Processing, Compression and Transmission of Satellite IR Data for Near-Real-Time Use at Sea

Abstract

A method for acquisition, processing and analysis of digital, satellite-derived SST fields on a research vessel at sea in near-real-time (within 10 h of the satellite pass) is discussed. Such imagery provides a general view of the SST field over a large area (700 × 900 km) centered on a 128 × 128 pixel, full-resolution view of the study area. The ability to send these images to the research vessel in a reasonable amount of time (about 1 h using ATS-3) was a result of a three-level approach to data compression. To perform data compression, first, the overall image was decimated by 2 while the central 128 × 128 pixel portion was retained in full resolution. Second, a 1-bit-deep cloud mask was derived from the image. Third, the remaining SST values were encoded as SST steps from the previous pixel on a given scan line. Overall, the data were reduced by 75%–80%. An error-correcting protocol KERMIT, was used to establish low error rate data communications through the ATS-3 VHF links. A moderate capability digital display unit facilitates display and manipulation of the resultant imagery.