Power OceanAtlas General Information

Power OceanAtlas Introduction Power OceanAtlas is an application for Macintosh OS microcomputers which provides a graphic exploration environment to examine and plot oceanographic section data. Power OceanAtlas 1.2 is a new enhanced version of OceanAtlas. This is a companion to the IBM-PC program Atlast developed by Peter Rhines, but OceanAtlas and Atlast are different applications sharing common roots, not Macintosh and PC versions of the same application. Power OceanAtlas can function as a stand-alone living atlas of oceanographic sections: the initial data set supplied includes bottle data for P, T, S, O2, NO3, PO4, and SiO3 from major trans-oceanic sections. Additional sections of arbitrary parameter composition can be added to the data base at any time via the supplied application OceanAtlas Convert 2.1, and by direct reading of spreadsheets and WOCE or NODC format bottle data files. Power OceanAtlas will work with any type of pressure-indexed data. Power OceanAtlas plots include offset profiles, property-property plots, contour plots, and 3-D plots, using color as a third (or fourth) plotted variable to aid interpretation. There are also station position maps and a comprehensive data display window. All Power OceanAtlas plots are linked and may be 'browsed' by sample and/or by station. Plots can be re-scaled, resized or have their colored variable changed. Selected areas of profile and property-property plots can be made into new plots. Standard levels, scales, contours, and colors can be changed via user interfaces similiar to those used in commerical Macintosh applications. Power OceanAtlas provides data filtering, exporting, and editing. Many different types of calculations can be performed, including anomalies and geostrophic velocities. The OceanAtlas electronic atlas of oceanographic sections provides a unique reference and teaching environment. Power OceanAtlas is also a powerful data examination tool, and as such is useful for initial exploration and data quality examiniation of new expedition data. top

Power OceanAtlas General Information

What Power OceanAtlas Does Best Power OceanAtlas (POA) is great property-property plots, allowing any original or calculated parameter to be plotted against any other. There is full control over axis ranges, plot point size, etc. plus the plotted points can be colored by any other parameter for which there are values and a color/contour bar. And by selecting "Connect Observations" from the Goodies menu, on each property-property plot a line will be drawn connecting the values in sequence. Profile (waterfall) plots are another high point. These too are colored by the current color/contour bar, and a real bonus is that if the profiles are made 'flat' (amplitude=0) and 'fat' (width and spacing adjusted to fill the space between successive profiles with color), you get a full-color section of whatever variable is represented by the current color bar. (Hint: Because there are almost always temperature data, zero-amplitude profile plots are best made using TEMP as the X-axis parameter so that missing data do not unnecessarily clutter the profiles.) POA is an excellent data exploration tool: click the mouse pointer on a data point on one plot and it gets highlighted there, on all other open plots (including Maps and Contour plots too), and the actual data are displayed in thedata window. By using Filters and appropriate plot scales to focus on the data of greatest interest one can get drawn into the data. POA is not bad at Contour plots. (Hint: You must interpolate data onto standard surfaces before Contour plots can be made. Use the "Vertical Interpolations" dialog box under the Calculations menu. Then your interpolations will be available under the Plots menu in the "Contour Parameter" sub-menu.) The new 3D plots are both fascinating to study and difficult to interpret. Try them! Any number of sections can be combined, or subsets made from sections and re-combined, etc. to cover whatever area you wish. This can be very useful. top

Power OceanAtlas General Information

Limitations of Power OceanAtlas Power OceanAtlas is a section-oriented application, and we have organized the data sets we include by section. Mainly Power OceanAtlas does not support horizontal mapping (except for station positions). There are good reasons for this, mostly having to do with data density, data noise, and the limits of gridding algorithms. We have experimented with an OceanAtlas version which makes contoured data maps, but while it worked find with carefully prepared pre-gridded data, it left much to be desired for the mixed data which goes into most basin-scale maps such as those made by Prof. Joseph Reid of SIO. So we focused our efforts on building on the strengths of the original concept. Power OceanAtlas was not made as a presentation/publication plot tool. Other programs are better at that, although some interesting presentation-quality graphics are possible by using a screen capture utility or the clipboard to grab POA plots and copy them into a graphics program for enhancement and printing. For best results use a methodology which works in PICT rather than bit map format. The gradient/flux/transport calculations and related plots remain somewhat obtuse. Frankly, we would never use POA to calculate velocities,fluxes, and transports except as an exploratory tool. The interfaces for these are OK for knowledgable oceanographers. Many users report problems converting their own data files with OceanAtlas Convert 2.0. One problem was that many of the distributed copies of OA Convert 2.0 were defective. (Sorry!) But conversions are never easy for novice users. (We have included some guide documents.) Our response, in addition t repairing Ocean Atlas Convert, was to increase the ease of direct data import within Power OceanAtlas, which accepts spreadsheet, WOCE, and NODC SD2 format data. 3D plot performance is so dismal on "68K" versions of POA - especially the "no fpu" version (even running in emulation on a PowerPC 604/150 MHZ Mac) - that we considered the extra work of disabling them. If you are a frustrated POA 3D plot user on a 68k Mac, before you throw our POA just try the PPC version on a PPC Mac. The difference in 3D plot performance is amazing. top

Power OceanAtlas General Information

Loading Requirements If you have a PowerPC-equipped Macintosh you should use Power OceanAtlas 1.2 (PPC). If you have a 680x0-equipped Macintosh with the floating point processor you should use Power OceanAtlas 1.0(68kfupu). (These Macs will also run the "no fpu" version, but much more slowly.) If you have a 680x0-equipped Macintosh without the floating point processor, you should use Power OceanAtlas 1.0(68knofpu). top