Remote Sensing is the science and art of obtaining information about an object, area or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area or phenomenon under investigation. If the information is collected through satellites it is called Satellite Remote Sensing (SRS). Remote Sensing along with its allied technologies has become an industry in itself. The basic principle of remote sensing is based on the interaction of electromagnetic radiation with atmosphere and the earth. Electromagnetic radiation reflected or emitted from an object is the usual source of remote sensing data. However, any media such as gravity or magnetic fields can be utilized in remote sensing. The characteristics of objects can be determined, using a reflected or emitted electromagnetic radiation from the object. Each object has unique and different characteristics of reflection or emission under different environmental conditions.
Remote sensing is the technology used to identify and understand the objects under different environmental conditions. A sensor receives the electromagnetic radiation emitted and reflected by various earth surface features. These received radiations are analyzed and converted into information about the object under investigation. Therefore, remote sensing offers an efficient and reliable means of collecting the information required for various purposes. Due to its unique ability to furnish synoptic views of larger areas, satellite remote sensing is being effectively utilized in several areas for sustainable agricultural development and management. These areas include cropping system analysis; agro-ecological zonation; quantitative assessment of soil carbon dynamics and land productivity; soil erosion inventory; integrated agricultural drought assessment and management.
Pakistan Space and Upper Atmosphere Research Commission (SUPARCO) is committed to the peaceful uses of space and space technologies. It has been pursuing Satellite Remote Sensing (SRS) and Geographic Information System (GIS) application programs for the past 30 years. It has established the requisite facilities and developed necessary expertise. SUPARCO acquires and archives SRS data from French SPOT series of satellites. The satellite data and related services are provided to different users within and outside the country. Information pertaining to status of crops is acquired through satellite remote sensing. This information and its calibration through ground truth surveys, provides timely and accurate data on crop acreage estimates, yield forecasts, early warning and crop stress. This helps in food security and better management of agriculture sector in Pakistan.
There are two main crop growing seasons in Pakistan; the Kharif and the Rabi. By tradition, the crops are counted among their seasons of harvest. All crops harvested around spring or follow up are called Rabi as the word literally means spring. The crops harvested in autumn, on the same analogy, are called Kharif crops. Similarly, the crops are counted in the financial year of harvest. Major Rabi crops include wheat, brassica, gram, fodders and others. The Kharif crops include sugarcane, cotton, rice, maize, fodders and legumes. Crop calendar plays a vital role to determine the satellite data acquisition schedule for crop area, yield and production estimation in Pakistan.
Satellite data vary in terms of their sensitivity to ground features with respect to sensors, its coverage in a single scene, spectral, spatial and temporal resolution and topographic effects. The SPOT satellite data cover an area of 3600 Km² to 4800 Km² in single observation with different acquisition angles. Spatial resolution is an important parameter of the satellite data for the estimation of crop area. Various land surface features such as field boundary, roads, canals etc. can be differentiated, once high resolution satellite data is available SUPARCO uses SPOT 5 data for the crop area estimation. A maximum of 10 meter resolution data can be used to estimate crop area with more than 90% accuracy and the lowest sampling and non-sampling errors. SUPARCO generally uses 5 meter multispectral resolution data produced through spatial enhancement of 10 meter multispectral images from 5 meter panchromatic image.
Data quality control through validation system makes the acquisition more reliable for area estimates. This helps to work out crop area estimates with better accuracy. Acquisition dates or time of the satellite data is extremely crucial for the final crop area estimates by removing the impact of other crops. Acquisition dates correspond to the start and peak time of the photosynthetic activity and times of maturity. In Pakistan, there is 6-8 weeks difference in cropping pattern from southern latitude of 24 degree to 34 degree in North. These two elements play important role in defining the time schedule for satellite data acquisitions. These dates change with zone to zone and cropping seasons. High resolution satellite data for crop area estimation are acquired twice during the growing season, once at sowing and secondly during peak growth season.
REMOTE SENSING AND FLOOD 2010 IN PAKISTAN
Natural disasters of any kind play havoc with and cause huge losses to both humans and properties. Current situation of flooding in Pakistan is one of the true examples of how floods of such a magnitude can put an entire country in chaos and adversely affect its economy. These floods affected all the provinces of the country badly. In the wake of such a wide spread disaster, remote sensing data once again proved its importance both for relief and rescue efforts. The availability of temporal remote sensing data from Landsat and ASTER has made it possible to map the flood extents in Pakistan, and track the movement of the flood from north to south of the country. Temporally mapped flood extent helps the authorities to monitor the progress of the floods, how and from where to access the affected urban areas to provide relief and rescue in a timely manner. It also helps in determining which of the flood protection bunds (levees) needs reinforcement, deciding where to breach to the bunds to save some of the cities, barrages and other important installations. In future, these mapped flood extents can help the concerned authorities for damage assessment of urban areas, road infrastructure, and crops, as well as to demarcate and designate nonexistent floodplain boundaries.
The Climate Change Cell at University of Agriculture Faisalabad is working on Satellite Remote Sensing under project of “Indus River Basin Research Activities” to estimate crop yield. The activity addresses potential impacts of climate change on water resources and crop productivity for ultimate goal of disaster risk reduction. Director External Linkages and Head of Climate Change Cell Prof. Dr. Ashfaq Ahmad and his team dedicated well to face variable impacts of climate change and he rated Pakistan a “high risk” country in the global rankings for Climate Change Vulnerability Index. So, it is the need of time to take extra measures such as Remote Sensing Approach for disaster risk reduction.