Dynamic Range: Digital Imaging: Glossary: Learn. Monitoring Vegetation From Space. Lidar to DEM. Introduction Geographic Information Systems (GIS) often store representations of continuous surfaces representing physical properties such as elevation, temperature, water depth, etc., which can be approximated to a reasonable level of accuracy by smooth, single valued functions of the form z=F(x,y). Often such a surface is stored as a regular grid—or raster—of data values.
When physically measuring the value of the surface, it is often impossible to collect data for every point on the surface. Instead, scientists collect a sample S of N spot measurements of the form (x,y,z) and reconstruct the continuous surface z=F(x,y) by interpolating the points in S. We are particularly interested in data sets collected using lidar—a remote sensing method that collects highly accurate and dense point samples that measure the height of a terrain.
Input lidar points shown in red (left) and corresponding DEM (right) with color representing height. Issues Our Approach Our Results Publication P. Links. Image Scale Math. Image Scale Math Educator Guide Audience: EducatorsGrades: 6-8 Image Scaling is an important first step that all astronomers perform in understanding image-type data produced by satellites and telescopes. Each activity in this booklet has an image. The physical size of the object shown in the image is listed in the activity. Students measure the size of the image and divide the physical size by the image size to determine the scale factor. They can then use the scale factor to investigate sizes of objects within the image. Image Scale Math [7MB PDF file] The application of remote sensing technology to marine fisheries: an introductory manual. A sensor is a device which detects emitted or reflected electromagnetic radiation and converts it to a physical value that can be recorded and processed.
Sensor systems may be divided into two major categories: 4.1 Global Acquisition Systems The global acquisition sensors commonly used for oceanographic studies are aerial, vidicon and underwater cameras. Underwater cameras are not considered in this manual. 4.1.1 Aerial cameras These are one of the simplest forms of imaging system used in fisheries and ocean studies (refer to Figure 4.1). Cameras have been in use for a long time and a great deal of knowledge has accumulated regarding techniques of image recording, image interpretation and data extraction. One of the major disadvantages in the use of aerial cameras is the constraint imposed by adverse weather conditions. The quality of a photograph will depend on several interrelated factors: focal length; angle of view; scale; contrast; resolution; and film speed. 4.1.1.1 Focal length (f):
Diffuse sky radiation. A spectrum taken of blue sky clearly showing solar Fraunhofer lines and atmospheric water absorption band. Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or suspensoids in the atmosphere. It is also called skylight, diffuse skylight, or sky radiation and is the reason for changes in the color of the sky. Of the total light removed from the direct solar beam by scattering in the atmosphere (approximately 25% of the incident radiation when the sun is high in the sky, depending on the amount of dust and haze in the atmosphere), about two-thirds ultimately reaches the earth as diffuse sky radiation.
The important processes in the atmosphere (Rayleigh scattering and Mie scattering) are elastic processes, by which light can be deviated from its path without being absorbed and with no change in wavelength. Color[edit] Clear blue sky. Neutral points[edit] Under an overcast sky[edit] See also[edit] Lecture3_6.pdf (application/pdf Object) Earth's radiation balance. These maps show monthly net radiation in watts per square meter. Places where the amounts of incoming and outgoing energy were in balance are yellow. Places where more energy was coming in than going out (positive net radiation) are red. Places where more energy was going out than coming in (negative net radiation) are blue-green. The measurements were made by the Clouds and the Earth's Radiant Energy System (CERES) sensors on NASA’s Terra and Aqua satellites.
Over the course of a year, the most obvious pattern is seasonal changes in net radiation. Incoming sunlight increases in the hemisphere experiencing summer, which makes the energy imbalance strongly positive (more watts of energy coming in than going out). Earth's radiation balance or Earth's energy balance describes the incoming and outgoing thermal radiation.
