Multi date images mean satellite image/aerial photographs captured by sensor on different dates but belongs to same location or area covered by that sensor. These multi date images are very useful and advantageous in remote sensing to find out changes with time in natural as well as man-made features.
Multi date images also called as multi temporal images. As it is understood that satellite are ideals for monitoring changes of earth surface feature over time. The repeat cycles of satellite around the earth are measured either in days or weeks.
It can be understand by the example, suppose if someone wants to analyze the change in urban growth of any selected city in last three decades or some other given time then change detection analysis is process used to ascertain changes.
For the above example, urban are is mapped for three different periods and change detection performed using image processing tools. BY this process change detection in urban area can be calculated as well as biggest advantage of this process that it will also provide spatial distribution of urban changes.
The same advantages of multi date can be explained by below Land Use/Land Cover map prepared using satellite images of 1989, 2000 and 2003. These images are classified in to
In this classification, seven land use categories created to find the changes in natural feature and man-made feature from 1989 to 2003. BY using these classified LULC map, change detection analysis for different periods such as 1989 to 2000, 2000 to 2003 and 1989 to 2003 can be performed.
As it provide the past changes which can be used to understand future scenarioin any above mentioned change detection studies. The monitoring through temporal or multi date images can facilitate analysis of crop growth and forest change as well as drought and flood conditions.
Increase in stress on water bodies due to surrounding polluting activities can be monitored over time using multi date images.
This multi date/temporal images can be used to map pre and post impact after any hazard/disaster event such as pre and post analysis after Tsunami/earthquake. These multi date image can help to assess the impact of disaster.