About Atlases

P. Rhines and J. Swift

Today's desktop computers offer us the facility to hold and examine large quantities of ocean data in a way that uniquely supplements paper atlases. George Batchelor speculated (J. Fluid Mech. 1981) that computers would not replace paper journals: "Personally I should regret the introduction of any system which did not allow me to hold in my hand and take in a quiet corner of my own choice, a thing like a book with paper pages which are printed in attractively designed type." Many of us feel attached to paper for the simple reasons of stability and annotation: it is difficult to read something profitably without marking it all up, and one wants it to be around for at least ten years, probably more. But much of the hard-won accuracy and breadth of ocean data is lost on the way to the journal page.

The way we form ideas and paragraphs with a fast word processor is remarkably different from the original pen and ink process. The computer, once just a calculator, has enabled us to work in new ways. Similarly, the computer can enable us to examine data in new, flexible ways, and, rather than replacing traditional atlases, permits us to take new directions.

While traditional temperature and salinity measurements remain the heart of physical oceanography, we are rapidly being drawn into areas where new variables are important: trace chemistry, biology, three-dimensional distributions of atmospheric variables and sea surface imagery. This surge of data requires a new approach. Perhaps the oldest problem in oceanography is the unanalyzed or under analyzed data set. This may become far worse with so much effort going into ocean data collection in the 1990's. A modest contribution toward solving this problem would be a simple means by which a new ocean section could be sent through the mail and immediately viewed, 'picked up, and turned over' using widely available hardware. That is one intent here. Another intent in this work is to provide an educational tool for ad hoc real-time visualization of oceanographic data, to permit casual, easy exploration of the oceans at low cost and in new ways.

Stommel and Fieux (1978, Woods Hole Press) present us with a Guide Michelin of ocean atlases. This little book summarizes the paper atlases available then. Most oceanographers spend time with these atlases and they are wonderful to have at sea on a cruise, to provide a context for a new section or perhaps a new type of measurement that the authors of the atlas never could have envisaged. But they are frustratingly rigid in their presentation, preventing us from making new connections and comparisons by simple scale changes, or changes of plot variable. Many oceanic variables are being measured on cruises like the Transient Tracers in the Oceans (TTO) and the World Ocean Circulation Experiment (WOCE); the potential number of property-property plots with, say 15 variables, is large, and with plots using 2 dimensions plus color, or even 3 dimensions plus color, we have nearly limitless possibilities.

Computers have been used to plot and analyze data since their inception (an example is Fofonoff's early (J. Fish. Res. Bd. Can, 1962) analysis of northeast Pacific wind-stress curl which, he admits, was initiated to find a use for the new computer at Nanaimo: he may be the first oceanographic computer junkie). Individual groups with a collection of stations have often produced efficient plot software. Those who have major ocean-going projects have thus developed their own systems. Some of these, like the acquisition and plot programs of the Oceanographic Data Facility group at Scripps, or the section contouring applications developed by Dean Roemmich and Lynne Talley, are remarkably facile. These systems are currently on Sun desktop systems. Electronic atlases are a slightly different concept. Tom Sgouros and Tom Keffer at Woods Hole in the mid 1970's wrote a program called CAMS-ATLAS for VAX machines. This program allowed the user to assemble data from the attached disk archive, and plot and contour sections, property-property plots, map variables on a horizon of choice (like sigma-theta). Part of the goal was to make the first extensive set of potential vorticity maps.

These and other 'expert' systems, now typically on UNIX workstations, will remain the key tool of the deep-sea oceanographer. Nevertheless there are many who do not spend their full time overseeing such data sets, yet need to use them just as one needs an atlas. They (and perhaps even the experts) need a facile way of participating in the stream of new data, and in trading it around. And one wants the data 'in entirety', without degradation of accuracy, not an internal report synopsis or the output of an inverse calculation of uncertain quality. We at last have been given the power to examine hydrographic and tracer data without building a massive effort of computing and plotting.

These matters must have been in the minds of Stommel and Luyten (WHOI Tech. Report, 1989), when they produced a set of North Atlantic data on floppy disks. They combined the data set with an elegant 120-line Basic program, PLOTTER.BAS, to view them with.

The program ATLAST [for IBM-PC's] took the example of these earlier efforts, and developed the goal of 'browsing' the data, zooming in so that the full accuracy can be accessed, and replotting in ways which are natural. Its object is not only to improve the convenience of conventional data plotting, but to suggest new kinds of analytical plots.

ATLAST stimulated the development of OceanAtlas for Macintosh, now called Power OceanAtlas, which works with ocean section data. Power OceanAtlas provides a set of simple tools to examine on screen whatever data facets and features are of interest to the examiner. Power OceanAtlas links the browsing features of all plots. Like ATLAST, Power OceanAtlas is not a data presentation program, but is more nearly an ad hoc real-time data exploration program.

The program Ocean Data View [for IBM-PC's running Windows 95 or Windows NT] includes a wide array of property-property, section, and areal plots, and supports hardcopy output. It is somewhat less oriented toward data exploration than are ATLAST and Power OceanAtlas, but can produce stunning plots.

We hope that you enjoy using the software on your PC or Mac to examine these data.

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