| 摘要 |
<p>A method of forming an estimate of the two-dimensional position of a radio receiver relative to a plurality of radio transmitters each having an associated position estimate and a position uncertainty expressible as an uncertainty ellipse having major and minor axes, the method comprising: receiving at the radio receiver signals from the plurality of radio transmitters and forming in dependence on those received signals a set of transmitter weighting values each expressing a measure of the distance of a respective radio transmitter from the radio receiver; for each of the plurality of radio transmitters, scaling an uncertainty vector describing the orientation of the respective uncertainty ellipse in a predetermined coordinate system by a scaling value dependent on the respective transmitter weighting value and rotating that uncertainty vector by multiplying its argument by a factor of four; summing the scaled vectors of the plurality of radio transmitters so as to form a total vector; dividing the argument of the total vector by a factor of four and using the resulting rotated total vector to define a compound coordinate basis comprising first and second coordinate axes; and forming an estimate of the two-dimensional position of the radio receiver in the compound coordinate basis by: projecting the major and minor axes of each uncertainty ellipse onto the first and second coordinate axes so as to form a set of projected components for each axis; summing the projected components of each axis so as to form a total uncertainty along each axis; for each uncertainty ellipse, forming first and second coordinate axis weighting values from the respective transmitter weighting values scaled such that the first/second coordinate axis weighting value decreases as the total uncertainty along that first/second coordinate axis increases; and calculating the position of the radio receiver by means of a weighted centroid using the first and second coordinate axis weighting values and the position estimates of the plurality of the radio transmitters expressed in the compound coordinate basis.</p> |
