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For those who may not be aware, GPS signals can be used to measure atmospheric properties. As GRACE (or any satellite with a modern GPS receiver) listens to a GPS satellite that's about to pass below the horizon, the GPS signal passes through the atmosphere. Thus the GPS signal is refracted and delayed in ways that can reveal the temperature, pressure, and refractivity of the atmosphere at different altitudes. These are known as GPS occultation measurements.

I've never used GPS occultation measurements, so I asked Gerhard Kruizinga about them at the weekly GRACE meeting. He pointed me to GFZ which has near-real time data (that page shows GPS occultation measurements taken today, but getting the data from GFZ probably requires filling out a quick form). Gerhard also mentioned that GPS occultation measurements from GRACE are regularly fed into the ECMWF atmosphere model, which is briefly described here.

For those who may not be aware, GPS signals can be used to measure atmospheric properties. As GRACE (or any satellite with a modern GPS receiver) listens to a GPS satellite that's about to pass below the horizon, the GPS signal passes through the atmosphere. Thus the GPS signal is refracted and delayed in ways that can reveal the temperature, pressure, and refractivity of the atmosphere at different altitudes. These are known as GPS occultation measurements.

I've never used GPS occultation measurements, so I asked Gerhard Kruizinga about them at the weekly GRACE meeting. He pointed me to GFZ which has near-real time data (that page shows GPS occultation measurements taken today, but getting the data from GFZ probably requires filling out a quick form). Gerhard also mentioned that GPS occultation measurements from GRACE are regularly fed into the ECMWF atmosphere model, which is briefly described here.

For those who may not be aware, GPS signals can be used to measure atmospheric properties. As GRACE (or any satellite with a modern GPS receiver) listens to a GPS satellite that's about to pass below the horizon, the GPS signal passes through the atmosphere. Thus the GPS signal is refracted and delayed in ways that can reveal the temperature, pressure, and refractivity of the atmosphere at different altitudes. These are known as GPS occultation measurements.

I've never used GPS occultation measurements, so I asked Gerhard Kruizinga about them at the weekly GRACE meeting. He pointed me to GFZ which has near-real time data (that page shows GPS occultation measurements taken today, but getting the data from GFZ probably requires filling out a quick form). Gerhard also mentioned that GPS occultation measurements from GRACE are regularly fed into the ECMWF atmosphere model, which is briefly described here.

Yes, GRACE gravity measurements can be inverted to show that sea level behaves exactly as you describe. But since it defines sea level, the gp was accurate too. :)

You see, that's why slingbox and a portable satellite internet receiver would be a much better solution. If those receivers detected where you were and guaranteed that you would have national network service when you didn't have local service, and guaranteed that you would have local service in any city where local channels were available, it might not be so offensive, but with it cutting off access to your network channels outside your home area, that's just asking to be cracked.

I'd probably start with GPS simulation software if I were doing it, but if the device doesn't use GPS for a time reference, you might even get away with just using a software radio transceiver to do a simple replay attack of the GPS band and cable it up in place of the device's GPS antenna....

Until now the greatest seismic event detected by the SAS was the September 14, 1995, M7.3 "Copala" earthquake. In a live test that checked the whole system, the SAS was activated and a general warning signal was issued in Mexico City, 72 sec. prior to the arrival of strong ground motion effects.

Well not with US-Style advertising but working.
Based on a System used by GEOMAR before 2004.

http://www.ifm-geomar.de/index.php?id=2566&L=1
http://www.gfz-potsdam.de/html/projects/TEWS/index -en.html

The US Southern Calfornia Earthquake Center has had several versions in place (also) since the late 1980s. Oil company refineries, L.A. Metro Rail, and gas utility companies are among important customers.

Of course the early version had some snafus in the 1994 Northridge quake. At that time it was pager-based and pager buffer overflowed with lesser aftershocks. They fixed it up in time to successfully warn construction crews repairing freeway overpasses.

Mexico has been working on this equally long. They can experience magnitude eight quakes off its western shores. But by the time these seismic waves reach Mexico City several minutes later, they're peak energy is just that to resonate skyscapers which were built in the old Aztec lake bed. Early years there were a number of false alarms, but some successes too. As with Japan and the US, the current systems are more robust.

I've got a plotter at work (HP755CM), fed by non-general-purpose commercial software (Cadence Raptor), but I'd love to have a general-purpose Postscript->optimized-RTL path for it without having to touch Windows.

A quick Google search shows there are folks using Ghostscript "uniprint" drivers for DesignJets, and there is ppm2rtl, which looks pretty interesting.

-Jay-

One satellite that was launched and is busy producing data, is CHAMP. It too is mapping the Earth's gravity field, by virtue of GPS tracking and a three-axes accelerometer. And it is sounding the atmosphere by GPS limb sounding, just like GRACE will do and METSAT has been doing some time ago already.

For those not aware of the importance of GPS limb sounding, it is a method to determine indirectly the scale height and thus temperature around the tropopause, a useful indicator for global warming.

Actually one thing nobody here has pointed out is that GRACE aims at studying changes in the gravity field, mostly due to movements of ocean water, ground water, ice, air etc. etc. (in short, the 'blue film' we see in space photographs of Earth!). The sensitivity of the GRACE mission, which will consist of a satellite pair tracking each other, to such changes is quite unbelievable.

Try the CHAMP satellite site and the CHAMP Systems page has a link to the GPS system. The reflected GPS signals are used for additional GPS altitude info.

Try the CHAMP satellite site and the CHAMP Systems page has a link to the GPS system. The reflected GPS signals are used for additional GPS altitude info.