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Comment by kubiiii | Hacker News Reader

It does, in fact GPS positioning error, derived from fixed GPS stations, is often used as an input for weather forecast models like WRF. The error is closely binded to the atmospheric water content. Using the different azimuths from the GPS constellation you can even build up a 3d representation of the water content on different layers of the atmosphere.

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This is possibly the most interesting thing I've read on HN. I knew that a similar principle is used for CT scans, but I never thought of blowing it up to Earth-scale. Thank you.

Thanks. This work is interesting http://tel.archives-ouvertes.fr/tel-00444081 Unfortunately the main thesis is in french, however there are included articles in english and lots of references. I am currently working on a project using a high density GPS stations network we deployed in the south east of France. We have had good results for nowcasting and to map in 3d the atmospheric weather content. No publication yet though.

2d maps of rainfall have also been derived from interpolated GSM antennas, using the signal loss.

I've done a ton of research into precision positioning with GPS (centimeter resolution). Have you investigated using NOAA CORS data in your project? http://geodesy.noaa.gov/CORS/

Disclaimer: GPS is one of those parts of science that gives me the nerd chills.

Cors data is limited to the USA, we used RGP data, a network of ground stations maintained by the IGN which is analogous to Cors. The IGS gathers data throughout the world to enable global applications but it looks like the data is more complete when accessed through national networks.

I worked a few years ago on precision guidance. I was supposed to assess the performance of automatically guided tractors. Sub centimetric guidance on 4 tons huge tractors was pretty tricky to test. On what exactly did you work?

You also have satellites with GPS receivers, so that they can measure the effects when the GPS signal skims the atmosphere. This allows humidity and temperature to be measured with very high accuracy, with a very good vertical resolution.

http://en.wikipedia.org/wiki/GNSS_radio_occultation

You're making a good distinction here. The research on using GPS occultation for sensing water vapor that I'm most familiar with uses two satellites, and does not use ground stations.

I am biased here, because I know the people who are developing this technology, so I'd be welcome to further information on this point! E.g., I took a look at the thesis abstract pointed to by @kubiii, but it wasn't specific enough to tell what their exact sensing method was.

There are some generally good-quality summaries of GPS radio occultation here: http://geooptics.com/?page_id=148

The main advantages of GPS occultation for H2O sensing are that it's relatively bias-free (compared to microwave radiometers), that it can see through clouds, and that it has better usable vertical resolution.

Yes, that's exactly it. Two satellites - one is a standard GPS satellite, and the other is a satellite with a GPS receiver.

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