Uncertain data are abundant in numerous spatiotemporal applications providing location-based services. This chapter will first review these applications and explain why uncertainty is inherent, sometimes even intended, in their underlying data. Then, we will address two classical spatial queries: range search and nearest neighbor retrieval. We will see that the presence of uncertainty requires extending the traditional definitions of both queries, and thus, also invalidates the conventional algorithms designed for precise databases. We will survey the existing the variations of both queries specifically formulated on uncertain data. Finally, the algorithms for efficiently processing these queries will also be discussed.