Remote Sensing platforms and types of RS.pptx

Remote sensing platform and types

1. Types of Remote Sensing Platforms Platforms are commonly called the vehicles or carriers for remote sensing devices (camera, sensors) Platforms equipped with remote sensors may be situated on the ground , on a balloon , on a Kite , on an aircraft (or some other platform within the Earth’s atmosphere), or on a spacecraft or satellite outside the Earth’s atmosphere. Platforms gives stability for remote sensing Altitude determines the ground coverage, which is a key factor for selection of a platform. Besides the altitude, there are other parameters such as Resolution and Nature of Data Requirement which are responsible for determining ground coverage and resolution of image data and hence one platform may have different sensors acquiring data at different ground coverage with different image resolutions.

2. There are three types of remote sensing platforms: Ground-based platforms : F or detailed surface information. Can be placed on ladder, crane, tall buildings etc. The data collected by this platform are used for bridge and dam monitoring, landslide and soil erosion mapping, architectural restoration, facilities inventory, crime and accident scene analysis, manufacturing, etc. Air-borne platform: Primarily used for aerial photographs . airplanes, helicopters, balloons and even rockets are commonly used to collect very detailed images. They are capable of operating over a wide range of altitudes ranging from the sea level to stratosphere. Aerial platforms are primarily stable wing aircrafts, although helicopters are occasionally used. Aerial photographs have been a main source of information about the Earth’s surface almost since the beginning of aviation more than a century ago.

3. Advantages of Air-borne platforms • aircraft can fly at relatively low altitudes thus allowing for very good spatial resolution • aircraft can easily change their schedule to avoid weather problems such as clouds, which may block a passive sensor’s view of the ground • last minute timing changes can be made to adjust for illumination from the Sun, the location of the area to be visited and additional revisits to that location • sensor maintenance, repair and configuration changes can be easily made to aircraft platforms • aircraft flight paths know no boundaries except political boundaries however, getting permission to intrude into foreign airspace could be a lengthy and frustrating process.

4. Space-borne Platform In space borne remote sensing, sensors are mounted on-board a spacecraft (space shuttle or satellite) orbiting the Earth. They are used for remote sensing, weather monitoring, communication and navigation purposes They are not affected by earth’s atmosphere. Global coverage. But low resolution They can polar satellites (low orbit), geostationary (high orbit) and Navigation (medium orbit) Satellites remote sensing has many advantages (as you all know)

5. Types of Remote Sensing 1. Based on platform Ground-based RS Air-borne RS Space-borne RS 2. Based on energy source Active RS Passive RS 3. Based on imaging media Photographic imaging Digital imaging 4. Based on regions of spectrum Optical RS Photographic RS Thermal RS Microwave RS

6. 5. Based on number of spectral bands Panchromatic RS (visible band) Multispectral RS ( Hyperspectral RS Elaboration Based on energy source: Active Remote Sensing: Such sensors use their own energy source for illumination. They emit radiation, it hits the target and reflected back to the sensor and then gets sensed and measured. Advantage is to do the RS anytime of the day or season. Can be used to examine the wavelengths that are not sufficiently provided by the sun. Examples: SAR, RADAR, SONAR, LIDAR, Camera with Flash light Passive Remote Sensing: When sensor uses energy released by other sources such as sun or naturally emitted thermal and microwave energy, is called passive remote sensing. Its done in primarily in visible band in the day time but also in thermal and microwave region all the time as well Example: film photography, infrared, charge-coupled devices, and radiometers Types of Remote Sensing…….

7. Types of Remote Sensing……. Based on imaging media Photographic imaging : e.g. aerial photographs. Its possible only in photographic region of the spectrum which lies between 0.3 to 0.9 micrometer. Beyond this range, digital imaging is the only option. This system requires continuous supply of films and processing on ground after the photos have been taken Digital imaging : Satellite remote sensing. Its capable of much higher spectral resolution. Multispectral photographic systems are used for wider coverage of spectral bands. Digital imaging can be directly transmitted to the computer system.

8. Types of Remote Sensing……. Based on regions of spectrum Optical RS Photographic RS Thermal RS Microwave RS Optical remote sensing is done with the help of lenses and mirrors and that’s why its called optical RS. Optical and photographic remote sensing records reflected energy from earth surface. These sensors generally use sun as a source of energy (exception- LIDAR) Thermal and Passive microwave remote sensing uses emitted energy from objects. However active microwave RS is also done which use backscattered energy recorded by sensor. For greater detail, refer to the following two images in next two slides

9. Types of Remote Sensing……. Based on number of bands Panchromatic RS Collection of reflected, emitted or backscattered energy from a single band of spectrum Done for single band of the spectrum Usually done in visible range 2. Multispectral RS Collection of reflected, emitted or backscattered energy from a multiple bands of spectrum Can be performed in optical, thermal and microwave bands 3. Hyperspectral RS - Its an extension of the technique used in multi-spectral RS. - Its generally used in optical band of the spectrum - It can sense in hundreds of narrow spectral sub-bands i.e. its capable of sensing finer reflectance from different objects on earth surface like crop and vegetation study