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20051205: IDV - realtime track

>From: "Larry D. Oolman" <address@hidden>
>Organization: University of Wyoming
>Keywords: 200512051756.jB5HuN7s005531 IDV realtime tracks

Hi Larry-

>Does IDV support reading track files that are
>being generated realtime?  We are interested in
>being able to display data that is being telemetered
>from King Air aircraft during research projects.

Sorry for the delay in responding.  It turns out that
the auto update of tracks in 1.2 is broken.  I've fixed
that in the 1.3b1 release that I just made.

In general, certain types of data sources can be set up
to poll for changes.  The TrackDataSource is one of those.
The polling is just a file based polling on the update
times for the file.

To turn on the polling, you need a special chooser, or
override a property in the existing file chooser.  You can
do the latter by pasting the following xml into a
file called choosers.xml and placing that in your
~/.metapps/DefaultIdv directory.  The xml is:

<?xml version="1.0" encoding="UTF-8"?>
<choosers>
  <panel
     title="Files"
     layout="border"
     tabTooltip="For accessing local files"
     mnemonic="C">
    <chooser
       id="chooser.file"
       title="Files"
       menutitle="From the File System"
       showinmenu="true"
       helppath="idv.data.choosers.file"
       class="ucar.unidata.idv.chooser.FileChooser"
       showpolling="true"
       filters=".*\.xidv:IDV files (*.xidv);"/>
  </panel>
</choosers>

In this case, all I did was change the showpolling property
to true.  The effect will be a checkbox in the Files chooser
that you click if you want to poll on a particular file that
you've selected.

If you want this to be a separate tab, you can change
the id to be something like "chooser.pollingfile".  That
is the unique id for a chooser and if you don't change
it, it overrides the system version.

Once you've loaded in the file with polling turned on, you
can change the polling properties by right clicking on the
Data Source in the Field Selector and choosing the 
Properties menu.  Polling properties are under the
Properties tab (we'll put them in a separate tab in
a future release).  You can set the polling interval,
and turn polling on and off.

Again, you can also create a custom chooser, but that's
a little more work and would involve some code writing.

Give this a try and let me know if you have any questions
or problems.

Don Murray
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