Authors: Salar Khudhur Hussein1 & Kamal Yaseen Abdulla2
1Civil Engineering Department, Technical College, Erbil Polytechnic University, Erbil, Iraq
2Civil Engineering Department, Technical College, Erbil Polytechnic University, Erbil, Iraq
Abstract: Today, advanced Global Navigation Satellite System (GNSS) receivers are improving the accuracy of positioning information, but in critical locations such as urban areas, places with big trees, high tension electric poles, marshes, high buildings, mountainous areas, and so on, the satellite availability is limited due to the signal blocking problem, which degrade the required accuracy. For this reason, different methods of measurement should be used.
The objective of this study is to evaluate and compare the precision, the accuracy, and the time expenditure of total station (TS), Global Positioning System (GPS), currently called (GNSS), (Static and Real Time Kinematic methods). Measurements will improve the knowledge about how much precision and accuracy can be achieved and at what time expense. To investigate this task, two Benchmarks (BMs) were established inside the campus of College of Technology Erbil polytechnic University (EPU) which are used as base lines for the establishment of a reference network consisted of 20 control points. Each point was measured five times by using Topcon 105 Total Station and served as a reference value for comparison with RTK-GNSS, GPS instrument. The data were processed from the instruments to a computer using different software according to the instruments used such as Topcon Tools v7, Trimble’s GNSS Net, GIS Map Source Version 6.4, and Leica geo office software.
The registration and geo-referencing (using Arc Map 10.2.2. software) process was performed to convert the scanned satellite images of the point cloud to combine scanned maps together in one coordinate system then transformed to World Geodetic System 1984 (WGS84).
According to the obtained results, the reference network points measured with TS were determined with Easting13mm, Northing 11mm and Elevation 15mm precisions for both horizontal and vertical coordinates. When using RTK-GNSS method on the same reference network points, which is expressed by RMSE, the accuracy obtained for easting was 8 mm, for northing was 10.6mm, and 8.4 mm in elevation has been achieved. The RTK-GNSS measurements, which were measured five times, determined with a maximum standard deviation of Easting 0.9 mm, Northing 0.96 mm and Elevation 0.93 mm for horizontal and vertical coordinates, respectively. The precision of the remaining control points is below these levels.
The Center line of the road (120m) was projected (set out) using TS, then the points were measured with RTK-GNSS. The maximum difference between both methods in Easting was 19mm, in the Northing was 22 mm and in the Elevation was 30 mm. So, the differences considered to be small as it was in acceptable range.
Keywords: Global Navigation Satellite System (GNSS), Total Station (TS), Accuracy, Precision, GIS
Anzlic (Australia and New Zealand Land Information Council), (2006). Glossary: spatial information related terms. Retrieved on March 23, (2013) from https://anzlic.org.au/glossary_terms.html.
Chekole, S. D. (2014). Surveying with GNSS, TS and terresterial laser scaner: A comparative study NO.3131, school of architecture and the built environment. Journal, Royal Institute of Technology (KTH), Stockholm, Sweden (published)
Dawod, G., & Alnaggar, D. (2000). Optimum geodetic datum transformation techniques for GNSS surveys in Egypt. Proceedings of Al-Azhar Engineering .
Geocart, (2012). Bench Marke(BM) array arbile documention of fixed point (FP) location fixed point within the geodetic benchmark (FP–24) array Germany, 2012-06-29.
Jonsson, K.O., Andersson, A., Jacobsson, S.O., Vandevoorde, S., Lambert, D.M., & Fowler, C.J. (2003). SWEPOS Network-RTK Services, status, applications and experiences. Presented at GNSS/GNSS 2003, 9-12 September 2003, Portland, Oregon, U.S.A.
Kavanagh, B. F (2011). Surveying with construction applications. Pearson. Seventh Edition. Ch-7, pp.198-222
Kostov, G. (2011). Using of both fast Static and RTK-GNSS Modes for GNSS determination to obtain required high accuracy and productivity, according to the current possibilities of the IT Marrakech, Morocco.
Surveying, Britannica online, retrieved on 09 February, (2013), from https://britannica.com/EBchecked/topic/575433/surveying
Topcon, (2007). Instruction manual easy ES105 series Total Station instrument topcon (JSIMA)Japan surveying Instruments manufacturers Association .
Walser, B. (2005). Development and calibration of an image assisted TS. Mitteilungen. second Edition. Ch-2,pp.198-222
Yenter, C. M. W., Wheeier, L. T. A., Mejia, M. C., & Stoughton, H. W. ( 2005). Development of the Iraqi Geospatial Reference System.
Zhang, K., Wu, F., Wu, S., Rizos, C., Lim, S., Roberts, C., Ge, L., & Kealy, A. (2007). The latest development of a state-wide GNSS network-based RTK system in Australia. In Proceedings of IONGNSS.