Today, there are large amounts of geospatial data available on the web such as Google Map (GM), OpenStreetMap (OSM), Flickr service, Wikimapia and others. All of these services called open source geospatial data. Geospatial data from different sources often has variable accuracy due to different data collection methods; therefore data accuracy may not meet the user requirement in varying organization. This paper aims to develop a tool to assess the quality of GM data by comparing it with formal data such as spatial data from Mayoralty of Baghdad (MB). This tool developed by Visual Basic language, and validated on two different study areas in Baghdad / Iraq (Al-Karada and Al- Kadhumiyah). The positional accuracy was assessed by adopting National Standard for Spatial Data Accuracy (NSSDA). The evaluation procedure also involved one and two-sample t-test to analyze and compare the accuracy of two study areas. The findings found that the NSSDA accuracy of case study one was 15.48 m, while it was 8.71 m for case study two. This indicated that the accuracy of the GM data is different from site to site. The results also showed that the difference on mean was 6.16 m, which indicated that there is a difference in GM accuracy in different areas. It was concluded that the GM data is inappropriate for engineering applications that require high accuracy, but may be appropriate for applications that need low accuracy such as the primarily surveying of engineering design projects, tourism and reconnaissance….etc.
