|
|
|
Mapping From Space
|
Accuracy Assessment an Improvement for Level Survey Survey using Real Time Kinematic (RTK) GPS
Figure 10 shows the results before and after applying the error correction equations. The accuracy thus improved is listed in table 1.
| | RTK Height |
| Standard Deviation | RMS Error |
| Before Correction | 7cm~12cm | 8cm~30cm |
| After Correction | 1cm~3cm | 2cm~4cm |
Table 1: comparison of Accuracy
Figure 10
Conclusions
Based on the above results and analysis, it can be concluded that the height accuracy can b e improved to 2-4 cm (RMS) for a base length of three kilometers. This sis achieved by applying the error correction to the data observed in RTK mode.
A GPS base station has been established as Asian Institute of Technology (AIT), Thailand, using mobile phone for real time differential correction .
It was found that was no effect of antenna velocity on accuracy. Thus the vehicle can be driven at any speed from 10km/hr without losing accuracy.
Minimum observation time required to achieve 20 cm precision as a function of base length as identified.
Recommendations
The applicability of this methodology has to be tested for different applications like mobile mapping, hydrological modeling and road affect area assessment etc.
There are still potholes where this methodology could be improved. The methodology has to be tested for different road conditions in urban environment, different topography of the road and longer calibration distance. Those could be further areas of research.
Figure 11. Survey Vehicle with Antenna on top.
Figure 12. The Overhead Crossing chose for Survey
References
- Cannon, M.E. and Lanhapell, G. (1992) Analysis of a high performance C/A code GPS Receiver in Kinematic mode , NAVIGATION, journal of the insitiute of Navigation vol .39 No. 3, USA
-
Chong , A.K. and Dewhirst , K. (1996) Calling GPS; Long -Range Positioning via Cellular Technology Sketch Technical Sketch .P50-53 .
-
Falkenberg, B., Ford, T., Neumann, J., Fenton, P., Cannon, M.E. and Lachapell, G. (1992) Precise Real Time Differential GPS using a cellular Radio Modem IEEE, PLANS Canada.
-
Geomantics Canada , Geodetic Survey Division , Accuracy Standards for Positioning .
-
Leick , A., (1995) GPS Satellite Surveying , second Edition, A Wiley-International Publication, 1995.
-
Seeber, G., 1993 , Satellite Geodesy, Foundations, Methods and Applications, Berlin, Walter de Gruyter.
-
Wu, J. and Lin, S.G., (1995) Height Accuracy of one and Half Centimeters by GPS Rapid Static Surveying , Int. J Remote, vol. 16, No. 15, 2863-2874.
|
|
|
|
|
|
|
