Assessment of the Accuracy of Google Earth Imagery for use as a Tool in Accident Reconstruction

Google Earth is a map and geographical information application created and maintained by Google Corporation. The program displays maps of the Earth using images obtained from available satellite imagery, aerial photography and geographic information systems (GIS) 3D globe. Google Earth has become a tool often used by accident reconstructionists to create site drawings and obtain dimensional information. In some cases, a reconstructionist will not be able to inspect the site of the crash due to various circumstances. For example, a reconstruction may commence after the roadway on which the accident occurred has been modified. In other cases, the time and expense required to physically inspect the incident site is not justifiable. In these instances, a reconstructionist may have to rely on Google Earth imagery for dimensional information about the site. The accuracy of Google Earth is not officially documented. To provide a reconstructionist with an estimate of this accuracy, this paper compares measurements made using Google Earth imagery with measurements done by laser theodolite, and laser scanned measurements. Comparisons are made at sites in various states including rural and urban locations. The comparisons show that Google Earth images yield reasonably accurate measurements (RMSE 0.569 feet) over the scale of typical accident reconstruction distances.