flac - creates EDIS 1B LAC or GAC format files from raw HRPT pass data

flac - Creates EDIS 1B LAC or GAC format files from raw HRPT pass data

SYNOPSIS

flac  [ parameter=value ... ]  [ output file ]
flac  [ parameter=value ... ]  [ directory   ]
flac  [ parameter=value ... ]  [ tape device ]

Parameters are: on_pass_disk, pass_number, input_file, files_per_pass, pass_year, use_master, master_file, start_time, num_lines, channels, packed_fmt, orbit_number, hrpt_format.

DESCRIPTION

flac creates Environmental Data Information Service (EDIS) Local Area Coverage (1B LAC) files from raw AVHRR pass data. LAC output files containing up to 5 channels are supported; 5 channel packed LAC format is supported, and is the most popular choice.

flac can also produce EDIS 1B GAC output, provided that the input data stream is DOMSAT GAC data. See the parameter hrpt_format described below.

The following input/output cases are supported:

One output UNIX file, with user supplied name, when input is from archive tape, raw pass disk, or UNIX file.

One or more output UNIX files, with automatically generated name in user specified directory, when input is from UNIX file, archive tape or raw pass disk.

One or more output tape files, when input is from UNIX file, archive tape or raw pass disk.

If input is from a UNIX file, there will only be one output file. The following input subsectioning options are supported:

Via user supplied start_time and num_lines parameters.

Computing start_time and num_lines based on masterfile coverage.

If the output is to tape, the tape device must support variable length blocks. Commonly used output tape devices are /dev/nrht0 (DAT with APUNIX driver under SunOS 4.1.3), /dev/rmt/0n (DAT or Exabyte under Solaris), and /dev/rmt/0mn (DAT under HP-UX).

PARAMETERS

hrpt_format: OPTIONAL. This parameter defines the format of the raw telemetry to be read. See hrptin NOTES for a list of these formats. The default is auto, which stands for auto-sensing. This parameter must be explicitly specified on the command line.

on_pass_disk: Indicates whether or not input is from raw pass disk. The default is yes.

input_file: Used only when on_pass_disk=no. Specifies the name of the input tape device or UNIX file. A wildcard expression cannot not be used.; If the environment variable TAPE is defined, it is used as the default.

files_per_pass: Used only when input is from tape. Number of tape files per pass, either 1 or 2. If files_per_pass=2, it is assumed that each pass on the input tape is preceded by a header file, and that the input tape is initially positioned at a header file. The default is 2.

pass_year: If on_pass_disk=no, this is the year that the pass was collected. All passes processed in one execution of flac must have the same year.; The valid range is [>=1970]. The default is the current year.

pass_number: Number(s) of the pass(s) on raw pass disk or input tape to be converted to LAC format. Passes are numbered starting with 1. If input is from tape, the tape is assumed to positioned at pass 1. If multiple passes are to be processed from tape, the pass numbers should be strictly increasing.; If input is from tape, the default is 1. If input is from raw pass disk, the default is the number of the most recent online pass.

use_master: Indicates whether or not start_time and num_lines are to be computed based on masterfile coverage. The default is yes.

master_file: Used only if use_master=yes. Name of the TeraScan dataset used to define desired area coverage. The masterfile should have map projection based earth location, rather than on a sensor based.; The default is Master.

start_time: Used only if use_master=no. The start time for data processing. The first line with a time greater than start_time is the first output line. A response of 00:00:00 tells flac to begin processing at the first scan line.; Any valid time is allowed (see formats). The default is 00:00:00.

num_lines: Used only if use_master=no. The maximum number of lines to write to the output dataset. If the end of pass is detected before the output dataset is complete, the output dataset is truncated.; The valid range is [>=1]. The default is 6000.

channels: List of the AVHRR channels to process from the HRPT pass. The five channels correspond to 0.6-0.7, 0.7-1.1, 3.5-3.9, 10.3-11.3, and 11.5-12.5 micrometers.; Valid responses are [1,2,3,4,5]. The default is 1,2,3,4,5.

packed_fmt: Used only when all five AVHRR channels are processed. If yes, output record size is 7400 bytes. If no, output record size is 10464 bytes. The default is yes.

orbit_number: Satellite orbit number for each input pass. Ordinarily TeraScan does not maintain orbit numbers for satellite pass data. If the user knows the orbit number for a given pass, that number should be entered. The default is 0 for each input pass.

EXAMPLES

In the following example output is directed to a file.

C% flac flac.data
on_pass_disk   : char(  3) ? [yes]
pass_number    : int       ? [6] 1
use_master     : char(  3) ? [yes] no
start_time     : char( 15) ? [00:00:00]
num_lines      : int       ? [6000]
channels       : int (  5) ? [1 2 3 4 5]
packed_fmt     : char(  3) ? [yes]
orbit_number   : int       ? [0]
avcal.coef: No date passed for AVHRR calibration table
avcal.coef: Using pre-launch coef's for visible channels
Output starts at time 13:48:39.987, sample 1.
Total of 4093 lines, 6 sync errors, 70 bad times, 51 time gaps.
%

NOTES

There are two LAC records per each AVHRR scan line. The record sizes are listed below:

 	1 channel			 2272
	2 channel			 4320
	3 channel			 6368
	5 channel			10464
	5 channel packed	         7400

For information about EDIS 1B LAC format, refer to the "NOAA POLAR ORBITER DATA USERS GUIDE".

As stated earlier, any output tape device must support variable length blocks. Do not use APUNIX tape devices /dev/nht0 OR /dev/ncht0 for LAC output!

Also, if output LAC tapes are to be sent to other users, keep in mind that not all tape drives support hardware compression.

Last Update: $Date: 2002/05/07 23:19:58 $