Journal of Remote Sensing & GIS

A Short Note on Satellites and Temporal Resolution

Matthew Quincey^* Department of Geography and Earth Sciences, Jonas Campus, Aberystwyth University, Aberystwyth, UK
^*Correspondence: Matthew Quincey, Department of Geography and Earth Sciences, Jonas Campus, Aberystwyth University, Aberystwyth, UK, Email:

Received: 03-Jan-2022, Manuscript No. JGRS-22-211; Editor assigned: 05-Jan-2022, Pre QC No. JGRS-22-211; Reviewed: 19-Jan-2022, QC No. JGRS-22-211; Revised: 24-Jan-2022, Manuscript No. JGRS-22-211; Published: 31-Mar-2022, DOI: 10.35248/ 2469-4134/22.11.211

Description

Temporal resolution described by the image data acquired by remote sensing sensors. The temporal resolution plays an important role in providing information on the distance of time between the acquisitions of two images of the same area. The higher the temporal resolution, the shorter the distance of time between the acquisitions of images. Many satellites have a medial temporal resolution of about 14 days. But there are also some satellites with a very high temporal resolution capable of capturing photos of the same area every 15 minutes. Based on this reason satellite sensors with a high temporal resolution such as weather satellites are geostationary satellite sensors. Geostationary satellite systems are varied from the so called polar orbiting satellites in that they do not orbit and acquire images of the whole globe. Instead, they keenly observe the same portion of the surface of the Earth while staying in the same place. That way, they can obtain images of the same area at short mean time. As seen from earth, geostationary satellites abide in the same place as they move along to maintain parallel position to the earth. In order to collect more images with high quality, geostationary satellites flew even more high as approx. 36.000 km. In accordance, they have a lower spatial resolution than polar orbiting satellite systems.

Polar orbiting satellite systems can reach upto a certain height of approx. 900 km and thus have a higher spatial resolution than geostationary satellites. They spot a very small section of the surface of the earth, they fly from pole to pole following a very lopsided path while the earth keeps turning below them. In that way, they can acquire images of the whole surface of the earth in just two days. In some cases, usage of geostationary satellite images helpful. However, if we need images with a high spatial resolution for creating a map of a certain area, one should use images of a polar orbiting satellite.

Satellite information with a high temporal resolution can be used in order to observe phenomena such as the tide. The tidal forces affecting on the earth are caused by the gravitational forces that there will be relative attraction between the Earth and the moon and between the Earth and the Sun. The tide generally differ with low tide and high tide. Temporal resolution is determined by altitude and orbit of the satellite as well as its sensor characteristics. The repetition rate and the temporal resolution of earth observing satellites are 14-16 days. Meteorological satellites such as meteosat take 8 to 15 min have extremely shorter repetition rates.

The temporal resolution is lower through clouds in some situations of sensors which verify visible or infrared radiation that does not penetrate through clouds. Since many areas of the earth are often covered by clouds, these areas cannot be captured when a satellite position is over them.

Images of an area taken at different times like monthly, yearly can be used for multitemporal analysis. They allow analysis of the following, just to give a few examples seasonal changes of vegetation, the expansion of cities over decades, documentation of forest clearance in the tropical rainforest etc. Temporal resolution is applicable to polar orbiting satellites. But defining it more precisely, temporal resolution for a polar orbiting satellite is the amount of time that the satellite takes to revisit and recapture a specific place. It is also commonly referred to as a satellite’s revisit period. For example, temporal resolution of a single sentinel-2 satellite is 10 days. This means one sentinel-2 satellite can recapture a particular place by revisiting again.

One confusing aspect of temporal resolution can be evaluated with high and low temporal resolution. These are relative terms. The lower the period of time between two consecutive captures of the same area, the higher the temporal resolution. Advanced temporal resolution simply means that the satellite revisits and captures data of a particular place regularly. A satellite with temporal resolution of 1 day is said to have a higher temporal resolution relative to a satellite with temporal resolution of 15 days. In some situations many number of polar orbiting satellites are used for better temporal resolution. sentinel-2 mission consists of two sentinel satellites with each having a revisit period of 10 days. Constellation of two satellites provides data of a particular site every five days making the advanced temporal resolution five days.

Importance of multi-temporal satellite data is the ability to capture images and record data of the same place at different intervals of time can be leveraged for multiple purposes. Some applications of multi-temporal satellite imagery are listed below:

• Monitoring changes in crop and agricultural pattern.

• Monitoring processes like urban development, electrification, deforestation.

• Weather status can be easily concluded.

• Tracking natural and man-made disasters and recovery that follows.

• Having a look on the surface of the earth.

• Data of imagery sites may not be clearly visible sometimes due to clouds movement.