Parent Topic: Supported File Formats

AVHRR Format

Various AVHRR data formats are supported for reading by the GeoGateway library. AVHRR refers to the sensor on NOAA satellites which produces this type of data.

AVHRR imagery typically contains 5 channels (2 visible channels and 3 thermal channels). Images are either 409 pixels wide (low resolution) or 2048 pixels wide (high resolution).

Supported AVHRR formats include:

Level1b channel selection is supported (Level1b data may contain less than 5 bands).

When FIMPORT is applied to AVHRR data, a text segment containing orbital element values and calibration data is created. For Level 1b HRPT/LAC and GAC formats, a GCP segment containing up to 255 GCPs is also created. For the Level 1b HRPT/LAC and AVHRR CEOS formats, an orbit segment is created. For details please see the subtopic descriptions of the individual file formats.

See Also: AVHRCOR, FIMPORT, MIAVHRR, ORBITWR

LAC/HRPT Level 1b Format
Level 1b HRPT/LAC is high resolution (1 km) data which can be obtained via the World Wide Web (http://www.saa.noaa.gov). The Level 1b designation indicates that this data is an enhanced form of raw HRPT data. Level 1b data contains extra information such as Earth location values in lat/long. This Earth location data is used to form a grid of up to 255 GCPs, which are stored in a GCP segment when FIMPORT is applied to Level 1b data. FIMPORT will also create a text segment which contains information such as the satellite name, date/time of image capture, orbital (ephemeris) element values, and some calibration data.

For the Level 1b HRPT/LAC format, FIMPORT also creates a binary orbit segment containing per-scanline quality, calibration, and timing information.

GAC Level 1b Format
Level 1b GAC data is similar to Level 1b HRPT/LAC data except that it is of lower resolution (4 km).

Dartcom 16-bit HRPT Format
A Dartcom 16-bit HRPT image is stored in the form of six component files. Only the RAW and RPD files are used by FIMPORT. A Dartcom RAW file contains the scanline or video data. This is the file which must be used in conjunction with FIMPORT. The Dartcom RPD file is an auxiliary text file that contains information such as the satellite name, date/time of image capture, and orbital element values. The information from the RPD file (if present) is read into a text segment by FIMPORT. There is no Earth location data in Dartcom RAW or RPD files, hence, FIMPORT does not create a GCP segment for the Dartcom format. A RPD file must have the same basename as the corresponding RAW file, but with a different extension. It must also reside in the same directory as the RAW file.

Satlantic 16-bit HRPT Format
A Satlantic 16-bit HRPT file has a header from which information such as the satellite name and orbital element values can be extracted. This information is placed into a text segment by FIMPORT.

The Satlantic format does not have Earth location information, hence, FIMPORT does not create a GCP segment for this format.

Quorum Qtrack 16-bit HRPT Format
A Quorum Qtrack 16-bit HRPT file begins with two header frames. The first is an "ephemeris data" frame, containing the satellite name and orbital element values. The second is a "start data time stamp" frame, containing the time of image acquisition to the nearest second. The information in these two frames is extracted and placed into a text segment by FIMPORT. The third and subsequent frames in a Quorum file are treated as HRPT scanline frames. FIMPORT does not recognize resync frames in a Quorum file.

The Quorum format does not have Earth location information, hence, FIMPORT does not create a GCP segment for this format.

16-bit HRPT Minor Frame Format
A 16-bit HRPT Minor Frame file contains data (scanline) records, each with a length of 22180 bytes. There is no header record in this format. This format does not contain any information about the year of image acquisition, hence, this quantity will not be available in the text segment created by FIMPORT.

The HRPT Minor Frame format does not have Earth location information, hence, FIMPORT does not create a GCP segment for this format.

Dundee 16-bit HRPT Format
A Dundee 16-bit HRPT file has a header from which information such as the satellite number and year of image acquisition can be extracted. This information is placed into a text segment by FIMPORT. The header has a length of 22180 bytes.

The Dundee format does not have Earth location information, hence, FIMPORT does not create a GCP segment for this format.

AVHRR CEOS Format
The AVHRR CEOS (Raw AVHRR CCT Image Format) is supported. The specifications for this format are outlined in the following document: 

 DMD-TM #90-678F
 "Standard Raw AVHRR CCT Image Format Specifications"
 Canada Centre for Remote Sensing
Typically, AVHRR CEOS data exists in tape format. A single CEOS scene consists of 5 tape files: volume directory file, leader file, image file, trailer file, and null volume directory file. It is possible to transfer the 5 tape files corresponding to a single scene into 5 disk files. In order to import the 5 disk files corresponding to a CEOS scene, it is necessary to supply the volume directory file as the input file (FILI parameter) and ensure that the 5 disk files follow the appropriate naming convention. As an example, these are the names of 5 disk files corresponding to a CEOS scene: myscene.vol, myscene.led, myscene.img, myscene.trl, and myscene.nul. Note that only the volume directory file and image file are mandatory. All of the files corresponding to the same scene must reside in the same directory.

For the AVHRR CEOS format, FIMPORT creates a binary orbit segment containing per-scanline quality, calibration, and timing information.

Some Definitions
Parent Topic: Supported File Formats
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