**1. Introduction**

Nearly of today the global navigation satellite system global positioning system (GNSS GPS) technology has been played as remarkable tool for positioning and mapping and with high accuracy can be achieved in the easiest way [1–3]. By observing several satellites and measuring their distance, and with the known of their satellite coordinates and the distance from observation, in this case the coordinate on location at the earth can be calculated. In everywhere and in anytime worldwide when signals from the satellites are received by the receivers, in these cases the position in 3D or even 4D can be determined precisely and even with

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precision in the order of millimeter. The GNSS (GPS) indeed become a revolution in positioning on the twentieth century.

Repeated or continuous monitoring of accurate positions on the objects (e.g., offshore oil and gas platform) may reveal the changing of positions which are representing deformation (e.g., subsidence). Due to oil and gas exploitation, offshore oil and gas platform may experience subsidence. The rates can vary from 1 to 10 cm per year and even more for certain places. This subsidence information is mandatory for risk assessment and safety requirement. Continuing subsidence may deform the platform infrastructures, adding the risk for any failure on the platform objects.
