Label: spd_3d_bin 1.0 version of 2009.01.07 LE
Purpose: Contains results of computing slanted path delay of
radiowave propagation through the 3D, continuous,
heterogeneous atmosphere. The path delay is defined as
a difference in the propagation time between the emitter
and the receiver through the atmosphere and the propagation
between these two points along the geodetic line in
vacuum. The path delay is computed for a set of stations for
a certain epoch at a regular grid of azimuths and elevations.
The grid is equidistant at azimuths and non-equidistant at
elevation angles. The values of path delays computed on
a grid can be used for computing coefficients of the
interpolating functions that enable us to compute
the path delay in an arbitrary direction.
Example: http://astrogeo.org/spd_data/spd_6h_bin
Type: Binary, little endian.
File in spd_3d_bin format consists of rescords of 7 types.
The type of each reacord is determined by the first
8-characters ling field prefix. The records follow in this order:
LAB_REC -- Defines offsets, sizes and the number of other records
TIM_REC -- Defines the start time, stop time of DEL records
and the time step
STA_REC -- Defines station coordinates
MOD_REC -- Defines the slanted path model type and the model description
MET_REC -- Defines escription of the numerical weather model used
for computation
ELV_REC -- Defines the elevation axis for the 2D grid of
path delays through the neutral atmosphere
AZM_REC -- Defines the azimuth axis for the 2D grid of
path delays through the neutral atmosphere
DEL_REC -- Defines the surface pressure surface temperature
and the 2D grid of path delay through the neutral atmosphere.
The file contains only onre record of the fesit seven tpyes and usually
more than one record of DEL_REC. Each DEL_REC corresponds to one time
epoch. The time epochs follow each other in chronological order with
the same time step, without gaps. The time epoch of a specific DEL_REC
is determined bny its index in the file, time of the first epoch, and
the time step.
Decription of individual records:
LAB__REC
CHARACTER PREF*8 ! prefix: LAB_REC
INTEGER*8 LEN ! length of the LAB_REC record
CHARACTER FMT_LAB*40 ! Format label
INTEGER*8 OFF_TIM ! Offset of the TIM record in bytes wrt the file beginning
INTEGER*8 OFF_STA ! Offset of the STA record in bytes wrt the file beginning
INTEGER*8 OFF_MOD ! Offset of the MOD record in bytes wrt the file beginning
INTEGER*8 OFF_MET ! Offset of the MET record in bytes wrt the file beginning
INTEGER*8 OFF_ELV ! Offset of the ELV record in bytes wrt the file beginning
INTEGER*8 OFF_AZM ! Offset of the AZM record in bytes wrt the file beginning
INTEGER*8 OFF_DEL ! Offset of the first TIM record in bytes wrt the file beginning
INTEGER*8 LEN_TIM ! Length of the TIM record in bytes
INTEGER*8 LEN_STA ! Length of the STA record in bytes
INTEGER*8 LEN_MOD ! Length of the MOD record in bytes
INTEGER*8 LEN_MET ! Length of the MET record in bytes
INTEGER*8 LEN_ELV ! Length of the ELV record in bytes
INTEGER*8 LEN_AZM ! Length of the AZM record in bytes
INTEGER*8 LEN_DEL ! Length of the DEL record in bytes
INTEGER*4 TOT_NUM_DEL ! The number of DEL records
TIM_REC
CHARACTER PREF*8 ! prefix: TIM_REC
INTEGER*8 NREC ! The number of time epochs the file contains
INTEGER*4 MJD_BEG ! Modified Julian date at TAI ! Modified Julian date at TAI for the first epochfor the first epoch
INTEGER*4 MJD_END ! Modified Julian date at TAI for the last epoch
REAL*8 TAI_BEG ! TAI for the first epoch. Units: seconds
REAL*8 TAI_END ! TAI for the last epoch. Untis: seconds
REAL*8 TIM_STEP ! Time step. Units: seconds
STA_REC
CHARACTER PREF*8 ! prefix: STA_REC
CHARACTER NAME*8 ! Station name. NB: the station name does NOT necessarily
! controrms any convention. It may be an arbitrary combination
! of characters. Parser software should NOT assign any meaning
! to this field
REAL*8 COO_CFS(3) ! Station coordinates in the crust-fixed coordinate system.
! Units: meters
REAL*8 PHI_GCN ! Station geocentric latitude. Units: radians
REAL*8 PHI_GDT ! Station geodetic latitude. Units: radians
REAL*8 HEI_ELL ! Station height above the reference ellipsoid. Units: meters
REAL*8 HEI_GEOID ! Station height above the geoid. Units: meters
MOD_REC
CHARACTER PREF*8 ! prefix: MOD_REC
INTEGER*4 N_RFR ! Number of components of the model
CHARACTER SPD_TYPE(3)*8 ! Array of names of the slanted path delay model components.
! Supported values:
! total -- Total path delay through the neutral atmosphere
! hydro -- Path delay through the hydrostatic component of the atmosphere
! non-hydr -- Path delay through the non-hydrostatic component of the atmosphere
! undef -- Undefined, not used
INTEGER*8 N_LINES ! Number of lines with model description
INTEGER*8 LEN_TEXT ! Length of the text with model description in bytes
CHARACTER*1, POINTER :: TEXT(:) ! Text with the model description as a string that contains \n characters
! of length LEN_TEXT + 1 (the last character is \0)
MET_REC
CHARACTER PREF*8 ! Prefix: STA_REC
INTEGER*8 N_LINES ! Number of lines with numerical weather model description
INTEGER*8 LEN_TEXT ! Length of the text with teh numerical model description in bytes
CHARACTER*1, POINTER :: TEXT(:) ! Text with the numerical weather model description as
! a string that contains \n characters of length
! LEN_TEXT + 1 (the last character is \0)
ELV_REC
CHARACTER PREF*8 ! Prefix: ELV_REC
INTEGER*8 N_EL ! The number of elements along the elevation angle axis
REAL*4, POINTER :: ELEV(:) ! Array of elevation angles. Dimension: N_EL,
! Units: radians. Array is sorted in decreasing order.
AZM_REC
CHARACTER PREF*8
INTEGER*8 N_AZ ! The number of elements along the azimuth axis
REAL*4, POINTER :: AZIM(:) ! Array of azimuth angles. Dimension: N_AZ,
! Units: radians. Array is sorted in increasing order.
DEL_REC
CHARACTER PREF*8
REAL*4 SURF_PRES ! Surface pressure. Units: Pascal
REAL*4 SURF_TEMP ! Surface air temperature. Units: Kelvin
REAL*4, POINTER :: DEL(:,:,:) ! 3D array of slanted path delay components.
! The first axis runs over elevation angles.
! Dimension: N_EL defined in ELV_REC
! The second axis runs over azimuth angles
! Dimension: N_AZ defined in AZM_REC
! The third runs over components.
! Dimension: N_RFR defined in MOD_REC
! Units: seconds