Equation[edit] The incoming solar radiation is short wave, therefore the equation below is called the short wave radiation balance Qs:[citation needed] Ql = AE = AO - AG. The Earth's Magnetic Field. The Earth'sMagnetic Field The Earth has a substantial magnetic field, a fact of some historical importance because of the role of the magnetic compass in exploration of the planet. Structure of the Field The field lines defining the structure of the magnetic field are similar to those of a simple bar magnet, as illustrated in the following figure. It is well known that the axis of the magnetic field is tipped with respect to the rotation axis of the Earth. Thus, true north (defined by the direction to the north rotational pole) does not coincide with magnetic north (defined by the direction to the north magnetic pole) and compass directions must be corrected by fixed amounts at given points on the surface of the Earth to yield true directions.
Van Allen Radiation Belts As illustrated in the adjacent figure, the charged particles are reflected at "mirror points" where the field lines come close together and the spirals tighten. Origin of the Magnetic Field The Earth's Magnetosphere. Radiant flux. Units[edit] The SI unit of radiant flux is the watt (W), which has dimensions of energy/time or, in SI units joules/second. See also[edit] References[edit] Light. Light is part of the electromagnetic spectrum Light is a electromagnetic wave. This wave has a wavelength that can be measured in meters. Of course light waves are very small. Shown below is a chart showing the relationship between the length of the light wave in nanometers as a function of the color of light we humans are able to observe.
It turns out that plants respond to these wavelengths (and more!). Light is the driving force, the energy for photosynthesis. Light is just one part of the electromagnetic spectrum. Starlight is the solar power of the earth All biological energy comes from sunlight and this energy encompasses the range of the electromagnetic spectrum known as light. If you remember that visible light covers the range of wavelengths from 400 to 700 nm, then you can see here that sunlight includes waves that are ultraviolet (280 to 400 nm) and waves that are infrared (greater than 700 nm). Chlorophyll absorbs blue and red light Excited electrons can fluoresce.
Optical_Radiation_Models_NB.pdf (application/pdf Object) Principles of Remote Sensing - Centre for Remote Imaging, Sensing and Processing, CRISP. Optical remote sensing makes use of visible, near infrared and short-waveinfrared sensors to form images of the earth's surface by detecting thesolar radiation reflected from targets on the ground.
Different materials reflect and absorb differently at different wavelengths. Thus, the targets can be differentiated by their spectral reflectance signatures in the remotely sensed images. Optical remote sensing systems are classified into the following types, depending on the number of spectral bands used in the imaging process. Solar Irradiation Optical remote sensing depends on the sun as the sole source of illumination. After passing through the atmosphere, the solar irradiation spectrum at the ground is modulated by the atmospheric transmission windows. Solar Irradiation Spectra above the atmosphere and at sea-level. Spectral Reflectance Signature When solar radiation hits a target surface, it may be transmitted, absorbed or reflected.
Reflectance Spectrum of Five Types of Landcover. Wave-particle duality. Sections 27.4 - 27.6 The Compton effect Although photons have no mass, they do have momentum, given by: Convincing evidence for the fact that photons have momentum can be seen when a photon collides with a stationary electron. Some of the energy and momentum is transferred to the electron (this is known as the Compton effect), but both energy and momentum are conserved in such a collision. Applying the principles of conservation of energy and momentum to this collision, one can show that the wavelength of the outgoing photon is related to the wavelength of the incident photon by the equation: Wave-particle duality To explain some aspects of light behavior, such as interference and diffraction, you treat it as a wave, and to explain other aspects you treat light as being made up of particles.
Wave-particle duality is not confined to light, however. The de Broglie wavelength In 1923, Louis de Broglie predicted that since light exhibited both wave and particle behavior, particles should also. How Electromagnetic Radiation Interacts with Matter. What is polarization? Definition from WhatIs.com - see also: wave polarization. Polarization, also called wave polarization, is an expression of the orientation of the lines of electric flux in an electromagnetic field ( EM field ).
