SeaDAS Help - Data Processing Tools

l1aextract_modis

Creates an extracted L1A MODIS file.

Location

Tools -> OCSSW Processing -> l1aextract_modis

Details

l1aextract_modis extracts a MODIS Level 1A sub-scene from an input Aqua or Terra L1A and GEO file. Users can specify a sub-scene either using longitude/latitude of southwest and northeast corners (swlon, swlat, nelon, nelat) or using start/end pixel numbers in conjunction with start/end lines. The former is referred to as lon/lat arguments and the latter is referred as pixel arguments. Once a user choose to specify the sub-scene using the lon/lat option, all four arguments must be specified. The program will fail to extract if any argument is missing.

Alternatively, users can directly specify pixel arguments to extract a sub-scene.

**l1aextract_modis GUI**

Arguments/Keywords

UI Element Name	Type	Description	Required/Optional	Default Value
infile	Text Field	Input MODIS Aqua or Terra L1A file to be extracted, or an L1A filelist for multiple file extraction. (Required)	Required
ofile	Text Field	Output filename for the L1A extracted subscene. A default ofile name is generated by the program.	Required
swlon	Text Field	Longitude of southwest corner of the box to be extracted.	Conditional
swlat	Text Field	Latitude of southwest corner of the box to be extracted.	Conditional
nelon	Text Field	Longitude of northeast corner of the box to be extracted.	Conditional
nelat	Text Field	Latitude of northeast corner of the box to be extracted.	Conditional
spixl	int	Starting pixel in infile for extracting.	Conditional
epixl	int	Ending pixel in infile for extracting.	Conditional
sline	int	Starting line in infile for extracting.	Conditional
eline	int	Ending line in infile for extracting.	Conditional

Actions/Buttons

UI Element Name	Type	Description
Browser Button	Button	Selects infile/ofile
Compute PixLines from LonLat	Button	Derives spixl, epixl, sline, and eline arguments from swlon, swlat, nelon, and nelat arguments by internally executing the lonlat2pixline program.
Load Parameters ...	Button	Reads in previously saved parameters and populates the fields in GUI.
Store Parameters ...	Button	Saves the current arguments in GUI in a file.
Run	Button	Executes the l1aextract_modis command with arguments provided in the UI.
Cancel	Button	Closes current processor GUI.
Apply	Button	Makes current arguments effective.
Open in SeaDAS	Checkbox	If selected, the ofile will be added to the open products list right after its generation.
?	Button	Displays the help content of the current command.

Command Line Usage

Usage: l1aextract_modis infile spixl epixl sline eline outfile
   where:
        infile   - input MODIS L1A datafile
        spixl    - start pixel number (1-based)
        epixl    - end pixel number (1-based)
        sline    - start line (1-based)
        eline    - end line (1-based)
        outfile  - output file name

Note: Enter line number NOT scan number!