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McIDAS Programmer's Manual

Preface

McIDAS (Man computer Interactive Data Access System) is a set of tools for obtaining, analyzing, displaying and integrating environmental data. Its design focuses on four attributes:

the scientific use of time-sequential satellite data
the merging of diverse databases
access to real-time databases
support for the operational and research user community

The Space Science and Engineering Center (SSEC) of the University of Wisconsin-Madison has actively developed McIDAS software since the early 1970s.

McIDAS was originally developed on a Raytheon-440 computer using punch cards, paper tape and magnetic tape. It provided animation, display and analysis of geostationary meteorological satellite data. Later, the code was moved to Harris minicomputers in a distributed network, with two data servers and several applications boxes. Radar, meteorological observations and forecasts were added to the system. McIDAS' ability to provide real-time access to satellite and conventional data made it appealing to the meteorological forecast community.

As the amount of McIDAS code grew, it needed more processing power to ingest data, run larger applications and simultaneously serve more users. Thus, it was centralized onto an IBM mainframe running the MVS operating system.

Prior to McIDAS-MVS, workstations connected to the mainframe were considered dumb with most processing done on the mainframe. The workstation handled only simple controls such as changing frames, activating looping and positioning the cursor. With McIDAS-MVS in place, the first smart workstation was developed on DOS-based personal computers. These machines front-ended display hardware, such as the tower workstation. There were very few local applications, since the necessary multitasking was simulated in the McIDAS software.

The first large-scale port of applications software occurred when the OS/2 operating system was embraced for PCs. This was the beginning of McIDAS-OS2. Efforts to create an environment similar to the mainframe resulted in a smooth port of many applications. However, some changes were needed to accommodate special hardware; for example, VGA displays had only 16 color/gray levels. In addition, drivers were written for each display head: VGA, tower, WIDE WORD and SDA. These drivers had to appear to the applications as the same kind of raster-oriented device, with some varying characteristics such as frame size and number of colors. Communications drivers satisfying all applications were also needed for the common modes: asynchronous, ProNET and TCP/IP.

McIDAS-OS2's success led to the migration of McIDAS to the Unix environment. McIDAS users wanted support for applications on these faster, larger hardware platforms. The first attempt at this migration was taking the OS/2 code and writing specialized routines for the keyboard, mouse, text display, and image/graphics display, plus the system-level interfaces required for communications and disk I/O. The result was McIDAS-X.

Except for the ASK command and the Graphical User Interface, the implementation of McIDAS-X was done using the X Window System. To support McIDAS-X on more platforms and have it adhere to industry standards, the base code was changed significantly to make it more portable and less platform- and vendor-dependent.

Today, McIDAS is a fully distributed, workstation-based system. It generates multicolored composites of conventional and satellite weather data in a variety of displays in two and three dimensions as well as time-lapse sequences of these analyses. Designed to handle large amounts of meteorological imagery and other atmospheric data in a convenient manner, the system provides a vast resource of image-processing and applications programs. McIDAS hardware and software is used worldwide.

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