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15.2 Visualizing Data from XYZ ASCII Files
Irregularly spaced or gridded data for some quantity Z at given X and Y coordinates are
commonly provided in files using three-columns for the X, Y and Z values, respectively.
Examples of such XYZ datasets are (1) maps of a given Z variable (X represents longitude, Y represents latitude), (2) vertical sections (X=along section coordinate, Y=depth)
or (3) time-evolution plots (X=some geographical coordinate, Y=time or vice versa).
You can load all these XYZ files into ODV and you can analyze and display the Z data using the full suite of ODV functions. Note that the procedures described below can also be
applied to data files with multiple Z variables, e.g., files with more than three columns.
Here is how to proceed if the XYZ file represents a map:
1. Create a new collection (choose a destination directory and collection name)
with just two variables Depth [m] and Z-variable (use a descriptive label and appropriate units for the Z-variable),
2. Import the XYZ file by choosing Import>ODV Spreadsheet and selecting the XYZ
file (note that you have to choose file-type All Files, if the extension of the XYZ file
is not .txt).
3. On the Spreadsheet File Properties dialog specify (1) the column separation character (the items from the header line should appear on separate lines in the
Column Labels list), (2) the line number containing XYZ labels (keep 1, if no labels are provided), and (3) the line number of the first data line,
4. On the Metadata Variable Association dialog associate the X-variable with Longitude [degrees_east] and the Y-variable with Latitude [degrees_north],
5. On the Import Options dialog associate the Z-variable (source) with the second
collection variable (target). Then click on the first collection variable (target),
click on Use Default and specify the default depth value (use 0, if in doubt).
ODV will import the data from the XYZ file, and lets you operate on the data in the usual
way. To create a page with a map of the Z-variable create a data window with SURFACE
scope. Modify the data window’s properties as usual, if this is necessary.
15.3 Overlaying a Property Distribution with Contour Lines of another Property
With ODV, you can produce section or isosurface plots where the distribution of one
property (color shaded and/or contoured) is overlaid with contour lines of another
property. Useful applications, of this technique are, for instance, density contours on
top of any property section or depth contours on isosurface or isopycnal distributions.
To produce such plots, follow these steps:
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Switch to window layout mode via View>Window Layout.
Setup the window for the underlying distribution (window a: define size and position; select a Z-variable for that window (property A) using the Properties option).
Create an overlay window for window a by moving the mouse over window a, click-
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