prepared by

(Data Processing Consultant, Dar-es-Salaam, Tanzania)


The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Meteorological Organization concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries.

The report has been produced without editorial revision by the WMO Secretariat. It is not an official WMO publication and its distribution in this form does not imply endorsement by the Organization of the ideas expressed.


1. Introduction
2. Data Communication Technologies
2.1 Networking
2.1.1 The OSI Model Connection Services: Layers 1-2 Transport Services: Layers 3-6 Application Services: Layer 7
2.1.2 Network Classification Geographical Area Coverage Resource Distribution
2.2 The WMO GTS
2.2.1 Satellite-based Platform
2.2.2 Ground-based Platform
2.3 The Internet
2.3.1 Internet Resources
2.3.2 Resource Transport IP Address Domain Name Universal Resource Locator (URL)
2.3.3 Resource Storage Server Type Server Connection to Internet
2.3.4 User Access to Resources Dial-up Terminal-Type Connection Dial-up TCP/IP Connection Connection Over Internet Network
2.4 Internet Security
2.4.1 Cryptographic
2.4.2 Firewall Proxy Servers Routers
2.4.3 Physical Isolation
2.4.4 Protocol Isolation
2.4.5 Protocol Isolation with Server Replication
2.4.6 Multi-homed System with Routing Disabled
2.4.7 Tunelling Through the Internet
3. System Vision
3.1 System Concept
3.2 Considerations
4. System Design


Communication Link Sub-System
4.1.1 Satellite Communication Links
4.1.2 Terrestial Communication Links
4.1.3 The X.25 and IP Protocol
4.1.4 The Role of Internet in the GTS Application of Internet Technology within GTS The GTS Completely Turned Over to Internet A Mix of GTS and Internet
4.2 The Automatic Message Switching (AMSS)  SubSystem
4.2.1 AMSS Data/Products Reception
4.2.2 AMSS Data/Products Transmission
4.3 Database Management Systems (DBMS)
4.4 Products Generating System
4.4.1 The Plotting Module
4.4.2 The Climatological and Database Management Module
4.4.3 The Media Module
4.4.4 Operational Weather Forecasting Module
4.4.5 Numerical Weather Prediction (NWP) Module
4.4.6 Internal Internet Web Server Module
4.5 Protecting the GTS
5. The Recommended Computerized Data Handling System
5.1 The Basic Computerized GDPS System
5.1.1 Hardware
5.1.2 Software
5.1.3 DBMS System
5.1.4 Training
5.2 Migrating Towards the Desirable GDPS System
5.2.1 The GTS Circuits
5.2.2 The Application Sub-system
5.3 The Basic Internet System
5.4 The Desirable Internet Connection
5.5 Remote Access Services (RAS)
6. Cost
7. Training
8. Concluding Remarks
9. References
10. Annexes
Annex 1 The Basic NMC Computerized Data Handling System
Annex 2 A Simple Remote Access Services (RAS) Configuration
Annex 3 The Desirable NMC Computerized Data Handling System
Annex 4 The Multi-user Dial-up Internet System
Annex 5 The Desirable Internet System
Annex 6 Estimate Costs of Typical Packages
Annex 7 PC System Specifications
Annex 8 Some OSI Model Implementation


For the NMCs to carry out their work they need data and/or products. The data is obtained from their national observing stations, the Regional Telecommunication Hubs (RTHs), meteorological Satellites and through bilateral arrangements with neighbouring NMCs and other Institutions. The products are mainly received via meteorological satellites but can also be received via fax and Internet.

The data so collected is quality controlled and further processed to produce national products. The national collectives are also injected into the WMO Global  Tele-communication System (GTS) for onward transmission to the RTH and/or other NMCs. The NMCs prepared products may also be communicated to national "zonal offices." With regard to received products, the NMC would further process these to derive value-added products which are used at the NMC and at its zone offices.

In pursuit of carrying out these functions NMCs in RA I have, over the years, invested heavily to implement a robust operational regional data handling infrastructure - an infrastructure which includes the data observing system, data collection, tele-communications and data processing facilities. The National Meteorological Centres (NMCs) expected returns from this investment includes the timely preparations of national products from local data and/or imported products to service the national needs and the capacity to transmit or re-transmit such data and/or products to other NMCs.

However national and international requirements are constantly expanding in volume and sophistication; the NMC have to respond to these changes, national financial constraints notwithstanding, by further investments in:

The twelfth Session of RA I (Arusha, 14-23 October 1998), tasked the Working Group on Planning and Implementation of World Weather Watch (WWW), among other things are the following:

Pursuant to these tasks, a detailed specification for organizational and implementation aspects of the GDPS infrastructure at NMCs in RA I which include suggestions of cost effective systems for the modernization of data processing facilities, related telecommunication interface facilities for data collection , quality control of data and post processing of imported products to generate value added products meeting national and other users requirements are being provided in this report.