3-3-5
The equations applied were:
e 0 = hrtk, 0 — h t rue, 0
Equation 1
p — h — h
c 'n n 'rtk,n "'true,n
Equation 2
h , = h cbs~ e ,
Equation 3
where,
hi is the corrected height at i th observation
h 0 bs is the observed height
ei is the error term (error correction to be
applied)
ei is given by:
correction
C: — e n +
e„ —e,
d.
*d ;
Equation 4
Where,
• e 0 is the error between the RTK Height
and the True value at Calibration Point
1
• e n is the error between the RTK Height
and the True Value at Calibration Point
2
RTK Height
Standard
Deviation
RMS Error
Before
Correction
7cm ~ 12cm
8cm ~30cm
After
Correction
1cm ~ 3cm
2cm ~ 4cm
Table 1: Comparison of Accuracy
• di is the distance from the calibration
point 1, to the point where the error is
to be applied
• d n is the total distance between the two
calibration points, Pier 1 and Pier 31
Figure 10 shows the results before and
after applying the error correction
equations. The accuracy thus improved is
listed in Table 1.
5. CONCLUSIONS
• Based on the above results and
analysis, it can be concluded that the
height accuracy can be improved to 2-
4cm (RMS) for a base length of three
kilometers. This is achieved by
applying the error correction to the data
observed in RTK mode.
• A GPS base station has been
established at Asian Institute of
Technology (AIT), Thailand, using
mobile phone for real time differential
correction.
• It was found that there was no effect of
antenna velocity on accuracy. Thus the