Comparative Analysis of the Horizontal Positional Accuracy of Google Earth and Bing Imageries of Samaru, Kaduna State Nigeria

Abstract

Satellite imageries have in the recent past gained popularity in the areas of geo-informatics and geo-positioning because they provide global coverage and are cost-effective. Nevertheless, the use of these services poses questions on their spatial data quality in terms of positional reliability and accuracy, which have implications for their applicability. This study, therefore, analyzed the horizontal positional accuracy of satellite imageries (Google Earth and Bing) of Samaru in Kaduna state, Nigeria. The coordinates of 63 ground points (GPs) acquired with the Total Station instrument (Leica TCA 1201 M) were assessed against their corresponding points on the imageries using simple statistical accuracy metrics. The results revealed that the root mean square error (RMSE) of positions on the ground were significantly different from the RMSE of positions on the Google Earth and Bing imageries only in the Easting direction at the 95% significance level when p (2-tailed) = 0.000 [p < 0.05]. The study revealed that 50% and 70% of the Easting and Northing coordinates of the Google Earth imagery were related to the corresponding ground coordinates. In addition, 51% and 67% of the Easting and Northing coordinates of the Bing imagery were related to the corresponding ground coordinates. The results also showed that the Google Earth and Bing imageries had an overall positional accuracy of 6.09 m and 6.02 m, respectively, with the latter being more reliable in determining horizontal positions in the study area. The accuracy obtained was sufficient for navigation purposes and ground-based measurements that do not require very high accuracy. It was suggested, however, that a geometrical accuracy evaluation of similar or different imageries of the same study location or a more complex terrain should be undertaken to determine their reliability.