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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/11816

Authors: Mohamed Abd-Elazeem, Ashraf Farah,
Farrag A. Farrag
Keywords: Elevation angle – GPS positioning - Accuracy
Issue Date: 2010
Publisher: Faculty of Engineering- Al-Azhar University
Citation: Al-Azhar University Engineering Journal, JAUES, Vol. 5, No.1, Dec. 2010Pages: 565 -570
Abstract: GPS Technology proved its strength in different applications in various areas such as industry, agriculture, mapping, Geographical Information System (GIS) data collection, public safety, surveying, telecommunications, military, and transportation due to accessibility of Global Positioning System (GPS) signals. There are several satellites geometry factors must be considered when planning a GPS survey. These factors include the number of available satellites, elevation mask angle, distribution of satellites in the sky with respect to the receiver and DOP values. These factors affect on the geometry of the satellites in space at the time of observations and hence on GPS positioning accuracy. GPS positioning accuracy is a function of Geometric Dilution of Precision (GDOP) and ranging errors referred to as the user equivalent range error (UERE). Ranging errors contain the sources of errors which corrupting the code and carrier measurements. They are mainly: ionosphere delay, troposphere delay, clock errors, ephemeris errors, receiver noise, and multipath. Ranging error can be categorized in two types; satellite geometry dependant and independent. Satellite ephemeris and receiver noise are independent of satellite geometry. Ionospheric delay, tropospheric delay and multipath are based on satellite geometry especially on elevation angle. This paper aims to study the effect of elevation angle (E) on GPS positioning accuracy thus assess and modeling the performance of GPS technology in semi-urban areas. A center line of road was observed by using two techniques: stop and go GPS surveying and total station surveying. Different values of elevation angle were adopted during the processing of GPS observations ranging from 5 degree to 30 degree then the obtained coordinates were compared with total station coordinates. The results reveal that, the low elevation angles (10, 15 and 20 deg.) provide small differences between GPS and total station coordinates about 5.8 cm as 3D standard deviation comparing to high angles (25 and 30 deg.) which cause differences about 19.2 cm as 3D standard deviation. Therefore, the results prove that the best suitable value for elevation angle is (10-20 degree).
URI: http://hdl.handle.net/123456789/11816
Appears in Collections:College of Engineering

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