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Use GPS to probe the ionosphere in real time?
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by AB5XZ on May 27, 2010
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My son is a scientist, not a DXer. Last week, however, he suggested to me that DXers could use GPS to monitor the ionosphere in real time. How, I said?
As I understood him, the ionosphere is the biggest contributor to GPS positioning error. A beacon station could monitor its positional error and the satellites visible at each measurement, and come up with a measurement of the ionosphere's electron density horizon-to-horizon. I read up on it a bit today and found that many countries have something equivalent to WAAS (Wide Area Augmentation System) that the US Federal Aviation Administration uses to take out the error introduced as the GPS signals pass through the ionosphere.
I don't know how easy it is to access the WAAS information or the similar information of other countries, but it seems like something to investigate. I would like to see the IARU beacons transmit their local GPS error every hour or so, for example. What do you contesters think? Would accurate real-time MUF data be of use in a contest?
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RE: Use GPS to probe the ionosphere in real time?
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by K8GU on June 3, 2010
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WAAS provides a gridded correction over the continental US and a few other US possessions. However, that may not be particularly useful for hams, even if you included international systems like EGNOS.
Something more useful would be so-called "TEC maps" which are produced from the same type of dual-frequency GPS receivers used to produce the WAAS corrections. The data from these receivers are fit to a model that gives a worldwide estimate of the vertical total electron content (VTEC), which is, in a loose sense, proportional to foF2 and the MUF. Here is an example of such a map that is updated every five minutes:
http://iono.jpl.nasa.gov/latest_rti_global.html
I believe that VE3NEA has been importing TEC map (perhaps GIM from CODE) information for his DX Atlas software for some time now, but I might be mistaken.
http://aiuws.unibe.ch/ionosphere/index.html
The GAIM model that is referenced on the JPL ionosphere group's home page is a more sophisticated model that ingests not only GPS data, but also data from many other instruments, to produce a 4-dimensional ionosphere model. GAIM and it's relatives can be ray-traced to provide very accurate propagation predictions. To my knowledge, this model and related assimilative models are only available to researchers and their sponsors at this time.
This work is being done. However, it's not widely known or accessible in the amateur community.
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