Wiki Testing/OpeNDAPQuickStartApril09

From OPeNDAP Documentation

[<ahref="/index.php?title=QuickStart&action=edit&section=5"title="Edit section: Sequence Data">edit</a>] Sequence Data

Note: We're currently updating our documentation. The information in this section references old demonstration servers we used to host at the University of Rhode Island which are no longer running. Please

bear with us while we update this Guide. Thanks. 10/31/08

Gridded data works well for satellite images, model data, and data compilations such as the Reynolds data we've just looked at. Other data, such as data measured at a specific site, is not so readily stored in that form. OPeNDAP provides a data type called a Sequence to store this kind of data.


A Sequence can be thought of as a relational data table, with each column representing a different data value, and each row representing a different data "instance." For example, an ocean {temperature profile} can be stored as a Sequence of pressure and temperature pairs, and a weather station's data can be stored as a Sequence with time in one column, and each weather variable occupying another column.

Let's look at a set of two Sequences. The first gives the locations of a set of inverted echo sounders, and the second gives their observations over time. The data is here:

http://dods.gso.uri.edu/cgi-bin/nph-dods/dods/ies/iess/ies_locations.dat

http://dods.gso.uri.edu/cgi-bin/nph-dods/dods/ies/iess/iess.dat

First, let's take a look at the data structure by appending .das to the URLs for the data, like this:

http://dods.gso.uri.edu/cgi-bin/nph-dods/dods/ies/ies_locations.dat.das

http://dods.gso.uri.edu/cgi-bin/nph-dods/dods/ies/iess.dat.das

The results look like this:

caption=../ies/ies_locations.dat.das

and like this:

caption=..//ies/iess.dat.das


We can get more information by looking at the DDS:

http://dods.gso.uri.edu/cgi-bin/nph-dods/dods/ies/ies_locations.dat.dds

Iess location dds.png

http://dods.gso.uri.edu/cgi-bin/nph-dods/dods/ies/iess.dat.dds

Iess dat dds.png


Now let's take a look at the actual data:

http://dods.gso.uri.edu/cgi-bin/nph-dods/dods/ies/iess.dat.asc

Iess dat asc.png


We see that some sampling locations didn't produce interesting data right away. So let's restrict our query to the last few sampling locations, by adding a constraint to the URL:

../dods/ies/iess.dat.asc?data_in.dyear,data_in.day,data_in.AET_inst08,data_in.AET_inst09,data_in.AET_inst10