Temporal Resolution

Temporal resolution, well defined in the field of remote sensing, is one of four major resolutions that characterize a remote sensing system; the others are spectral, spatial, and radiometric resolutions. Temporal resolution is the length of time that has elapsed between measurements and captures the rate of data collection for a particular area. It can range from seconds to hours to days to years. Temporal resolution defines the minimum length of time over which an event can occur to be discernible in the database. For example, satellite images acquired for a forested landscape every year during the summer season will not capture phonological changes. Temporal resolution also plays an important role in geographic information science (GIScience) because all geographic data are defined with regard to spatial, temporal, and thematic dimensions.

In remote sensing, temporal resolution represents how often a remote sensing system records imagery for the same area. It is a measure of the length of time required for the sensor to pass over and return to exactly the same location, typically referred to as the revisit time. Remote sensing systems often differ with respect to temporal resolution. For example, Landsat 1 was able to acquire imagery of the same location every 18 days. Landsat 7 acquires imagery of the same location every 16 days. Therefore, Landsat 7 has greater temporal resolution. As the temporal resolution of a remote sensing sensor improves and the length of time between image acquisition declines, the number of images that can be acquired for the same area increases.

One of the most important aspects of a remote sensing system is its ability to collect imagery for the same location at multiple points in time. Comparing multitemporal imagery allows researchers to detect changes in spectral properties on the Earth's surface. Temporal resolution plays an important role in our ability to monitor these changes. For example, monitoring the growth of urban development would require a different temporal resolution (months to years) than monitoring the spread of a forest fire (hours to days). The temporal resolution of the remote sensing system should reflect the changes occurring in the phenomenon under investigation.

In geographic information systems (GIS), temporal resolution refers to the length of time between map updates. For practical reasons, data in a GIS are measured and recorded in discrete temporal units, where each data layer displays the spatial distribution of the variable of interest at one point in time. When a set of data layers are acquired for a variable of interest over the same area at several time steps, the length of the time step between the layers represents the temporal resolution of the GIS database.