Saturday, December 10, 2011

Bathymetry in 3D

NOAA Portsmouth Harbor Bathymetry
Using depth data collected from sonar measurements, oceanographers create bathymetric charts showing physical features of the ocean floor. During our physical oceanography studies, students create both two-dimensional and three-dimensional bathymetric charts using depth data collected from "mystery boxes" containing models of various ocean features. During the lab activity, students complete the following tasks:
  • Collect depth data in rectangular grid patterns across the mystery boxes
  • Draw and colorize isobaths (lines of equal depth) to delineate areas of similar depth
  • Identify names of the ocean features found inside the mystery boxes
  • Create 3D surface charts from the data to finally "see" what's inside the mystery boxes
At the beginning of the lesson, students are rather daunted when I tell them they will be creating a 3D bathymetric chart. By the end of the lesson, they are quite proud of their accomplishments.

To create the final 3D bathymetric chart, students enter their data into Microsoft Excel and use the surface chart option to visualize a realistic model of their original mystery box. Just as we cannot lift the ocean to see the features below, students may never open the mystery boxes to see what's inside—they are reliant upon their data and 3D models to "see" the ocean floor.

The process for creating a 3D surface chart in Microsoft Excel (2007 and 2010 versions) is outlined as follows:
  1. Type in all of the bathymetry data (including grid numbers) and select it
  2. Go to Insert tab on the ribbon
  3. Click "Other Charts" and select "3D Surface Chart"
  4. Move Chart to "New Sheet"
  5. Right-click the vertical (value) axis and choose "Format Axis"
    • Change Maximum to "Fixed" and enter the maximum data value
    • Change Minimum to 0 (sea level)
    • Change Major Unit to "Fixed" and enter a value of 5.0 (the isobath interval)
    • Check the "Values in Reverse Order" box
    • Close
  6. Right-click the horizontal (category) axis and choose "Format Axis"
    • Check the "Categories in Reverse Order" box
    • Close
  7. Right-click the chart and choose "3-D Rotation"
    • Use the arrows and options to adjust the chart to a nice view
    • Close
  8. Click the entire legend ONCE to select it. Then click ONCE on an individual color in the legend to select it by itself.
    • Right-click that color and choose "Format Band"
    • Experiment with either the Solid Fill or the Gradient Fill to create a nice blend of colors from deep to shallow
    • Close
  9. Format the rest of the chart as necessary to include items such as a descriptive title, axis labels, and a well-written caption
  10. Add clip art and images to create a unique, eye-catching final style for the 3D chart
See the results below...

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