Remote Sensing Data Supply From NRSA Data Centre For Disaster Management

Dr N. Aparna
Incharge user Services
NAtional Remote Sensing Agency, India
aparna_n@nrsa.gov.in

A.V.Ramani
Scientist D
National Remote Sensing Agency, India
ramani_av@nrsa.gov.in

D.Chandrasekharan
Manager DD&US
NAtional Remote Sensing Agency, India
chandrasekharan_d@nrsa.gov.in

Joseph Arokiadas
Group Head NDC
National Remote Sensing Agency, India
joseph_a@nrsa.gov.in

Abstract :
India is a country which is very much into the Space Science Technology and also is interested to use the technology only for the kind. India has launched satellites ranging from 1Km to 1m in the remote sensing areas and several satellites in the communication areas. These satellites besides proving virtual inputs for taking the preventive measures by Hazard Zonation, Prior risk Assessment at local and regional level also helps in minimizing the loss of life and property through advanced warnings.

National Remote Sensing Agency (NRSA) plays a pivotal role in all aspects starting from programming the passes to data dissemination. NRSA acquires data from various satellites having various types of sensors. In emergencies, based on the requirement these satellites can be tilted or programmed and the data is disseminated through FTP to the required users or to the organizations within few hours of acquisition. Cloudy data can also be supplemented by microwave data like RADARSAT. This is possible due to the high end systems and improving of the data processing software. Also apart from this the electronic data transfer has helped in improving the services. The services have been extended world wide. Iran Earth Quake , Hurricane at Florida etc were planned and recorded with 24 hours and the data was supplied to the users accordingly

Data over any part of India can be acquired by using the constellation of satellites that we have. As and when an emergency requirement is put forth by users the following steps are taken up - Given inputs into the required format of path and rows of all the satellites. Finding the feasibility of all the satellites.

The data is acquired at Shadnagar, which is 60Km away from NRSA. In emergencies the required area data is extracted and transferred through space net link. This data will be processed and made available to the local users immediately. For non-local users data will be compressed and transferred electronically. A choice of data compression is given to the user based on their requirement and application. An attempt was made to test the Compression software like Mr. SID, ECW and JPEG and the compression ratios. The data has been compressed in the ratio of 1:2, 1:3, 1:4 and 1:5 times. The compressed data Mean, Standard Deviation and Min Max values are calculated and compared with the uncompressed data. The histograms and the scatter plots of all the bands were also compared after the compression

The effect of this compression on the image also studied and also arrives at the compression factor, which will be useful for data supply in case of emergency. It has been proposed that 1:2 ratio is agreed upon for the use the data for classification. Therefore if the user has no ground truth collection and would like to go for unsupervised classification he can opt for 1:2 compression ratio. In case the user wants to opt for supervised classification, he can opt for 1:5 compression rations. In case the data is required for only visual interpretation he can opt for 1:20 compression ratio.

Remote Sensing has become a tool for estimating the damage like inundation during floods, Road damages / Blockages during landslides, Locust warning etc. The data is useful only when it is acquired and disseminated in real time. In order to fulfill such a requirement we need to make use of the resources from the constellation of the available satellites. Choice of the satellite / sensor is decided based on the type of the disaster, area effected and the terrain. Some times if required we need to plan for stereo data, so that height estimations also can be done. After taking the necessary steps to plan and acquire the data the next important task ahead is sending the data to the user at the earliest. This requires deciding upon the appropriate compressions. The compressions are decided based on the type of the sensor and disaster. For fast access of data by the users, the data is put on the ftp site. The data is used to study the extent of damage and to decide on measures to prevent further damages. The disaster maps generated with the help of the data also helps in taking appropriate action in combating the disaster. Thus a timely acquisition, generation and dissemination of data help in saving valuable human life, diverting major catastrophes, and in developing protective measures in the event of future disasters.