Thematic data consists of a set of related features that are included within a single data subset. In other words, data of a common theme is generally grouped and organized within a single file structure. Within a drafting or GIS program, thematic data are grouped within a single layer (e.g., geologic units, state boundaries, soil class, etc.). A thematic map is designed to convey information about a single topic or theme, such as national highway map or a geologic map. The Thematic Data
page will take you to a list of resources for digital thematic data.
Topographic data come in many digital forms and file formats. The Topographic Data
page will take you to a list of online digital resources and provide additional information on the range of available formats.
Finding spatially referenced data for individual states can be a challenge. The character and accessibility of online data varies enormously from state to state. Some states have a a central clearing house for all data; in other states, different types of data are housed on different sites. Our listing of data sources for individual states provides state-by-state links to all of the major online data sources for each state.
Remote sensing data consists of images that are constructed from data gathered without actual contact with the object being investigated. The most common example would be satellite imagery (Landsat, MODIS, GOES, ASTER, etc.). This type of data also includes aerial and satellite photography, seismic and ground penetrating radar data, multi-spectral LiDAR data, etc. The Remote Sensing
page provides links to key resources for acquiring a range of remotely sensed data.