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