“ I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things so that he has a difficulty in laying his hands upon it. Now the skilful workman is very careful indeed as to what he takes into his brain-attic. He will have nothing but the tools which may help him in doing his work, but of these he has a large assortment, and all in the most perfect order.”

Sherlock Holmes < A. Conan Doyle , “A Study in Scarlet”>

“Give a man a fish, and he'll eat for a day. Teach him how to fish and he'll eat forever.” Chinese Proverb

Environmental Remote Sensing

Fundamentals of remote sensing• Definition

– "Remote sensing is the science (and to some extent, art) of acquiring information about the Earth's surface without actually being in contact with it. This is done by sensing and recording reflected or emitted energy

and processing, analyzing, and applying that information". • What remote sensing entails

– 1. Energy Source or Illumination (A)

– 2. Radiation and the Atmosphere (B)

– 3. Interaction with the Target (C)

– 4. Recording of Energy by the Sensor (D) -

– 5. Transmission, Reception, and Processing (E)

– 6. Interpretation and Analysis (F)

– 7.Application (G) -

Fundamentals of remote sensing

Electromagnetic radiation

The Electromagnetic Spectrum

Visible Violet: 0.4 - 0.446 mm Blue: 0.446 - 0.500 mm Green: 0.500 - 0.578 mm Yellow: 0.578 - 0.592 mm Orange: 0.592 - 0.620 mm Red: 0.620 - 0.7 mmInfraredReflected IR

- 0.7 mm to 3.0Thermal IR - the radiation emitted by the earth

- 3.0 mm to 100 mm.

Interactions with the Atmosphere • Scattering when the radiation is redirected

from its original path. – Rayleigh : particles are very small compared to

the wavelength

– Dominant scattering mechanism in the upper atmosphere. This is why the sky appears

"blue" . – Mie : particles are just about the same size as

the wavelength of the radiation. – Dominant in the lower portions of the

atmosphere where larger particles are more abundant,

– Optical: particles are much larger than the wavelength.

• 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.

– Carbon dioxide -> a greenhouse gas. It tends to absorb radiation strongly in the far infrared portion of the spectrum -

Passive versus Active • Passive sensors: measure energy that

is naturally available are called passive

sensors. • Active sensors: provide their own

energy source for illumination.

Satellite Characteristics: Orbits and Swaths

• Classification– ground instruments

– airborne instruments

– satellite instruments

• Satellite classification– geo-stationary

– polar-orbiting

Spatial Resolution, Pixel Size, and Scale

• Spatial resolution of– refers to the size of the

smallest possible feature that can be detected

• Pixel– the smallest unit of an

image

Weather Satellites/Sensors• GOES• 1 0.52 - 0.72 (visible) 1 km• cloud, pollution, and haze detection; severe

storm identification• 2 3.78 - 4.03 (shortwave IR) 4 km• identification of fog at night; discriminating water

clouds and snow or ice clouds during daytime; detecting fires and volcanoes; night time determination of sea surface temperatures

• 3 6.47 - 7.02 (upper level water vapor) 4 km• estimating regions of mid-level moisture content and

advection; tracking mid-level atmospheric motion

• 4 10.2 - 11.2 (longwave IR) 4 km

• identifying cloud-drift winds, severe storms, and heavy rainfall

• 5 11.5 - 12.5 (IR window sensitive to water vapour) 4 km

• identification of low-level moisture determination of sea surface temperature; detection of airborne dust and volcanic ash

Land Observation Satellites/Sensors• TM 1 0.45 - 0.52 (blue)

• soil/vegetation discrimination; bathymetry/coastal mapping; cultural/urban feature identification

• TM 2 0.52 - 0.60 (green)

• green vegetation mapping (measures reflectance peak); cultural/urban feature identification

• TM 3 0.63 - 0.69 (red)

• vegetated vs. non-vegetated and plant species discrimination (plant chlorophyll absorption); cultural/urban feature identification

• TM 4 0.76 - 0.90 (near IR)

• identification of plant/vegetation types, health, and biomass content; water body delineation; soil moisture

• TM 5 1.55 - 1.75 (short wave IR)

• sensitive to moisture in soil and vegetation; discriminating snow and cloud-covered areas

• TM 6 10.4 - 12.5 (thermal IR) vegetation stress and soil moisture discrimination related to thermal radiation; thermal mapping (urban water)

• TM 7 2.08 - 2.35 (short wave IR)

• discrimination of mineral and rock types; sensitive to vegetation moisture content

Applications• Agriculture

– crop monitoring: grain supplies forecasting (yield prediction), crop production statistics, crop rotation records, mapping soil productivity, identification of factors influencing crop stress, assessment of crop damage due to storms and drought, and monitoring farming activity.

• Hydrology– flood detection: quick calculations and

assessments of water levels, damage, and areas facing potential flood danger. Users of this type of data include flood forecast agencies, hydropower companies, conservation authorities, city planning and emergency response departments, and insurance companies (for flood compensation). Important for planning and transportation routing

– soil moisture: hydrologic forecasting

Applications (ctd.)• Ocean color and phytoplankton analysis:

– Indicates the "health" of the ocean, by measuring oceanic biological activity by optical means . Phytoplankton, are significant building blocks in the world's food chain and grow with the assistance of sunlight and the pigment chlorophyll. Chlorophyll, which absorbs red light (resulting in the ocean's blue-green colour) is a good indicator of the health of the ocean and its level of productivity.

– Mapping and understanding changes in ocean colour can assist in the management of fish stocks and other aquatic life, help define harvest quotas, monitor the water quality and allow for the identification of human and natural water pollution such as oil or algal blooms, which are dangerous to fish farms and other shell fish industries.

• Oil spills– Spill location– Size and extent of the spill – Direction and magnitude of oil movement – Wind, current and wave information for predicting

future oil movement

Applications (ctd.)

• Climate modeling and assessment– 1/3 of the total solar energy contributes to evaporation. Better accuracy in

rainfall estimation greatly enhances our understanding of the interactions between the sea, air and land masses which produce changes in global rainfall and climate.