SSTMP 37514.00032 01:00:27 +24.6322 SSCND 37514.00032 01:00:27 +50.0594 HEHDT 37514.00032 01:00:27 $HEHDT,025.7,T PKEL99 37514.00034 01:00:29 $PKEL99,15.01,00.00,1500 Salinity 37514.04216 01:00:42 33.0489 SSV 37514.04216 01:00:42 1531.3961 TWind 37514.04216 01:00:43 2.7932 181.6 GPS 37514.04217 01:00:44 $GPGGA,010043.043,4131.4319,N, 07040.3348,W,3,08,1.0,026.0,M,034.4,M,,*75,$GPGXP,010043,4131.4319,N,07 040.3348,W*5D,$GPGLL,4131.4319,N,07040.3348,W,010043.043,A*21,$GPVTG,34 1.5,T,357.1,M,000.0,N,000.0,K*4D HEHDT 37514.04228 01:00:58 $HEHDT,025.7,T IMET_WND 37514.04249 01:01:11 1.14 -2.55 2.8 3.3 2.4 161.2 0.0 0 4 IMET_HRH 37514.04266 01:01:26 99.253 19.818 IMET_SWR 37514.04266 01:01:26 0.1 IMET_BPR 37514.04267 01:01:26 1021.71 IMET_PRC 37514.04267 01:01:27 0.00 0.00 7.69 SSTMP 37514.04268 01:01:27 +24.6304 SSCND 37514.04268 01:01:28 +50.0560 HEHDT 37514.04268 01:01:28 $HEHDT,025.6,T TWind 37514.04286 01:01:43 2.8356 183.7 GPS 37514.04286 01:01:43 $GPGGA,010142.043,4131.4306,N, 07040.3343,W,3,08,1.0,028.3,M,034.4,M,,*7D,$GPGXP,010142,4131.4306,N,07 040.3343,W*58,$GPGLL,4131.4306,N,07040.3343,W,010142.043,A*24,$GPVTG,34 1.5,T,357.1,M,000.0,N,000.0,K*4D HEHDT 37514.04306 01:01:58 $HEHDT,025.7,T IMET_WND 37514.04318 01:02:11 1.06 -2.63 2.8 3.5 2.4 165.3 0.0 0 4 IMET_HRH 37514.04336 01:02:26 99.253 19.804 IMET_SWR 37514.04336 01:02:26 0.0 IMET_BPR 37514.04336 01:02:26 1021.70 IMET_PRC 37514.04336 01:02:26 0.00 0.00 7.70 SSTMP 37514.04337 01:02:27 +24.6314 SSCND 37514.04337 01:02:27 +50.0593 HEHDT 37514.04337 01:02:27 $HEHDT,025.7,T PKEL99 37514.04339 01:02:29 $PKEL99,15.02,00.00,1500 Salinity 37514.04354 01:02:42 33.0511 SSV 37514.04354 01:02:42 1531.3987 TWind 37514.04354 01:02:42 2.5863 181.0 Note that the GPS data in the above example contains line-formatting characters that are not normally present in the real data files. The GPS data item above was defined as four NMEA sentences and the Calliope program concatenates multi-line data, replacing line termination characters with commas. characters are only present at the end of each data item. The “CSV” format file uses the same naming convention except that an underscore and two-digit number follow the date/time. The extension is always “csv”. CSV files are normally started at midnight GMT but the start time can be delayed by an amount specified in the configuration file. CSV files begin with a header line that identifies the ship and a line that identifies the data items in each of the following comma delimited columns. The last item in this second line is always the header line’s checksum. The content of these files can be changed by a number of methods and if this is done, a new file is created having a new file name; the two-digit number following the underscore is incremented. The header line identifying the file’s data items is also corrected. The rate at which data is added to a CSV file is normally once per minute but this can be changed by an entry in the Calliope configuration file. Each line begins with a date and GMT time stamp and contains the most recent data available at the time of the entry. Data is not repeated; if new data is not available when a line is to be added, the corresponding column is left blank. The final item in each line is the checksum of the data identifier header line - not the data line’s checksum. This is included so that when data lines of this type are broadcast to other applications, it is possible for these applications to determine if the correct header is being used. The following is an example taken from the file “OC020915_00.csv”. R/V Oceanus Calliope CSV data file (timestamps are GMT) Date, Time, SSTMP, SSCND, Gyro, Salinity, Wnd_Spd, Wnd_Dir, Depth, HdChkSum=OF 2002/09/15, 00:00:25, +24.630, +50.058, 025.7, 33.049, 2.67, 185.4, 115.01, 0F 2002/09/15, 00:01:25, +24.631, +50.060, 025.6, 33.050, 2.79, 181.5, 115.02, 0F 2002/09/15, 00:02:25, +24.631, +50.059, 025.7, 33.050, 2.83, 