FXD (Fast Access Data) Structure

The LSD structure is good as highly readable storage and exchange format, but is less suitable for the evaluation of data. It is therefore converted into the FXD format internally. The FXD format is organized station-by-station and stores all data in an array that can be searched by find().

The FXD structure array has one element for each station: fxd(i) is the structure for the i-th station and contains all data from the i-th station.

Conversion from LSD to FXD is done by MKLSLSD2FXD. Empty FXD structures are supplied by MKLSEMPTYFXD.

FXD structrue array
Field Type Units Description
id string - station identifier string
slat number deg station latitude
slon number deg station longitude
selv number km station elevation above reference sphere
phase string matrix - seismic phase name
.phase(j,:) is the seismic phase for which the j-th datum is valid
event string - ID of event to which data is associated. The FXD structure can handle ony one event at a time. If the LSD structure refers to more than one event, the conversion is terminated with an error!
value numeric array type dependent value is an n-by-4 array in which all data is compiled. It contains a data type label, a pointer to the phase name list and the data itself, which is to be interpreted according to the data type label.
.value(j,1): data type label. The following labels are defined:
     0: no data
     1: arrival time
     2: back azimuth
     3: emergence angle
     4: slowness
.value(j,2): phase name pointer, indexes the .phase field. The data in the j-th line of value is valid for the value(j,2)-th phase listed in the phase field.
.value(j,3): minimum data value
.value(j,4): maximum data value

The data is represented as a numeric interval, i.e. as a smallest possible value and a largest possible value. The physical units depend on the data type:
arrival times: seconds
back azimuths: degrees
emegrence angles: degrees
slowness: seconds per degree
atcnt number counter number of arrival time data for this station
bazcnt number counter number of back azimuth data for this station
emergcnt number counter number of emergence angle data for this station
slocnt number counter number of slowness data for this station

eof.