Remote Sensing and GIS Application Lecturer Ruba Yousif

Remote Sensing and GIS Application Lecturer Ruba Yousif Hussain Third Year 1

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Concepts and Foundations of Remote Sensing is the collection of data without directly measuring the object. It relies on the reflectance of natural or emitted electromagnetic radiation. Data and Information The remotely collect data may be analyzed to obtain information about the objects, areas, or phenomena being investigated. Aerial Imagery And Satellite Imagery 1 Airborne Imagery introduces the topics of aerial photogrammetry. 2 Satellite Imagery 2

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Difference between aerial imagery and satellite imagery The chief difference between aerial imagery and satellite imagery is now one of scale. Because airborne imaging is usually at a much larger scale than is satellite imaging, aerial images are presently more suitable for engineering works. However, the highway planning has been greatly assisted with satellite imagery. An advantage of airborne remote sensing, compared to satellite remote sensing, is the capability of offering very high spatial resolution images ( 20 cm or less ). 3

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Camera Systems 1 Digital camera 2 Film based camera Digital and film based cameras both use optical lenses. Whereas film based cameras use photographic film to record an image, digital cameras record image data with electronic sensors. One chief advantage to digital cameras is that the image data can be stored, transmitted, and analyzed electronically. The photo or the film itself can be scanned, thus preparing the image data for electronic processing. Types of Sensors 1 Photography 2 Infrared 3 Multispectrum ( For example. SPOT ) 4 Hyperspectral collects more than 16 bands 5 Radar 6 Laser ( Li. DAR = Light Detection And Ranging ) The main difference between multispectral and hyperspectral is the number of bands and how narrow the bands are. Multispectral imagery generally refers to 3 to 10 bands. Each band is obtained using a remote sensing radiometer. A hyperspectral image could have hundreds or thousands of bands. 4

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Electromagnetic Spectrum The "visible" portion of such a plot is an extremely small one, since the spectral sensitivity of the human eye extends only from about 0. 4 µm to approxi mately 0. 7 µm. The color "blue" is ascribed to the approximate range of 0. 4 to 0. 5 µm, "green" to 0. 5 to 0. 6 µm, and "red" to 0. 6 to 0. 7 µm. Ultraviolet (UV) energy adjoins the blue end of the visible portion of the spectrum. Adjoining the red end of the visible region are three different categories of infrared (IR) waves: a reflected IR ( ranging from about 0. 7 µm to about 3. 0 µm near IR (from 0. 7 to 1. 3 µm), mid IR (from 1. 3 to 3 µm), and b thermal IR ( beyond 3 to 14 µm ). At much longer wavelengths ( 1 mm to 1 m ) is the microwave ( for example , radar ) portion of the spectrum. Microwave Remote Sensing provides useful information about the Earth's atmosphere, land ocean. A microwave radiometer is a passive device which records the natural microwave emission from the earth. 5

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Electromagnetic Spectrum 6

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Photograph vs. Image In remote sensing, the term photograph is reserved exclusively for images that were detected as well as recorded on film. The more generic term image is used for any pictorial representation of image data. Thus, a pictorial record from a thermal scanner (an electronic sensor) would be called a "thermal image, " not a "thermal photograph, " because film would not be the original detection mechanism for the image. Because the term image relates to any pictorial product, all photographs are images. Not all images, however, are photographs. Image is actually composed of a two dimensional array of discrete picture elements, or pixels. The intensity of each pixel corresponds to the average brightness, or radiance, measured electronically over the ground area corresponding to each pixel. Digital images are comprised of many pixels, each of which has been assigned a digital number ( DN ) . The digital number represents the brightness level for that specific pixel. For example, in eight bit ( 2 ) imagery, the 256 brightness levels ranges from 0 ( black ) to 255 ( white ). 7

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Energy Interactions with Earth Surface Features Basic interactions between electromagnetic energy and an earth surface feature 8

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Types of remote sensing instruments Active and Passive An active sensor is a sensing device that requires an external source of power to operate : active sensors contrast with passive sensors , which simply detect and respond to some type of input from the physical environment. Examples Cameras are active sensors when the photographer uses flash. It illuminates its target and measure the reflecting energy back to the camera . Cameras are passive sensors when the photographer does not use the flash . Because the camera is not sending the source of light. It uses naturally emitted light from the sun. 9

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Platform A platform is the vehicle or carrier for remote sensors for which they are borne. In Meteorology platforms are used to house sensors which are obtain data for remote sensing purposes, and are classified according to their heights and events to be monitored. Image Resolution Image resolution defines the ability of a sensor to distinguish between spatial characteristics of objects on the earth's surface. 10

Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain Questions 1. What are the processes involved in remote sensing? Answer This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information. In much of remote sensing, the process involves an interaction between incident radiation and the targets of interest. 2. How does multispectral imaging work? Answer A multispectral image is one that captures image data at specific frequencies across the electromagnetic spectrum. The wavelengths may be separated by filters or by the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range, such as infrared. 3. What is hyperspectral imaging? Answer Hyperspectral imaging , like other spectral imaging, collects and processes information from across the electromagnetic spectrum. The goal of hyperspectral imaging is to obtain the spectrum for each pixel in the image of a scene, with the purpose of finding objects, identifying materials, or detecting processes. 4. What is a spectral image? Answer Spectral imaging is a branch of spectroscopy and of photography in which a complete spectrum or some spectral information is collected at every location in an image plane. Spectral images are often represented as an image cube, a type of data cube. 11