A geodetic control network is the wire-frame or the skeleton on which continuous and
consistent mapping, Geographic Information Systems (GIS), and surveys are based. Traditionally,
geodetic control points are established as permanent physical monuments placed in the ground and
precisely marked, located, and documented. With the development of satellite surveying methods
and their availability and high degree of accuracy, a geodetic control network could be established
by using GNSS and referred to an international terrestrial reference frame used as a threedimensional geocentric reference system for a country. Based on this concept, in 1992, the Egypt
Survey Authority (ESA) established two networks, namely High Accuracy Reference Network
(HARN) and the National Agricultural Cadastral Network (NACN). To transfer the International
Terrestrial Reference Frame to the HARN, the HARN was connected with four IGS stations. The
processing results were 1:10,000,000 (Order A) for HARN and 1:1,000,000 (Order B) for NACN
relative network accuracy standard between stations defined in ITRF1994 Epoch1996. Since
1996, ESA did not perform any updating or maintaining works for these networks.
To see how non-performing maintenance degrading the values of the HARN and NACN, the
available HARN and NACN stations in the Nile Delta were observed. The Processing of the tested
part was done by CSRS-PPP Service based on utilizing Precise Point Positioning ‘‘PPP’’ and Trimble Business Center ‘‘TBC’’. The study shows the feasibility of Precise Point Positioning in updating
the absolute positioning of the HARN network and its role in updating the reference frame (ITRF).
The study also confirmed the necessity of the absent role of datum maintenance of Egypt networks.
2016 Production and hosting by Elsevier B.V. on behalf of National Research Institute of Astronomy
and Geophysics. |