183.7, 115.01, 0F 2002/09/15, 00:03:25, +24.633, +50.057, 025.7, 33.047, 2.58, 181.0, 115.03, 0F 2002/09/15, 00:04:25, +24.633, +50.060, 025.7, 33.049, 2.43, 181.8, 115.06, 0F 2002/09/15, 00:05:25, +24.633, +50.057, 025.6, 33.046, 2.66, 178.1, 115.01, 0F 2002/09/15, 00:06:25, +24.633, +50.057, 025.7, 33.047, 2.49, 179.5, 115.01, 0F 2002/09/15, 00:07:25, +24.632, +50.060, 025.6, 33.050, 2.71, 181.5, 115.01, 0F 2002/09/15, 00:08:25, +24.632, +50.061, 025.7, 33.051, 3.02, 179.2, 115.03, 0F 2002/09/15, 00:09:25, +24.632, +50.058, 025.7, 33.048, 2.76, 180.6, 115.04, 0F 2002/09/15, 00:10:25, +24.630, +50.058, 025.7, 33.049, 3.03, 178.9, 115.03, 0F 2002/09/15, 00:11:25, +24.632, +50.058, 025.7, 33.048, 3.47, 178.2, 115.02, 0F Special Files - A Calliope file entry transaction definition can define special files having a specified name and data content. The data format will be as described above for the asynchronous .dat file. Files of this type are generally used to record a limited amount of data, possibly triggered by an “event” of some nature. Raw Data Files - The Calliope data input code can be configured to time stamp (GMT) and log all data received on a particular port. The same file name can be specified for more than one port allowing a single raw data file to hold a number of different data items. Raw data file names are specified when the files are activated; Calliope appends the yymmdd date and will always use a ".dat" extension (i.e. Pitch_080415.dat). Metadata The Calliope system generates a metadata file (Metadata.txt). This is a simple text file containing information on the various data sources listed by sensor name and the designator used in the header information of the primary data file types. The file also lists the constants defined by files in the Constants directory (i.e. calibration constants) and includes a copy of the file Metadata2.txt (located in the Calliope/Metadata directory), which can contain addition information entered by the application user. Hopefully, the resulting Metadata file contains enough information to make effective use of the data contained in the other files (i.e. format, units, sensor type, calibration dates, etc.). In addition, there may be a second metadata file in the primary data directory named MetaDataAux.txt. This file is intended to provide a location for initialization and other functions to store useful but non-data information obtained from sensor interrogations (such as the calibration date of an IMET sensor). Timestamp formats The Calliope data collection application always uses GMT timestamp values regardless of the time zone setting of the application computer. Also, the date used to generate the name of a data file is based on GMT. However, new files are not necessarily started at midnight GMT (file start times are controlled by an entry in the Calliope configuration file) and any date and time information included in data file headers is local time. If date or time values are included as logged values in data files, these will also be local values. The Calliope ".dat" data file headers indicate the local time zone setting when the file was started. Individual items in Calliope ".dat" data files are time stamped with two different formats. The first timestamp value is in the format used by Microsoft Visual Basic: the number of days since December 31, 1899 (Dec. 31 is day 1, not day 0). Its primary purpose is to provide a continuously increasing date and time indicator for use in data graphing applications. The VB format facilitates this for some applications but converting the number to the normal human readable form can be painful. The second timestamp value (hh:mm:ss format) in combination with the date in the file header may eliminate the need for this conversion. If not, the following may be helpful: 00.00 is 00:00:00 on Dec. 30, 1899. 00.50 is 12:00:00 (noon) on the same day. 35390.58333 is 14:00:00 May 15, 1998.