dirty remote sensing - wordpress.com · 2015. 1. 30. · • role of the atmosphere. all energy...
TRANSCRIPT
Purpose
Give you a very basic skill set and softwaretraining so you can find free image data,process and analyse in order to produce aclassified habitat map
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5 weeks• Week1- Introduction & and how to find
images
• Week2- How to interpret Images
• Week3- How to assess & process imagesbefore use
• Week 4- How to classify and image tomake a map
• Week 5 – How to validate and improveyour map
Software
• ArcGIS & Multispec- both free, downloadand use on your own computer
• https://engineering.purdue.edu/~biehl/MultiSpec/
• http://www.esri.com/software/arcgis/explorer
• http://www.seos-project.eu/modules/agriculture/agriculture-c00-p01.html
• www.ag.ndsu.edu/pubs/ageng/gis/ae1262.pdf
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• 10-11 Lecture
• 11-12- Practical group 1
• 12-1 Practical group 2
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• Basically we will look at how the images wesee on google earth are made and how we canconvert them from a web-toy to serious piecesof analytical kit.
• Remember this “Remote sensing technology”is a multi billion industry that supports trillionsof spending from agriculture to the military,from real estate to mining.
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http://googlesightseeing.com/
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Remote Sensingis What?
“The science of tellingsomething about anobject without touching it”
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• It’s the use of images taken from above,to tell us about the world.
• We are all used to these images now
• Google earth is a great example but alsoweather forecasting – Evelyn Cussak etal show us satellite pictures every day
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What benefits does RS bring
• Wide overview
• Complete access
• Repeatability
• A different perspective
• http://staff.aub.edu.lb/~webeco/rs%20lectures.htm
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High Resolution Imagery
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What benefits does RS bring
• Wide overview
• Complete access
• Repeatability
• A different perspective
• http://staff.aub.edu.lb/~webeco/rs%20lectures.htm
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What benefits does RS bring
• Wide overview
• Complete access
• Repeatability & timeliness
• A different perspective
• http://staff.aub.edu.lb/~webeco/rs%20lectures.htm
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What benefits does RS bring
• Wide overview
• Complete access
• Repeatability & timeliness
• A different perspective
• http://staff.aub.edu.lb/~webeco/rs%20lectures.htm
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In short
• A new perspective
• Information that’s not available in otherways
• A synoptic view
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Remote sensing is used routinelyin these areas
• Agronometrics
• Environmental resource mapping
• Policy monitoring/evaluation
• Landuse issues
• Pollution control
• Hazard mapping
• Disaster reflief
• Policy development
• Planning
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Some examples from my lab, some ofwhich we’ll see in more detail later
• A hedgerow map from aerial photography
• Maps of landcover from satellites
• Measuring grass growth from satellites
• Identifying High Nature Value Farms with GIS&RS
• Measuring economic impact of environmental legislation onfarming using GIS
• Measuring 3D biomass with laser scanners
• Phenology from multi-temporal low res satellites
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Habitat Maps: Teagasc.
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The Physics of Light
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• We will look at different remote sensingtechnologies over the coming weeks but,for now, just image all we will be doingfor the next few lectures is looking atphotographs!
• But how are photographs, either film ordigital, formed?
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Taking a Picture from Space
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We Rely upon
Electromagnetic Energy
• We are all familiar with EMR (even if wedon’t realise it!)
• Light, radio, microwaves – are all EMRand part of the ElectromagneticSpectrum
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The spectrum
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Properties of EMR
EMR can be thought of as little packets, orquanta, or Energy called Photons
Or as energy propagating as a wave
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Psst..dont mention this to any physics heads but..
You can chose to think of light as either model:
• The machine gun model: Image the sun (or a laser pointer or alamp) firing out little packets of energy that shoot through the skyand bounce of, or through or are scattered by objects
Or
• The radio model: Imagine the sun broadcasting waves of energylike a radio antenna that reflect, or transmit or are diffracted byobjects
In both cases the amount of energy is determined by thewavelength
of the light involved and we can only see stuff because some of that
energy is bounced or reflected of an object into our eyes (or our
camera or our satellite imaging device)
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E=n.h
1E
E is energy,measured in Joulesand λ is wavelengthmeasured in meters
C speed measured inmeters per second
n frequency measuredin Hertzλ wavelength measuredin meters
C=l.n
All Electromagnetic radiation(EMR) travels at the speed of light
E is energy,measured in Joulesand h is Planksconstant
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• Wave length is measured in nanometers nm
• Blue light has a wave length of ~450nm
• Green ~550nm
• Red ~700nm
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Absorption (A) occurswhen radiation(energy) is absorbedinto the target whiletransmission (T)occurs when radiationpasses through atarget. Reflection (R)occurs when radiation"bounces" off thetarget and isredirected. In remotesensing, we are mostinterested inmeasuring theradiation reflectedfrom targets.
What happens when a photon meets an object?
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Spectral Properties of Objects
• “Everything in nature has it’s own unique distribution of reflected,emitted and absorbed radiation. These spectral characteristics can– if ingeniously exploited- be used to distinguish one thing fromanother or to obtain information about shape, size, and other
physical and chemical properties”
(Parker and Wolf, 1965, p21).
Colour!
