Step 1: List what each option means in one line. Resection: the instrument or receiver stands at the unknown point and looks outward at known points. Intersection: the instrument stands at known points and looks inward at the unknown point. Triangulateration: a control network technique blending angle, triangulation, and distance, trilateration, observations across many stations. Reduction: a computational correction applied to raw field observations, not a point fixing method.
Step 2: Eliminate options that describe the wrong observer location. In GNSS, the receiver on the ground, or on the object being positioned, does the observing, and it is exactly this receiver coordinates that are unknown. The satellites, whose coordinates are precisely known from the broadcast ephemeris, play the role of known control points. Since the unknown station, the receiver, is where the measurements are physically taken, this immediately rules out Intersection (B), which requires the observing instruments to sit at the known points instead.
Step 3: Eliminate the remaining wrong options. Triangulateration (C) describes a network wide combination of angles and distances across many interconnected known and unknown stations, a broader classical surveying network technique, not the geometric principle of a single point GNSS fix. Reduction (D) is not a positioning principle at all, it refers to adjusting or correcting measured quantities, so it cannot describe how a position is obtained in the first place.
Step 4: Confirm the surviving option. What remains is Resection: the GNSS receiver, standing at the unknown point, measures distances, ranges, hence trilateration as stated in the question, to multiple known satellite positions and resects its own coordinates. This is consistent with trilateration being described as the principle, since resection is the general geometric category and trilateration, distance based, is the specific technique used within it.
