Updated:  2009-nov-04

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Dilution of Precision (DOP) Animations:

A Note On The Animations

Fine Print Department -- The figure and the animations have a minor problem with the color bar legend. DOPs are unitless. DOPs are not units of meters. Please ignore the erroneous 'm' in the color bar legend. Sorry about that.

To View The Animations

You can use your favorite AVI player. I use Windows Media Player version 10. I split the animation into parts for ease of download. Try a part out to see if you like it, and to see if your AVI viewer will work with the contents.

Warning: AVI is a "container" format. There is another video format inside the AVI. The animations are MPEG-4 ASP video format. This is also known as XidD.

Fun Tip: If the AVI plays, and you have downloaded all the parts, then you can do a "drag-and-drop" onto the Windows Media Player window, and it will play the parts in sequence.

Windows Media Player

The "vanilla" version of Windows Media Player does not recognize the MPEG-4 ASP video format. It might issue an error message. If it does, it's because it wants a codec. It doesn't say this directly, but that's what it wants. You can find the open source XviD codec (XviD-1.1.3-28062007.exe) at:

with an FAQ at:

Install it, and then Media Player should be happy.

By the way, I don't use Vista. So, if you have a Vista problem, I can't help. Sorry.

What Is A "codec"?

Codec stands for compressor/decompressor. Think of it like an un-zip utility for video files. It will install in the Media Player's codec library, and be invoked on the fly whenever it is needed.

About The Figure

The figure depicts the 02:42:30 frame from the Horizontal Dilution Of Precision (HDOP) animation for July 20, 2007. The plot shows HDOP distribution for an "all satellites in view" solution with a 5 degree cutoff angle. The HDOP's were computed on a regular 3'x3' grid over 24-53N, 230-294E (581 rows, 1281 columns). The figure shows an HDOP excursion (a "DOP hole") of 2.58 just north of Lake Ontario. The curved boundaries of the HDOP zones are footprints of the GPS satellites.

To Contact Me

My e-mail user name is the first initial of my first name followed by all the letters of my last name (see above). My ISP is "comcast", and it is a "dot-net", not a "dot-com". Sorry for not spelling out my e-mail address, but I try to keep the spam-bots from fingering me. But, just so the spam-bots don't feel left out, they can always go to

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