Explanatory Notes

Sample data provided here are 1) those of HRIT and LRIT images both of which are to be disseminated from MTSAT-1R, and 2) those of HiRID images which are compatible with S-VISSR image of GMS-5.

1. How image data are processed (HRIT and LRIT)

The observation data obtained with the MTSAT series are made into

• - raw data covering full disk or hemisphere (for LRIT, reduced data with less brightness levels and partly limited in area take the place of raw data; hereinafter referred to as "reduced data"), as well as
• - its file header which includes information such as image structure, image navigation and image data function that relates output of the imager to temperature.

A "compressed image data" are made from the above
1) compressed "raw data" portion and
2) its file header. JPEG algorithm (lossless or lossy compression) is used for above compression of raw data.
For explanation of file headers of the sample image data, please refer to HRIT_LRIT_Header_Information.PDF or HRIT_LRIT_Header_Information.xls.

2. Necessary processes at the ground station to use image data (HRIT and LRIT)

After receiving the image data, i.e. "packet sized data", first, you need to decode it to obtain "compressed image data."
Then, you need to decompress the imagery portion of the above "compressed image data" with JPEG algorithm to obtain "non-compressed image data."

3. Use of sample data

These sample data can be used for verifying functions, such as decompression of "compressed image data", of concerned software/hardware of a receiving equipment. All sample data are made from infrared image observed with GMS-5. Please note that "compressed image data" made by lossy compression cannot be decompressed to original data completely.