Polarization can be constant -- that is, existing in a particular orientation at all times, or it can rotate with each wave cycle. Polarization is important in wireless communications systems. The physical orientation of a wireless antenna corresponds to the polarization of the radio waves received or transmitted by that antenna. Thus, a vertical antenna receives and emits vertically polarized waves, and a horizontal antenna receives or emits horizontally polarized waves.
The best short-range communications is obtained when the transmitting and receiving (source and destination) antennas have the same polarization. The least efficient short-range communications usually takes place when the two antennas are at right angles (for example, one horizontal and one vertical). The effect of polarization on visible light can be striking. Electromagnetic Radiation: Field Memo. All near-field readings require special attention. In general, readings taken closer than one wavelength require measurement of both the E and H fields. A good general rule of thumb is "Measure the E field above 300 MHz and measure both-the E field and the H field below 300 MHz". For example, when surveying radio frequency heat sealer machinery at 27 MHz (λ = 11.1 meters, or 36.4 feet), both E and H must be measured, since the measurement is in the near-field. Two wavelengths at 27 MHz is 22.2 meters (72.8 feet) away.
While taking measurements in the near-field, you may notice the values for E and H vary considerably from point to point. The boundaries shown in Figure 1. should not to be considered rigid, but they are values obtained by consensus to help categorize wave motion characteristics and behavior into regions. Perhaps in a summary we can best look at two examples. OSHA's compliance instruments are small, light-weight, and battery operated appliances. Figure 2. Categories of Waves. Waves come in many shapes and forms. While all waves share some basic characteristic properties and behaviors, some waves can be distinguished from others based on some observable (and some non-observable) characteristics.
It is common to categorize waves based on these distinguishing characteristics. Longitudinal versus Transverse Waves versus Surface Waves One way to categorize waves is on the basis of the direction of movement of the individual particles of the medium relative to the direction that the waves travel. Categorizing waves on this basis leads to three notable categories: transverse waves, longitudinal waves, and surface waves. A transverse wave is a wave in which particles of the medium move in a direction perpendicular to the direction that the wave moves. Suppose that a slinky is stretched out in a horizontal direction across the classroom and that a pulse is introduced into the slinky on the left end by vibrating the first coil up and down.
Check Your Understanding 1. 3. Radar Basics - Polarisation of Electromagnetic Waves. Polarization of electromagnetic waves Figure 1: missile-guidance radar S 75 „Fan Song E” Source of the picture: www.pvo.guns.ru The radiation field of an antenna is composed of electric and magnetic lines of force. These lines of force are always at right angles to each other. The electric field determines the direction of polarization of the wave.
When a single-wire antenna is used to extract energy from a passing radio wave, maximum pickup will result when the antenna is oriented in the same direction as the electric field. Figure 2: vertically linear polarisised electric field (blue) and horizontally linear polarisised electric field (red) Figure 2: vertically linear polarisised electric field Figure 3: horizontally linear polarisised electric field Linear Polarization Vertically and horizontally mounted receiving antennas are designed to receive vertically and horizontally polarized waves, respectively. Two planes of polarization are used mainly: Circular Polarization Depolarisation. Tutorials :: SEOS LMS. Lec-6 Remote Sensing Introduction. Lexikon der Fernerkundung.
Principles of Remote Sensing - Centre for Remote Imaging, Sensing and Processing, CRISP. Dr. S. C. Liew Centre for Remote Imaging, Sensing and ProcessingNational University of SingaporeBlk S17/SOC1 Level 2, Lower Kent Ridge RoadSingapore 119260 Email: scliew@nus.edu.sg URL: www.crisp.nus.edu.sg © 1997, 2001 CRISP. All rights reserved. This tutorial is part of the "Space View of Asia, 2nd Edition" CD-ROM produced by the Centre for Remote Imaging, Sensing and Processing (CRISP) at the National University of Singapore.
Click to start the Tutorial. ISRO to launch Remote Sensing Resourcesat in February.