Managing/Repatriating Area-Specific Data Collection from the World Ocean Database
international collection of marine datasets, collectively named the World
Ocean Database (WOD), is accessed, and several principal data types are
downloaded (ocean station data, CTD data, mechanical bathythermograph data
and expendable bathythermograph data) from the 11 available types.
These data cover the entire historical period of record, and an area
slightly larger than the project area for Liberia, and will be used in
subsequent exercises with the Ocean Data View software.
Preliminary Reading (in
OceanTeacher, unless otherwise indicated):
|1. Open the WODSelect
interface. This is the
interface to select the various optional ways the global data can be
For this exercise, check GEOGRAPHIC COORDINATES, and DATASET;
if you have any special interests in how the data are selected, then you can
add other items, now or in a later run.
The OBSERVATION DATES item can also be checked, as discussed in a
|2. Near the
bottom of the list of criteria are two new items we need to think about:
- DATA EXCLUSION USING WOD QUALITY CONTROL FLAGS. We recommend that you do
not use this criterion
now, because you can also do it later in Ocean Data View.
- DATA ADDITIONS. "If you select this option you can
include only new data added between given dates. This could be useful
for someone who already has a collection and wants to update." [Greg
Reed] We recommend that you do not
use this criterion until you have become much more familiar with ODV and
have perhaps made some experiments to see how this filter really works.
|3. Now click BUILD A QUERY
|4. WODSelect has created a
query form based on GEOGRAPHIC COORDINATES and DATASET type (the
fields you selected above).
In the GEOGRAPHIC section, enter
coordinates that are 1 degree larger than the area-of-interest polygon.
This gives you a margin of data around the Liberia area to avoid "edge
effects" in calculations
5. In the dataset section, check these items (or more, or
fewer...up to you). Then
click GET AN INVENTORY.
|6. This inventory appears,
indicating that nearly 17,000 station are available (for OSD).
- If you get (below) an inventory that would be too large for you,
based on local Internet conditions, then go back and use the OBSERVATION
DATES to reduce the time period.
- The related
Metadata Exercise investigates the
CRUISE LIST, but we will ignore it now
Click VIEW DATA DISTRIBUTION PLOT.
|7. Here are all the data we
specified, for Liberia. Notice the heavy concentration of nearshore
stations (which is typical), and also the long north-south survey lines --
probably taken during some sort of special project.
Click on DOWNLOAD DATA.
|8. Set up the data download
as you see here:
- WOD NATIVE ASCII FORMAT - required by Ocean Data View software;
- DATA IN
SEPARATE FILES - Never combine different data types in the same download
- OBSERVED LEVEL DATA - The original measurements; standard level data
would only be estimates
- CHOOSE XMT/MBT CORRECTIONS - You can study this issue on your own later. It has to do with how fast the
probes fall through the water, and how depths are estimated from fall-times.
Unless you have a personal preference, just leave it at NO CORRECTIONS for
- The 2 options on the right
side, "COMMA DELIMITED VALUE" and "NETCDF FORMAT" are not needed in this
exercise, so they are ignored and not shown
|9. Enter your email address
(one that you can use this very day), and click EXTRACT DATA
|10. This status message tells
you that your data are being prepared for FTP transfer.
|11. Within a few minutes,
you'll receive an email like this. Right-click on the FTP link and
select SAVE AS.
12. What to do with the data?
- Save the OSD file in DATA > OCEAN > WOD > OSD with the filename
Do NOT unzip this file. It will be used by the Ocean Data View
software in zipped form.
- Similarly, save the other CTD and PFL files into their separate
similar folders, with the automatic filenames provided by WODselect.
- But, because they are so similar in content, you might save the MBT
and XBT data into a single folder named XBTMBT.
|13. Do NOT unzip
these files. They will be used by the Ocean Data View software in
14. For data security, you can optionally rename these files (or make
copies) with these filenames (changing the date, to today's date):
- ocldb1424265618.9272.OSD.gz --> osd_20150218_liberia_wod.gz
- ocldb1424265618.9272.CTD.gz --> ctd_20150218_liberia_wod.gz
- ocldb1424265618.9272.XBT.gz --> xbt_20150218_liberia_wod.gz
- ocldb1424265618.9272.MBT.gz --> mbt_20150218_liberia_wod.gz
- ocldb1424265618.9272.PFL.gz --> pfl_20150218_liberia_wod.gz
Both names are perfectly
acceptable, and you may encounter either or both in the ODV exercises.
- Legacy file from August 10, 2010, in
case you can't use WODSelect today. From an older WOD version, but suitable for