Presentation on theme: "FM 94 BUFR and FM 95 CREX Table Driven Code Forms (or “Self-descriptive” Code Forms). The term "self-descriptive" means that the form and content of the."— Presentation transcript:
FM 94 BUFR and FM 95 CREX Table Driven Code Forms (or “Self-descriptive” Code Forms). The term "self-descriptive" means that the form and content of the data contained within a BUFR or CREX message are described within the BUFR or CREX message itself. In addition, BUFR offers condensation, or packing, while the alphanumeric code CREX provides human readability.
BUFR (Binary Universal Form for Representation meteorological data) – binary data format CREX (Character form for Representation and EXchange of data) – character data format
BUFR was first approved for operational use in 1988. Since that time, it has been used for satellite, aircraft, wind profiler, and tropical cyclone observations, as well as for archiving of all types of observational data. ============================================== In 1994, CREX was approved as an experimental code form by the WMO Commission on Basic Systems (CBS Ext.94). In 1998, CBS (CBS-Ext. 98) recommended CREX be approved as an operational data representation code form as from 3 May 2000. In 1999, this recommendation was endorsed by the WMO Executive Council (EC-LI (1999)). CREX is already used among centres for exchange of ozone, radiological, hydrological, tide gauge, tropical cyclone, and soil temperature data. ============================================== BUFR should always be the first choice for the international exchange of observational data. CREX should be used only when BUFR cannot. ============================================== BUFR and CREX are the only code forms the WMO needs for the representation and exchange of observational data and are recommended for all present and future WMO applications.
Differences BUFR offers data packing. Therefore, voluminous data (e.g., satellites, ACARS, wind profilers,…) will require fewer resources for transmission and storage than CREX. BUFR also permits the transmission of quality information with the original observational data. However, BUFR data is not human readable. Because it is not human readable, BUFR processing assumes the availability of well designed computer programs to process (decode or encode) the messages. CREX is simpler than BUFR and consequently easy to understand, to code and, because it is an alphanumeric code form, to read with only several hours of explanation. It is therefore particularly useful where computer equipment is not available. However, CREX does not offer packing, and has much less comprehensive capability for including quality information than BUFR.
Main Advantages Partial self-description Universality Expandability Data packing (for BUFR) Data readability (for CREX) ================================= BUFR and CREX are recommended for all current and future WMO applications
Structure of BUFR report Непрерывный поток двоичных данных Секция 0Секция 1Секция 2Секция 3Секция 4Секция 5
Содержание секций формата BUFR Sec.#НазваниеСодержание 0BURF индикатор1) Термин "BUFR" (в коде АSCII); 2) длина всей телеграммы; 3) номер редакции кода BUFR 1идентификация данных в телеграмме 1) Длина секции; 2) идентификация данных в телеграмме 2Факультативная секция 1) Длина секции; 2) дополнительные данные для локального использования Центрами Обработки Данных 3Описание данных1) Длина секции; 2) число подмножеств в секции данных;, 3) флаг категории данных; 4) флаг сжатия данных; 5) набор описателей данных, которые (описатели!) определяют форму и содержание каждого элемента секции данных 4Секция собственно данных 1) Длина секции; 2) двоичные данные наблюдений 5Заключительная секция "7777" (в коде ASCII)