Satellite-based sensors enable frequent mapping and analysis of very large areas. Many sensing instruments are able to measure electromagnetic energy at multiple wavelengths, including those beyond the visible band. Satellite remote sensing is a key source for regional- and global-scale land use and land cover mapping, environmental resource management, mineral exploration, and global change research. Shipboard sensors employ acoustic energy to determine seafloor depth or to create imagery of the seafloor or water column. The topics included in this unit do not comprise an exhaustive treatment of remote sensing, but they are aspects of the field about which all geospatial professionals should be knowledgeable.