Magnitudes of effects of ambiguities Basic changes in phase with ambiguities △LC f2/f1 4N,-198N MLG=-(2/f1)N1+N2=-0.78N+NM2 Notice that N1=N2=1(not detectable in the Mw Widelane)cause a change of 0.56 cycles in LC and only 0.22 cycles in LG (variations in LG can be several cycles) Combinations such as n1=3. n2=4 and n1=4 and n2=5 can cause small effects in LC (ie, geodetic fit looks good but ionospheric delay in error: if small can be detected but when large can be difficult) 12540Lec22 Cycle slip detection in kinematic processing Detecting cycles slips can be difficult in kinematic processing because of vehicle movement. Normally in static GPS, coordinates are well enough known that changes on phase(LC combination) between epochs of data can be used. If a change is larger an a tolerance level (usually 0.2 to 0.5 cycles) then a cycle slip is detected Cycle slips are resolved to integers to fitting with simply polynomials across the epoch with the jump In kinematic processing this is much more difficult because the position of the moving receiver is not† 05/07/03 12.540 Lec 22 11 Magnitudes of effects of ambiguities • • a change of 0.56 cycles in LC and only 0.22 cycles in LG (variations in LG can be several cycles) • Combinations such as N1=3, N2=4 and N1=4 and N2=5 can cause small effects in LC (ie., geodetic fit looks good but ionospheric delay in error: if small can be detected but when large can be difficult). DLC = 1 1 - ( f2 / f1) 2 N1 - f2 / f1 1- ( f2 / f1) 2 N2 = 2.54N1 -1.98N2 DLG ( f2 / f1)N1 + N2 0.78N1 + N2 Basic changes in phase with ambiguities Notice that N1=N2=1 (not detectable in the MW Widelane) cause = - = - 05/07/03 12.540 Lec 22 12 processing • Detecting cycles slips can be difficult in kinematic processing because of vehicle movement. Normally in static GPS, coordinates are well enough known that of data can be used. If a change is larger an a tolerance level (usually 0.2 to 0.5 cycles) then a cycle slip is detected. • Cycle slips are resolved to integers to fitting with • known. Cycle slip detection in kinematic changes on phase (LC combination) between epochs simply polynomials across the epoch with the jump. In kinematic processing this is much more difficult because the position of the moving receiver is not 6