An apparatus for determining a distance based on a transmitted signal, comprising: a signal processing circuit (101-102, 201-202) that receives, demodulates and digitizes the transmitted signal to provide digital demodulated samples of the transmitted signal; a storage device (104, 205) providing a first set of signal values representing time-ordered noise-less signal values of the transmitted signal, the first set of signal values being divided into sections, each section being associated according to a predetermined criterion with one of a plurality of categories, and each section having a predetermined number of signal values with each signal value being associated with a sample index representing a temporal position of the signal value in time; a signal interface (202/204) for receiving a second set of signal values representing the digital demodulated samples, each of the signal values in the second set of signal values being assigned a category and a sample index based on a predetermined alignment in time with the signal values of the first set of signal values, wherein each signal value in the second set of signal value is assigned the same category and sample index as the corresponding signal value in the first set of signal values to which the signal value in the second set of signal values is aligned; a set of accumulators (204, 1201-1209) each being associated with a corresponding one of the categories and a corresponding sample index, each accumulator being configured to sum a subset of signal values selected from the second set of signal values, the subset of signal values being signal values that are assigned to corresponding category and sample index; an arithmetic unit (204, 1210) configured to compute one or more cross-correlations of the transmitted signal and the received signal using the first set of signal values and the sums in the accumulators under one or more predetermined offsets in time relative to the predetermined alignment; and a CPU configured to calculate a distance based on the cross-correlations determined by the arithmetic unit (204, 1210). a signal processing circuit (101-102, 201-202) that receives, demodulates and digitizes the transmitted signal to provide digital demodulated samples of the transmitted signal; a storage device (104, 205) providing a first set of signal values representing time-ordered noise-less signal values of the transmitted signal, the first set of signal values being divided into sections, each section being associated according to a predetermined criterion with one of a plurality of categories, and each section having a predetermined number of signal values with each signal value being associated with a sample index representing a temporal position of the signal value in time; a signal interface (202/204) for receiving a second set of signal values representing the digital demodulated samples, each of the signal values in the second set of signal values being assigned a category and a sample index based on a predetermined alignment in time with the signal values of the first set of signal values, wherein each signal value in the second set of signal value is assigned the same category and sample index as the corresponding signal value in the first set of signal values to which the signal value in the second set of signal values is aligned; a set of accumulators (204, 1201-1209) each being associated with a corresponding one of the categories and a corresponding sample index, each accumulator being configured to sum a subset of signal values selected from the second set of signal values, the subset of signal values being signal values that are assigned to corresponding category and sample index; an arithmetic unit (204, 1210) configured to compute one or more cross-correlations of the transmitted signal and the received signal using the first set of signal values and the sums in the accumulators under one or more predetermined offsets in time relative to the predetermined alignment; and a CPU configured to calculate a distance based on the cross-correlations determined by the arithmetic unit (204, 1210).