HORIZONTAL POSITIONAL ACCURACY OF GOOGLE EARTH’S IMAGERY OVER RURAL AREAS: A STUDY CASE IN TAMAULIPAS, MEXICO

Resumo

Due to the popularity of Google Earth (GE), users commonly assume that it is a
credible and accurate source of information. Consequently, GE’s imagery is
frequently used in scientific and others projects. However, Google states that data
available in their geographic products are only approximations and, therefore, their
accuracy is not officially documented. In this paper, the horizontal positional
accuracy of GE’s imagery is assessed by means of comparing coordinates extracted
from a rural cadastral database against coordinates extracted from well-defined and
inferred check points in GE’s imagery. The results suggest that if a large number of
well-defined points are extracted from areas of high resolution imagery, GE’s
imagery over rural areas meets the horizontal accuracy requirements of the ASPRS
for the production of “Class 1” 1:20,000 maps. Nonetheless, the results also show
that georegistration and large horizontal errors occur in GE’s imagery.
Consequently, despite its overall horizontal positional accuracy, coordinates
extracted from GE’s imagery should be used with caution.