HRPT formats

HRPT data
HRPT data consists of minor frames of 11090 10-bit words. Each 10-bit word is stored in two 8-bit bytes on disk. Each minor frame corresponds to one AVHRR scan line covering a ground swath of approximately 3000 km. The video data, for the NOAA series of satellites, comprises 5 interleaved channels, each 2048 pixel wide. The SeaWiFS scanner has 8 channels with 1285 pixels per line. As well as video data, each minor frame contains sync, telemetry and TIP data. A full format description is available in the NOAA Polar Orbiter Data Users Guide but we also have a simplified format description.
HRPT data buffered in blocks
Some devices such as tapes find it easier to handle data which comes in fixed-size blocks. Buffered HRPT data is exactly the same as HRPT data above but with the addition of extra zero-filled bytes on the end of each scan line to pad it out to 22 KBytes or 24 KBytes.
HRPT data in packed Dundee format
Dundee format is exactly the same as HRPT data above but packed to save disc space. It stores 3 10-bit words in 4 8-bit bytes, leaving the last (top) 2 unused bits of the fourth byte as zero. Dundee format files are thus two-thirds of the size of HRPT files without any loss of information. Each minor frame is treated separately, and may be padded as described below in the tape formats section.
HRPT data in NOAA Level-1B format
NOAA Level-1B format stores the image data packed and uses the space gained to store better calibration data, geo-referencing data, solar zenith angles, etc. A full format description is available in the NOAA Polar Orbiter Data Users Guide but we also have a simplified format description. Note that the format has been changed for the NOAA KLM series (NOAA-15 and later) so check your software can handle the new format before ordering. It also changed again on 2005/04/01 to format version 3, a notable change being one of the calibration scaling factors.

To process HRPT data you can use:


SeaWiFS formats

HRPT data in NASA SeaWiFS frame-formatter format
SeaWiFS data at level-0 is straight from the satellite but with the addition of a file header and some minor formatting. A full format description is available.
HRPT data in SeaWiFS HDF format
SeaWiFS data at level-1a or level-2 comes in HDF (Hierarchical Data Format). Level-1A packages calibration and navigation information alongside the raw image data whereas level-2 converts the image data into physical parameters such as chlorophyll and CZCS-pigment. A full format description is available in the SeaWiFS Project Software Documentation.

To process SeaWiFS data you can use:


MODIS formats

Downlink data format
The raw data stream from the satellite consists of CADUs of 1024 bytes each containing multiplexed virtual channel VCDUs plus error correction data. xeosdisp is used for viewing this format in real-time during reception. A MODIS packet format description is available.
Level 0 format
Time-ordered, error corrected VCDUs for a single virtual channel, MODIS in this case. Image data can be extracted using eoslzx, please enquire for details.
Level 1 format
HDF-EOS format, an extension of HDF; can be read by eosx, ENVI etc.

To process MODIS data you can use:


CZCS formats

Raw ingested data
See CZCS format.
Level 0 data
Unpacked back to 12375-byte records.
Level 1 data
SeaDAS requires level 1 data. No further information on this format is available.

PDUS formats

Decommutated image files
The received frames are decommutated into one file per channel, with padding for missing/corrupt frames or lines. A full PDUS format description is available.

To process PDUS data you can use:


Image formats

Common image formats
We can supply common formats such as GIF, JPEG, PNG, TIFF etc.
Raw image files
These files have no header or line separators; they are simply the extracted image data as a stream of bytes. You must therefore make a note of the image dimensions for further processing. Pixels in 10-bit data files are stored in two bytes each; you should know whether you require bytes in little-endian (PC) or big-endian (Sun) order.
Calibrated raw files
Sensor-calibrated data can be delivered in raw binary arrays of floating point (real) numbers. These are typically 32-bits (4 bytes) per pixel in either big- or little-endian byte order.
TIP data
The TIP (TIROS Information Processor) data extracted from the HRPT data as 520 8-bit words per line.
CALIB data
The CALIB data extracted from the first 103 words of the HRPT data as 103 10-bit (2 byte) words per line. See HRPT format above.
PGM
PGM files are raw for 8-bit data and ASCII for 10-bit. SeaWiFS data calibrated to level-1b (sensor calibrated radiances) are available in so-called PGM files but the values stored are in floating point format so the file is not strictly PGM but easily readable nonethless.

To process image data you can use:


Tape formats

HRPT (CCT/Exabyte)
Data is stored as received (see above).
HRPT (Cartridge)
Each line is buffered to 22 kbytes by appending 174 words.
Dundee (CCT/Exabyte)
Each line is stored as 4 blocks of 3700 8-bit bytes. Packed Dundee format is described above.
Dundee (Cartridge)
As for CCT/Exabyte but each line is buffered to 14848 8-bit bytes by appending 48 8-bit bytes.

To process tape files you can use:


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