Remote sensing
- 1. Remote Sensing Submitted by : Nandita Purohit (M.Sc. Zoology)
- 2. contents 1. Introduction 2. Physical basis of RS 3. Remote Sensing process ā Platforms and sensors for RS ā RS satellites ā Systems for Data Collection ā Data analysis 4. Application 5. Advantages 6. Disadvantages
- 3. Introduction ā¢ Remote sensing is the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation at a distance (typically from satellite or aircraft). ā¢ Special cameras collect remotely sensed images, which help researchers "sense" things about the Earth. ā¢ These systems may be configured to collect data in just one band of the electromagnetic spectrum, in multispectral remote sensing radiant energy is recorded in multiple bands and hyperspectral remote sensing instruments acquire data in hundreds of contiguous spectral bands.
- 4. A LiDAR (Light Detection and Ranging) image created with data collected by NOAA's National Geodetic Survey.
- 5. Physical basis for remote sensing ā¢ In remote sensing observations of the target (the physical object or geographic area) are made from a distance, using specialized instruments called sensors. ā¢ Reflected radiation from the objects are recorded by sensors such as photographic camera, scanners or radiometers which are mounted on suitable platforms
- 6. Remote sensing process The remote sensing process involves data collection and analysis in a systematic way which can be seen in the figure
- 7. Platforms and sensors for remote sensing ā¢ For remote sensing data acquisition and the platforms could be ground based (hydraulic lift), aerial (balloon helicopter and aircraft), and space borne satellites. ā¢ Scanners are most commonly used in satellites to overcome the problem of returning photographic film on earth. ā¢ The two most important components of sensors are their spatial and spectral resolution ā¢ The spatial resolution is defined by the smallest feature that can be SEEN by the sensors, where as the spectral resolution is the range and number of bands within the spectrum to which a sensor is sensitive.
- 8. Remote sensing satellites 1. LANDSAT ā¢ NASA launched a series of LANDSAT satellites over the period of more than three decades the landsat missions have used various devices for collecting the information like the return beam vidicon camera (RBVC) 2. SPOT ā¢ The earth resource satellite of France was launched in February 1986. It has highly sensitive sensors, which can collect information from different directions. It can detect details as small as 10m and resolve heights with an aggregation of less than 5 km. 3. IKONOS ā¢ IKONOS was the first commercial high resolution satellite launched in 1999, with optical sensor assembly (OSA) having four spectral bands (1- 4). The data are used for small to medium scale topographic mapping and also for updating the existing topographic maps.
- 9. 4. Indian remote sensing satellites ā¢ Indian remote sensing satellites have been of immense use in hydrology, forestry, urban and land use planning and geology to identify and monitor various coastal zone features, also it has helped to study the natural resource management. 5. NOAA ā¢ The National oceanic and atmospheric administration polar orbiting satellites (NOAA 10 and NOAA11) carry the advanced high resolution radiometer, a passage system that is sensitive to visible and infrared wavelengths. 6. GOES ā¢ Geostationary operational environmental satellites known as GOES-8 and GOES-9 provide the daily infrared and visible images of the weather.
- 10. Systems for data collection ā¢ Remote sensing data are collected using either passive or active remote systems. ā¢ Remote sensing systems collect analogue and digital data. ā¢ The satellite or aerial scanner data are processed on board, and related down to the ground receiving station. ā¢ The data are stored temporarily on high density data tapes (HDDT). The two types of system for collecting information are
- 12. Passive system ā¢ Passive system consists of an array of small sensors for detectors which record the amount of electromagnetic radiation reflected and/or emitted from the Earth surface in the visible on near infrared and far red regions. ā¢ For receiving the emission in the visible light various types of camera and vidicon cameras are used. ā¢ Several types of photographic films used in the cameras are: panchromatic, black and white - topography; infrared - land and water distribution; false color - vegetation; thermal infrared - microwave emission and x and gamma rays.
- 13. Active Systems ā¢ An active system uses its own source of electromagnetic radiation and measures the intensity of the return signal as digital numbers. ā¢ The system includes radar pulse, photoflash beams and laser beams and use the artificial source of energy resources for remote sensing. ā¢ Electromagnetic energy is propagated near the sensor and bound towards the sensor system. ā¢ RADAR (radio detection and ranging), SAR (synthetic aperture radar), SONAR (sound navigation and ranging), LiDAR (light detection and ranging) are all examples of active systems for data collection
- 14. Data analysis ā¢ The analysis of remotely sensed data includes a variety of image processing techniques that include analog (visual) image processing of image data, the digital image processing of digital data. ā¢ The remote sensing data interpretation can be applied for a number of purposes in geology, forestry, agriculture, soil mapping, ecology, water resources and wildlife management.
- 16. Analogue (visual) image processing ā¢ The principles of photo interpretation was developed for aerial photography and are not applicable to all remote sensing visual data products. ā¢ The visual image analysis includes image interpretation and photogrammetric measurement on the basis of the size, shape, shadow, color, pattern, texture, and site and precise measurement of object. ā¢ This depends on the ability of a person to draw conclusions either by direct and spontaneous recognitions of object or by using the reasoning process.
- 17. Digital image processing of digital data ā¢ The major type of digital image processing involve statistical and syntactical pattern , photogrammetric image processing of the stereoscopic imagery, hyperspectral data analysis, expert system and neural network image analysis. ā¢ In digital image processing instead of human vision computer is instructed to perform and interpretation according to certain conditions. ā¢ The goal of image classification is to convert image data into thematic data (thematic characteristics include land use, land cover, soil type, etc).
- 18. Applications ā¢ Remote sensing has a wide range of applications in many different fields: ā¢ Coastal applications: Monitor shoreline changes, track sediment transport, and map coastal features. Data can be used for coastal mapping and erosion prevention. ā¢ Ocean applications: Monitor ocean circulation and current systems, measure ocean temperature and wave heights, and track sea ice. Data can be used to better understand the oceans and how to best manage ocean resources.
- 19. contd. ā¢ Hazard assessment: Track hurricanes, earthquakes, erosion, and flooding. Data can be used to assess the impacts of a natural disaster and create preparedness strategies to be used before and after a hazardous event. ā¢ Natural resource management: Monitor land use, map wetlands, and chart wildlife habitats. Data can be used to minimize the damage that urban growth has on the environment and help decide how to best protect natural resources.
- 21. Advantages of remote sensing ā¢ Synoptic view: a large area can be covered by a single image as produced from different sensors and satellites enabling us to see all the features of the area together ā¢ Repetivity: the data for any area can be obtained repeatedly at regular interval of time which help to monitor changes over time ā¢ Mapping of different terrain: accurate data can be collected for the inaccessible areas like mountains, swampy areas, and thick forests.
- 22. contd. ā¢ Management planning: the digital data in different spectral regions can be processed and analyzed using a computer to get baseline information for a suitable management of an area. ā¢ Cost effective and time effective: if used efficiently, remote sensing could be cost effective and less time consuming for monitoring large areas.
- 23. Disadvantages of remote sensing ā¢ Expensive to build and operate. ā¢ Measurement uncertainty can be large. ā¢ Resolution is often coarse. ā¢ Data interpretation can be difficult. ā¢ One needs to understand theoretically how the instrument is processing the measurements. ā¢ Knowledge of the phenomena should be well addressed while sampling.