Comparative study of accuracy of differential global positioning system (DGPS) and total station instruments

Abstract

Total Station and Global Positioning System (GPS) are two instruments used to fix position on the earth. The total station employs electro-optical distance meter method, emitting laser beams to a target and detecting light reflected off it by measuring the deviation of the wavelength of the reflected light. Global Positioning System (GPS) is a space-based satellite for rapid position determination, its’ receiver calculates its position by precisely turning the signal sent by GPS satellite high above the earth. The study aims at the assessment of the two instruments: GPS and Total Station. To achieve this aim, two surveys were performed on the same parcel of land using the two instruments. In the first part of the survey, a closed-loop traverse was performed around a chosen parcel of land using a calibrated total station. The station determined only coordinates of points from where bearings and distances were extracted. Thereafter, DGPS equipment was then used to perform a similar survey as the total station. In this case, visible satellites were used to determine the coordinates of all the stations. The results of the two methods present the distances, bearings, and coordinates. The difference between each of the results was also analyzed. Thus the maximum average difference in distance of 5mm occurred throughout the chainage and maximum differences in the coordinate of 12mm Easting and 9mm Northing were found where there are tree covers. However, the study shows that even though the two instruments are good tools for positioning, each exhibited it’s own accuracy, efficiency, advantages and disadvantage.