Remote Sensing Waves transport energy

According to quantum theory, light may be considered not only as an electro-magnetic wave but also as a "stream" of particles called photons which travel at speed c, the vacuum speed of light. Each particle carries one quantum of energy Q = hf where: h is Planck's constant f is the frequency of the light Short wavelenghts  high energy Long wavelenghts  low energy Remote Sensing

4μm 7μm

Remote Sensing

Any object above 0K (-273°C) emits electromagnetic energy How much is given by the law of Stefan-Boltzmann M = ε σ T 4 where: σ is a constant ε is the emissivity coefficient For a blackbody, ε is = 1. A blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A blackbody in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black body radiation. Remote Sensing

The wavelength at which a black body radiation curve reaches a maximum is given by the Wien’s wavelength displacement law λ max = A / T where A = ~2898 μm K Remote Sensing

Rayleigh scattering occurs when particles are very small compared to the wavelength of the radiation. Rayleigh scattering causes shorter wavelengths of energy to be scattered much more than longer wavelengths  sky is blue Mie scattering occurs when the particles are just about the same size as the wavelength of the radiation. Water vapour is a common causes of Mie scattering  clouds are white Non selective scattering this occurs when the particles are much larger than the wavelength of the radiation. Water droplets and large dust particles can cause this type of scattering  haze and smog Scattering occurs when particles or large gas molecules present in the atmosphere interact with and cause the electromagnetic radiation to be redirected from its original path. 3 types of scattering: Remote Sensing

Absorption causes molecules in the atmosphere to absorb energy at various wavelengths. Ozone Absorbs the harmful (to most living things) ultraviolet radiation from the sun. Without this protective layer in the atmosphere our skin would burn when exposed to sunlight. Carbon dioxide Absorbs radiation strongly in the far infrared portion of the spectrum - the area associated with thermal heating - which serves to trap this heat inside the atmosphere. Water vapour Absorbs much of the incoming longwave infrared and shortwave microwave radiation. The presence of water vapour in the lower atmosphere varies greatly from location to location and at different times of the year Remote Sensing

E t + E r + E s + E a = E inc Remote Sensing

Radiance vs. Reflectance Radiance is the variable directly measured by remote sensing instruments. Radiance most often has units of watt/(steradian/square meter). Reflectance is the ratio of the amount of light leaving a target to the amount of light striking the target. It has no units. Reflectance is a property of the material being observed. Radiance depends on the illumination (both its intensity and direction), the orientation and position of the target and the path of the light through the atmophere. With effort, many of the atmospheric effects and the solar illumination can be compensated for in remote sensing data. This yields something which is called "apparent reflectance" and it differs from true reflectance in that shadows and directional effects on reflectance have not been dealt with. For many applications, radiance and apparent reflectance can be used interchangibly. However, since reflectance is a property of the target material itself, you will get the most reliable results using reflectance.

speculardiffuse Remote Sensing

clean water turbid water Remote Sensing

Remote Sensing

Resolutions Spectral: refers to the width of spectral bands. Radiometric: sensitivity to differences in the power of the incoming radiation. Geometric: minimum distance between objects perceived as separated (distinguishable detail) Temporal: period of time between two acquisition over the same area. Remote Sensing

8 bits 4 bits 3 bits2 bits Remote Sensing

10 m 20 m 40 m80 m Remote Sensing

LiDAR stands for Light Detection and Ranging, commonly known as Laser Radar Each time the laser is pulsed: –Laser generates an optical pulse –Pulse is reflected off an object and returns to the system receiver –High-speed counter measures the time of flight from the start pulse to the return pulse –Time measurement is converted to a distance (the distance to the target and the position of the airplane is then used to determine the elevation and location) –Multiple returns can be measured for each pulse

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High spatial resolution –Laser footprint on ground ≤ 0.50 meters –Typical density is 0.5 to 20+ pulses/m 2 –2 to 3 returns/pulse in forest areas Large volume of data –5,000 to 60,000+ pulses/hectare –10,000 to100,000+ returns/hectare –0.4 to 5.4+ MB/hectare Raw return data is a cloud of XYZ points Remote Sensing

Streams Remote Sensing

RGBRGB 3  0.65µm VIS 2  0.55µm VIS 1  0.48µm VIS 3  0.85µm NIR 2  0.65µm VIS 1  0.55µm VIS Natural colours False colours Remote Sensing

Water Forest Urban area Fields Remote Sensing

Whenever satellite images are visualized using the direct correspondence between the digital values of pixels and the intensity levels of primary colors on screen, they appear to be dark and poorly contrasted. Indeed, generally the digital values associated to the pixels do not cover the entire range of useable digital values. The sensibility of the sensor is tuned to avoid out-of-scale measurements, even when scanning over lowly or highly reflective surfaces. A typical image histogram shows a peak of slightly scattered, low values. Enhancement Remote Sensing

Contrast stretching is an expansion of the intensity levels used in visualizing the image to the entire range of usable intensity levels, by means of a linear or non-linear transformation. This is obtained using the so called Lookup Tables (LUT), an array of pairs of values that map the input values to the output levels of the display. The images very often contain a few very high values (clouds, small-highly-reflective surfaces, sensor errors), as well as few very dark values (shadows, non-reflective surfaces, sensor errors), thus generally the “tails” of the histogram that may contain anomalous values are not taken into account when building the stretch LUT. Enhancement

Remote Sensing pixel count Enhancement INPUTOUTPUT

Enhancement Remote Sensing

Enhancement Remote Sensing

Enhancement Remote Sensing