Presentation Layer Protocol

Presentation Layer Protocol

The Presentation Layer protocols are standard protocols employed by the National Oceanic and Atmospheric Administration (NOAA) and the National Weather Service (NWS). They include the World Meteorological Organization (WMO) header and National Environmental Satellite Data and Information Service (NESDIS) header used by the NESDIS products and the Communication Control Block (CCB) and WMO headers used by the NWS Telecommunications Gateway (NWSTG) products. The following paragraphs briefly describe the formats of the various product headers; however, for further details about the protocols one must examine the references given.

NESDIS Products

The Presentation-Level headers for the NESDIS products, as depicted, contain the WMO header followed by the NESDIS header.

WMO Header

The WMO header used by the NOAAPORT Broadcast System (NBS) uses an abbreviated heading for product identification. This heading has the following format:

 T1T2A1A2ii (sp) CCCC (sp) YYGGgg [(sp)BBB] (cr)(cr)(lf)

in which

 T1T2A1A2ii 
= Data designators (sp) = Space CCCC = International four-letter location indicator 
of the station originating or compiling the bulletin YYGGgg = International date-time 
group BBB = Not used for NESDIS products (cr) = Carriage return (lf) = Line feed

and is identified in the AWIPS/NWSTG Interface Control Document (Document Number A0130006).

NESDIS Header

The NESDIS format envelops the visible (VIS), infrared (IR), and water vapor (WV) products and contains the following format:

The header is the Product Definition Block (PDB), which defines the product records. Each record contains one scan line of image data and the end of the image is identified by the end of the block terminator. The details of the protocol and its formats are defined in AWIPS/NESDIS Interface Control Document (Document Number AAO130008).

NWSTG Products

The Presentation-level headers for the NWSTG products, as depicted, contain the CCB header followed by the WMO header. These headers are briefly described in the following paragraphs.

CCB Header

The CCB defines the data formats and/or code forms so that the recipient of the message can determine the proper host processing required to decode the message. The details of the protocol and its formats are defined in reference OFCM Standard Telecommunication Procedures for Weather Data Exchange FCM-S3-1991.

WMO Header

The WMO header used by the NBS uses an abbreviated heading for product identification. This heading has the following format:

 T1T2A1A2ii (sp) 
CCCC (sp) YYGGgg [(sp)BBB] (cr)(cr)(lf)

in which

 T1T2A1A2ii = Data designators 
(sp) = Space CCCC = International four-letter location indicator of the station 
originating or compiling the bulletin YYGGgg = International date-time group BBB 
= This optional group indicates amendments (AMD), corrections (COR), routine delay 
(RTD), or parts (PAA...). (cr) = Carriage return (lf) = Line feed 

and is identified in the AWIPS/NWSTG Interface Control Document (Document Number A0130006).