Archive for November, 2009

GPS Satellite Outage Calendar – updates

November 19th, 2009 | Category: Utilities and Tools
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After looking at the sorry state of the GPS Satellite Calendar App, I decided to make some updates.  Ok, it wasn't that sorry, after all it did show all the GPS outages in calendar format.  But, once you're used to that, it gets boring.  So, I added a few features and I'll be adding more in the weeks to come.

New features

  • One thing I hated about the old calendar, is that to see the outages for February of this year, you had to click the << arrows multiple times to get to February.  Heaven help you if you wanted to see the outages from a previous year.  So, I added some drop down boxes that let you pick any month and year for which there is data - much easier!

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  • Next I added some tables below the Calendar, listing the Current or Predicted outages.  This gives you a quick look at what's currently out and what's predicted to be out.  Note that current outages are always in red in the calendar, and predicted outages are always in yellow.

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  • I also updated the text in some of the fields of the tables to link to the definitions for the outage types, or the NANU itself for a given outage.  All links are referenced to the Celestrak NANU web pages.
  • You can also click on the table column header to sort the outage data on that column.
  • The Historical listing of NANUs was ok, but it was just a big list of all NANUs published since 1998.  I updated that listing to be on a separate page, and have the same links and sorting capability.  I also added a column that lists the duration of the outage, defined by the NANU start and end times.  Click the Historical Outages link at the bottom of the page:

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and a new page or tab will open with the Historical outages table:

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Looking at the last three outages (at the bottom of the table), we can see that the SVs were only out for 5-7 hours:

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Which outage was the longest?, which was the shortest?  Sort on the Duration Column.

Which Satellite had the fewest number of outages?  Sort on the SVN or PRN column and see how many rows there are.

As I mentioned above, I'll be making some further updates in the coming weeks:

  • Some of you may have seen Richard Langley's article in the November 2009 issue of GPS World, about the GPS constellation being maxed out at 30.  For that article, I produced a picture of the number of healthy GPS satellites since 1998:

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I'll be updating this picture each time a new outage is posted, and placing it on the page as well.  This way we'll have a running tally of the outages and the number of healthy satellites in the constellation.

  • I'll also add some controls to the page that will allow you to explore outage information by PRN, time or PRN and time, as this sample application does.

If you have anything you'd like to see on this calendar, let me know, I'll see what I can do.

Happy navigating!

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