Data File Format
Data from the Citation research aircraft is provided in ASCII format that includes a metadata header.
The metadata file header is based on Format Specification for Data Exchange, written by Steven E. Gains and R. Stephen Hipsking. An example file with variable labels added is given below:
24 1001 {NLHEAD FFI}
Poellot, Mike {ONAME}
University of North Dakota {ORG}
Citation II Aircraft {SNAME}
Crystal-FACE Field Project {MNAME}
1 1 {IVOL NVOL}
2002 07 18 2003 03 28 {DATE RDATE}
0.0400 {DX}
Time [seconds]; UT seconds from midnight on day aircraft flight started {XNAME}
6 {NV=number of primary variables}
1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 {VSCAL=primary variable scale factors}
999999.9999 999999.9999 999999.9999 999999.9999 999999.9999 999999.9999 {VMISS=primary variable missing values}
Static Pressure [mb] {VNAME[1]}
Air Temperature from the Rosemount Probe [C] {VNAME[2]}
Attack Angle Differential Pressure [mb] {VNAME[3]}
Sideslip Angle Differential Pressure [mb] {VNAME[4]}
Pitot Pressure from Nose Probe [mb] {VNAME[5]}
Pitot Pressure from Wing Probe [mb] {VNAME[6]}
0 {NSCOML=number of special comment lines}
4 {NNCOML=number of normal comment lines}
Preliminary Data {DTYPE=Preliminary/Final Data}
25 Hz Data {VFREQ=frequence of data}
Time STATIC_PR AIR_T_ROSE ATTACK SIDESLIP Pitot_Nose Pitot_Wing {VUNITS=Short Parameter Names}
s mb C mb mb mb mb {VDECS=Parameter Units}
60082.0000 1017.6173 36.4922 -0.2349 -0.0688 3.8009 1.2318
60082.0400 1017.6173 36.4957 -0.2349 -0.0562 3.8853 1.2044
60082.0800 1017.7436 36.4957 -0.2495 -0.0393 3.8747 1.0405Description
A detailed description of each variable used in the above header file is given below:
NLHEAD: number of lines (integer) composing the file header. NLHEAD is the first recorded value on the first line of an exchange file.
FFI: ASCII file format number. For the UND Citation aircraft data this will always be 1001.
ONAME: a character string specifying the name(s) of the originator(s) of the exchange file, last name first. On one line and not exceeding 132 characters.
ORG: character string specifying the organization or affiliation of the originator of the exchange file. Can include address, phone number, email address, etc. On one line and not exceeding 132 characters.
SNAME: a character string specifying the source of the measurements or model results which compose the primary variables, on one line and not exceeding 132 characters. Can include instrument name, measurement platform, etc.
IVOL: volume number (integer) of the total number of volumes required to store a complete dataset, assuming only one file per volume. To be used in conjunction with NVOL to allow data exchange of large datasets requiring more than one volume of the exchange medium.
NVOL: total number of volumes (integer) required to store the complete dataset, assuming one file per volume. If NVOL>1 then each volume must contain a file header with an incremented value for IVOL, and continue the data records with monotonic independent variable marks.
DATE: UT date at which the data within the exchange file begins. For aircraft data files DATE is the UT date of takeoff. DATE is in the form YYYY MM DD (year, month, day) with each integer value separated by at least one space. For example: 1989 1 16 or 1989 01 16 for 16 January 1989.
RDATE: date of data reduction or revision, in the same form as DATE.
DX(s): interval (real) between values of the s-th independent variable, X(i,s), i=1,NX(s); in the same units as specified in XNAME(s). DX(s) is zero for a non-uniform interval. DX(s) is non-zero for a constant interval. If DX(s) is non-zero then it is required that NX(s) = (X(NX(s),s)-X(1,s)) / DX(s) + 1. For some file formats the value of DX also depends on the unbounded independent variable and is expressed as DX(m,s).
XNAME(s): a character string giving the name and/or description of the s-th independent variable, on one line and not exceeding 132 characters. Include units of measure and order the independent variable names such that, when reading primary variables from the data records, the most rapidly varying independent variable is listed first and the most slowly varying independent variable is listed last. Currently this is Time [Seconds] from midnight on day aircraft flight started for all UND exchange files.
NV: number of primary variables in the exchange file (integer). This number plus one (for the time value) gives the number of parameters in the data file.
VSCAL(n): scale factor by which one multiplies recorded values of the n-th primary variable to convert them to the units specified in VNAME(n). Currently this is 1 for all UND Citation Aircraft recorded values.
VMISS(n): a quantity indicating missing or erroneous data values for the n-th primary variable. VMISS(n) must be larger than any "good" data value, of the n-th primary variable, recorded in the file. The value of VMISS(n) defined in the file header is the same value that appears in the data records for missing/bad values of V(X,n). Currently all UND parameters use a VMISS value of 999999.999.
VNAME(n): a character string giving the name and/or description of the n-th primary variable, on one line and not exceeding 132 characters. Include units of measure the data will have after multiplying by the n-th scale factor, VSCAL(n). The order in which the primary variable names are listed in the file header is the same order in which the primary variables are read from the data records, and the same order in which scale factors and missing values for the primary variables are read from the file header records.
NSCOML: number of special comment lines (integer) within the file header. Special comments are reserved to note special problems or circumstances concerning the data within a specific exchange file so they may easily be found and flagged by those reading the file. If NSCOML=0 then there are no special comment lines.
NNCOML: number of normal comment lines (integer) within the file header, including blank lines and data column headers, etc. Normal comments are those which apply to all of a particular kind of dataset, and can be used to more completely describe the contents of the file. If NNCOML=0 then there are no normal comment lines.
DTYPE: version description of the data. Typically either Preliminary or Final Data.
VFREQ: time frequency of the data.
VDESC: a character string on a single line containing a short description of each variable in the exchange file. No spaces are allowed in each short variable description.
VUNITS: a character string on a single line containing the units of each variable in the exchange file. No spaces are allowed in each unit's description.