Thursday, January 26, 2006

L2C and GPS Satellites

Before everyone gets too excited about the announcements on L2C availability for GPS users (a new civilian signal) consider this first: there is one satellite capable of transmitting L2C signals, two more planned for 2006 and 12 for the next years. This satellite will be going around the Earth during its lifetime.

Two: Twenty Block II (plus 9 Block IIR, Replenishment) satellites rover around the Earth today, they are not geo-stationaries. They are only visible from a given location for some hours during the day. If you want to check when a satellite will be visible from your or any other area, check this Planning software from Trimble.

Three: you will need a dual or multi-frequency receiver capable of handling the currently available L1, (in some products L2) and the new L2C frequencies. So, it is great that these changes are coming, thanks to the recognition for the need of quality location data by groups like surveyors. But they will take a good couple of years to happen and for now they sound more like a PR effort from the White House to compensate the volume of press given to Galileo, the European Space Agency effort that will also take some years to be fully available.

L2C signals will be more powerful than the current L1 used by handheld GPS devices. Good news are that another even better signal called L5 will be made available in the future, with an even higher power level and larger bandwidth that will "make it even easier to acquire and track weak signals". The first satellite carrying L5 capable payload should be launched sometime this year.

Trimble seems to be the only vendor that currently offers, thanks to its proximity to the group that developed the new payload of the new satelittes, receivers capable of handling L2C (and L5) signals.

Finally, it may take a while for mass market production of consumer oriented chipsets capable of handling multi-frequency signals that can feed consumers with cool gadgets. Surveyors, planes and boats will come first. Probably in this order. Geocaching will most possibly come after them.

Check this article from Professional Surveyor Magazine and this one from Trimble for a good history and the current state of the GPS Satellites.

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