3D ionospheric tomography using GEOTRIM GPS measurements


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Geotrim GPS stations

TEC measurement and inversion theory

Vertical el. dens. profiles

TEC along meridians

TEC and Ne statistics

The electron density through the 3-dimensional ionosphere can be estimated with help of TEC (Total Electron Content) measurements using multiple satellites and receivers, as illustrated in the figure above. This is done using an inversion procedure.

The inversion procedure looks for the electron density distribution as a function of 3D location and time, such that the integrated electron density along the path is equal to the measured TEC, for each path between any satellite and any receiver.

The accuracy of the result of the inversion increases with the number of available measurements on crossing paths. Hence, it is beneficial to use as many satellites and receivers as possible. In the case of Geotrim, the group of satellites are the GPS constellation, with currently 31 transmitting satellites, of which usually 8-10 are simultaneously visible at any given time, from most locations on earth. The receivers are the 86 receivers of the Geotrim network, distributed all over Finland.

At the moment, only data from December 2006 have been processed. Recent data are being continuously collected since March 2010, and the results should be coming soon.

Available results (quicklook plots)

More info



More information:
Max van de Kamp (tel. +358 9 1929 4687)
Olaf Amm (tel. +358 9 1929 4689)
Kirsti Kauristie (tel. +358 9 1929 4637)
e-mails: all.parts.of.the.name at fmi.fi