Float RTK (Real-Time Kinematic) is an intermediate GNSS positioning state where the receiver processes carrier phase measurements and applies differential corrections, but has not yet achieved integer ambiguity resolution. In this mode, the carrier phase ambiguities are estimated as floating-point (real) numbers rather than being constrained to their correct integer values, resulting in positioning accuracy typically in the decimeter to sub-meter range, significantly better than standalone GNSS but less precise than the centimeter-level accuracy achievable with fixed RTK.
Understanding float RTK requires familiarity with the carrier phase ambiguity problem. While carrier phase measurements provide millimeter-level ranging precision, each measurement contains an unknown integer number of complete carrier wavelengths between the satellite and receiver antenna. The ambiguity resolution process determines these integers, and success depends on adequate satellite geometry, sufficient observation time, strong signal quality, and appropriate baseline length. When conditions prevent reliable integer determination, the receiver maintains a float solution where ambiguities are estimated as continuous real numbers.
Float RTK commonly occurs during several scenarios: immediately after receiver startup while the ambiguity resolution algorithm accumulates observations; during brief signal obstructions that don’t fully reset the solution; in challenging environments with multipath or poor satellite geometry; and when baseline distances exceed the effective range of the correction source. The float solution represents a valid statistical estimate of position and may converge toward centimeter accuracy with time, but lacks the reliability and precision of a properly validated fixed solution.
For many applications, float RTK provides adequate accuracy. Navigation, general mapping, and reconnaissance surveying may tolerate decimeter-level uncertainty. However, applications demanding centimeter precision, control surveys, machine guidance, autonomous vehicles, and construction stakeout, require fixed RTK solutions. Modern receivers clearly indicate float versus fixed status, and professional workflows incorporate checks to ensure data is collected only when appropriate solution quality is achieved.
