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Exercise Title: Exporting Marine Data from Ocean Data View (ODV): Interpolations
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Abstract: In this exercise you'll learn an alternate method to obtain ocean station data, selected for any depth (or other defined surface) from an ODV collection. This method can be used instead of the data subsetting method that selects data within a given range of depth values (or other defined surface). The result is a tab-separated TXT file that can loaded directly into most GIS systems.
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Preliminary Reading (in OceanTeacher, unless otherwise indicated)
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Required Software:
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Other Resources:
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Author: Murray Brown
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Version: May 2013
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| 1. Make sure the above collection is currently viewing this VIEW: temp_interp_0m_jfm_liberia_wod (one of those made in the previous exercise). If you intend to edit the data, to remove outliers by setting ranges or other sample and selection criteria -- as shown in Creating Marine Data Surface Plots in ODV -- then do it now before you continue this exercise. |
| 2. You should be seeing approximately this view of a surface mode product; in this case JFM for 0 m. |
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3. The gridded analyses that ODV can make (with its QUICKGRID, VG GRIDDING and DIVA gridding methods) are not optimized for translation to GIS systems. But the interpolated variable values made in surface mode are easy to obtain. The sample data produced in the exercise Exporting Marine Data from ODV: Data Subsets are exact copies of values in the original station data, within user-specified depth limits. The "data" visualized in surface mode depth-defined product (e.g. the above image) are interpolated from values just above and just below the desired depth. These interpolated values are exported in this exercise, and can be used as an alternative to the data subsets. This is purely optional.
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| 4. Right-click on the image, and select PROPERTIES > DISPLAY STYLE > ORIGINAL DATA to remove the data grid and show the original location plot. |
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| 5. When the Greenwich Meridian is included in the area of interest, then data exported with the method shown below have longitudes in the -180 to +180 system. Otherwise, they are in the 0 to 360 system. As a general principal, you should apply the next two steps to make certain that you get the desired -180 to +180 data, especially if your area of interest is in the western hemisphere. |
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6. Right-click on the graphic and select SET RANGES. Then change the longitudes and latitudes exactly as you see here. Then click OK.
NOTE: No, you can't simply enter the Liberia AOI coordinates...this doesn't work.
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| 7. Here you see the data area greatly reduced. But the geographic coordinates are now GIS-compatible. |
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| 8. Right-click on the graphic and select EXTRAS > CLIPBOARD COPY. |
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| 9. Make these settings. Then click OK. |
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| 10. The interpolated station data are not in a file yet. They are in the clipboard, and must be pasted into a file. Click OK. |
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| 11. Run the ASCII editor ConTEXT or NotePad++. Then use PASTE to insert the interpolated data into a new empty file. |
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12. Here's what the file looks like now. These are interpolations, not original data.
NOTE: If the longitudes are not in the -180 to +180 system, then go back to Panel 6 and repeat the step.
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| 13. Use the editor's save function to save the file to the folder PRODUCTS > ODV > INTERPOLATIONS with the filename temp_interp_jfm_0m_liberia_wod_odv.txt |
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14. Go back and repeat all of the above steps, with appropriate changes of the views, to obtain the files you see here.
Remember:
- To change the depths, you change the Z value from the surface analyses.
- To change the months, right-click on the little station map and use STATION SELECTION CRITERIA.
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| 15. Now these TXT files can be used in Saga gridding, instead of the data subset spreadsheets from Exporting Marine Data from ODV: Data Subsets. You simply substitute these tables into Converting a Data Table to a Point Shape in Saga, and continue on with Gridding Point Shapes in Saga |