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Color as Light (Spectral Color)The Electromagnetic spectrum consists of the spectral hues of light. Hue is thespecific color, identified by a name, (e.g., red, blue, green, etc.) as they are the
component wavelengths of white light.When combined together in equalamounts, they form white light. Color as Light is translucent, that is, we can see
through the colors and can project colors over one another to form other colors
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Reflected ColorMost surfaces are opaque (not transparent).These surfaces absorb andreflect different amounts of color from white light. Most of the colored
objects we see on earth are made up of combinations of reflectedwavelengths. Surfaces or objects illuminated by white light absorb
differing proportions of visible wavelengths and reflect the remainder.
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Bet you didn’t realise you’d be doingquantum mechanics…
Before we go any further we need to mention that theseprocesses are generally quantised (not always so in thecase of scattering).
What this means is that the processes occur a fixed discreteenergy levels. In the macro world we live in filling a jug withwater is a non-quantised process. If you need to fill a litrejug, then you can poor 100ml, then 50 then 600 and then therest in order to fill the jug or if you have a 2l Jug you can poorhalf in to fill your 1l jug.In a quantised world you can only fill a 1l jug with water fromanother 1 l jug in one go – you can’t use small amounts tomake up the total and you can’t use just some of a biggeramount.
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KEY CONCEPTS OF REMOTE SENSING.• Spectral Differentiation.• Remote sensing depends on observed spectral differences in the energy
reflected or emitted from features of interest.• Radiometric Differentiation.• Remote sensing also depends on the ability to determine differences in the
brightness of objects and features..• Spatial Differentiation.• Every sensor is limited in respect to the size of the smallest area that can be
separately recorded as an entity on an image.• Geometric Transformation.• Remote sensing does not immediately produce images with accurate,
consistent geometric relationships between points on the ground and theircorresponding representations on the image.
• Role of the Atmosphere.All energy reaching the remote sensing instrument must pass through aportion of the earth’s atmosphere. In doing so, the sun’s energy is altered inintensity and wavelength by particles and gases in the earth’s atmosphere.These changes appear on the image in ways that degrade image quality orinfluence the accuracy of interpretations.
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What Is A Digital Image?
72808492979485787581
72707478859397888179
71616770768290979387
727479777579798910396
4459778785848897110105
563951839195101100104104
7558435684106106938693
78797541406587867988
78828672453244698280
85858684775938457779
87918881858464415370Pixel
What you see…What your computer sees…
Digital Number (DN) Digital numbers (DNs)typically range from 0 to255; 0 to 511; 0 to 1023,etc. These ranges arebinary scales: 28=256;29=512; 210=1024.
MERMS 12 - L4
MERMS 12 - L4
What Is A Digital Image?
72808492979485787581
72707478859397888179
71616770768290979387
727479777579798910396
4459778785848897110105
563951839195101100104104
7558435684106106938693
78797541406587867988
78828672453244698280
85858684775938457779
87918881858464415370
72808492979485787581
72707478859397888179
71616770768290979387
727479777579798910396
4459778785848897110105
563951839195101100104104
7558435684106106938693
78797541406587867988
78828672453244698280
85858684775938457779
87918881858464415370
72808492979485787581
72707478859397888179
71616770768290979387
727479777579798910396
4459778785848897110105
563951839195101100104104
7558435684106106938693
78797541406587867988
78828672453244698280
85858684775938457779
87918881858464415370
columns (x)
row
s(y
)
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Greyscale vs. RGBGreyscale is typically used to display a single band…
…while RGB (“Red”, “Green”, “Blue”) images can display 3 bands, corresponding to the red, green andblue phosphors on a monitor. Computer monitor colors are additive, meaning “true” red + green + blue= white.
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Data Visualization
• A digital number in a satellite image has no intrinsicvisual display meaning to the computer.
• Based on some predefined algorithm, the computeradjusts the brightness on the screenas a function of thepixel value. This function can take a wide range offorms.
• Typically, lower pixel values are displayed as “dark” andhigher pixel values are displayed as “bright”.
• Important to remember: while there is no limit to thenumber of image bands, there is a limit to the number amonitor can display at once.
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Finding sources of satelliteinformation
• http://sirius.spotimage.com/PageSearch.aspx
• http://geofuse.geoeye.com/maps/Map.aspx
• http://www.resmap.com/imagery.aspx
• http://glovis.usgs.gov/
• http://landsatlook.usgs.gov/viewer.html
• https://earthdata.nasa.gov/labs/worldview/• https://earthdata.nasa.gov/data/data-tools/search-and-order-tools
• http://www.gis4biologists.info/free_satellite_images.htm
• http://earthexplorer.usgs.gov/
• http://www.flashearth.com/
• http://earthexplorer.usgs.gov/
• http://glovis.usgs.gov/
• http://reverb.echo.nasa.gov/reverb/#utf8=%E2%9C%93&spatial_map=satellite&spatial_type=rectangle
• https://earthdata.nasa.gov/labs/worldview/
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Practical
• Find the Lat/Long of your place of birth (POB)
• Go to the GLOVIS satellite web site
• Find a Landsat 8 image for your area, and ADDscene to list
• Click send to cart then register for an account
• Process your scene- you will get an emailconfirming your image is ready for download.
• Select the Natural look image and download.
• Examine the image