NOAA data compression using a multi length DPCM code and a variable length code NOAA data compression using a multi length DPCM code and a variable length code
Byoung Sun Kim, munekazu Sakamoto, Mikio Takagi
Institute of Industrial Science University Of Tokyo
Abstract
In this paper wee purpose a method to compress meteorological satellite NOAA advanced very high resolution Radiometer data and the result of experiments we examined the entropies of each channels and the correlation between channels .The method is based on differential Pulse code Modulations and Multi length code and a variable length code by Wyle code of hasler code and once. The interchange prediction reduces the total entropies to about 10% of the intracranial prediction though the multi length code shows lower efficient than the variable length code if code words fit in byte and word boundaries the handling of the code words on a computer becomes more convenient using a variable code with inter channel prediction the average compression is slightly under a half of the original data.
Introduction
The remotely sensed data from NOAA can provide very useful and important information in Meteorology Ocean graphy and many other scientific fields because of its simultaneous and repeated broad area observation of the earth. We receive 4~8 scenes a day from two NOAA which are restored on the recorder tapes CLS and the optical disc. However the image data is enormously large AVHRR data account for about 51:2 ~ 57.5 MB channel X10bit for 2048X4000~4500pixels) on the one pass data of 63 MB so we must devise an information preserving compression technique to keep our archival system compact. Data compression has important application in the areas of the data transmission and data storage. Compression data to be stored or transmitted means increasing the capacity of the communication channel. Similarly compression a file for scene to the half of its original size is equivalent to doubling the capacity of the storage we are obliged to store the data at a higher thus faster and reduce the load on the input and out put channels of the our archival system.
In this paper we purpose a method to compress NOAA -AVHRR data with the result of the experiment. We examined the entropies of each channels and the correlation between channels to know the co0mpression limits we employ DPCM and a code based on multi length code word of bit and a variable length code by wyle code B2 code of hasler code and once Iwastia code.
Outline of NOAA AVHRR
The meteorological satellite NOAA-10 NOAA-11 goes around the earth at the average altitude of 810km in about 101.2 minutes and we can get the observation data about 13
Table: 1 Spectral characteristics of AVHRR
| Channel |
wave length |
Primary use |
| 1 |
0.55.~0.68 |
Day time cloud and surface mapping |
| 2 |
0.73~1.10 |
Surface water delineation |
| 3 |
3.55~3.93 |
Sea surface temperature night time cloud mapping |
| 4 |
10.5~11.5 |
SST. day/ night cloud mapping |
| 5 |
11.5~12.5 |
SST |
figure1: The Entropies of each channel
minutes when it passes the highest orbit. We convert the received raw. Data stream into 16-bit word so that the handling of the data on a computer becomes more convenient. Advanced very high resolution Radiometer data account for about 51.2~57.5 MB on the one pass data of 63 MB one pass data of 63MB is changed the 100MB and we receive 4~8 scenes a day from two CLS the optical disc AVHRR of NOAA is four or five channel scanning radio meter instrument the fifth channel data is the same as the fourth on e so that the same for both the four or five channel version table show the spectral characteristics of each channel.
