Natural ResourcesCanada

Ressources naturellesCanada

Canadian Space Agency

Agence spatiale canadienne

Power Point Presentation adapted by Claude Brun del Re

Geomatics for EducatorsGeomatics for Educators

Geomatics

• Term originally created in Canada • Geomatics is the science and technology of gathering,

analyzing, interpreting, distributing and using geographic information. Geomatics encompasses a broad range of disciplines that can be brought together to create a detailed but understandable picture of the physical world and our place in it. These disciplines include: – Mapping and Surveying– Geographic Information Systems (GIS)– Global Positioning System (GPS)– Remote Sensing

Canada’s Role in Geomatics• Canada exports ~ $300 million worth of geomatics products and services.• Growth rate of 15 to 20 per cent per year. • Demand for GIS products and services is expected to exceed $10 billion

per year.• Geomatics is one of the fastest-growing technology sectors and Canada is a

recognized leader, both in its development and in the provision of Geomatics software, hardware and value-added services.

• Natural Resources Canada- – Geomatics Canada

• Canada Centre for Remote Sensing• Centre for Topographic Information• Aeronautical Charts & Technical Services• Legal Surveys & International Boundary Commission• Geodetic Survey

List examples of remote sensing technology in your every day life

• Satellite weather maps

• Ultrasounds

• Speed radar

• Sonar (for ships, bats or dolphin)

• Photos

• CAT scans

• x-rays

REMOTE SENSING

• Definition and Process• Target• Sensor• Platforms• Electromagnetic

Energy• Interpretation• RADARSAT

Remote Sensing - A Definition

Indirect (remote) observations (sensing)

Remote sensing is the science (and to some extent, art) of acquiring image data and deriving information about the Earth’s surface without actually being in contact with it.

Remote sensing will give information about an object called

a target

Who could give me two common sensors?

Our eyes A camera

How does remote sensing work?Far away from the target, on what we call a platform.

Here are some types of platform

• Satellite

• Space shuttle

• Aircraft

• Balloon

• Ground base tower

Remote Sensing Process• Energy Source or Illumination (A)

• Radiation and the Atmosphere (B)

• Interaction with the Target or Surface (C)

• Recording of Energy by the Sensor (D)

• Transmission, Reception, and Processing (E)

• Interpretation and Analysis (F)

• Application (G)

Passive Sensor

• Passive sensors detect or “sense” reflected solar radiation

What does a passive sensor need

to sense the earth?

Active Sensors

• Active sensors produce and receive their own electromagnetic energy

They produce their own illumination and they

operate in the microwave region

Some Atmospheric Interactions

• Energy will interact with the atmosphere on its way in and out

• Ozone, nitrogen, CO2 and water vapour affect incoming energy

• Energy affected if wavelength is < or = the particle size

• Atmospheric windows are wavelengths not affected by the atmosphere

Absorption• Some substances absorb certain wavelengths of energy

• UV rays absorbed by ozone

•LW IR and SW microwaves absorbed by water vapour

•These wavelengths are not suitable for remote sensing

Scattering•Occurs when molecules are larger or equal to wavelength

•Rayleigh scattering - selective scattering (UV, Blue sky)

•Non-selective - scatters all visible wavelengths (clouds)

Atmospheric Windows

Terrain Interactions

• Radiation that reaches the Earth’s surface can be: Absorbed (A); Transmitted (T); and Reflected (R).

• This will vary with the type of object. The type of interaction will depend on the wavelength of the energy and the material and condition of the feature.

• Look at different objects, for example an egg, a green apple and a tomato.

Diffuse and Specular Reflectors

DiffuseDiffuse Specular Specular

rough surfacerough surface smooth surfacesmooth surface

Electromagnetic Energy• Electromagnetic energy is used to illuminate

the target in remote sensing

• Electromagnetic spectrum:Shorter wavelength Longer

wavelength

0.003nm 0.03nm 0.3nm 3nm 30nm 0.3 m 3 m 30 m 300 m 0.3cm 3cm 30cm 3m 30m

Gam

ma

Ray

X

-ray

Ult

ra-V

iole

t

Vis

ible

Infr

ared

Mic

row

ave

Rad

io

Visible Spectrum

Visible Wavelegths Violet: 0.4 - 0.446 m Blue: 0.446 - 0.500 m Green: 0.500 - 0.578 m Yellow: 0.578 - 0.592 m Orange: 0.592 - 0.620 m Red: 0.620 - 0.7 m

The basic colours of light

IR and Microwaves

Reflected IR: 0.72 m to 3.0 m

Thermal IR:3.0 m to 15 m

Microwaves:1 mm to 1 m

Visible / Infrared (VIR)

• Colours we perceive are combinations of electromagnetic energy

• VIR (visible infrared) or optical sensors capture energy reflected by targets in the optical and IR wavelengths

• Each target reflects or emits these types of energy in different amounts

Spectral Response

• Different objects reflect, absorb and transmit energy in differing amounts

• An object also transmits, reflects, and absorbs each wavelength differently

• Spectral responses enable us to identify different objects on images

• An object’s spectral response may change over time

Spectral Response - Leaves

• Chlorophyll absorbs red and blue

• Reflects green• Greenest in summer• Internal leaf structure

reflects near IR

Bands or Channels• Each sensor has a purpose (vegetation,

ocean, ice, weather)• Certain wavelengths provide more

information about certain targets• To perform their tasks, sensors on satellites

detect energy in very specific, narrow bands or channels of electromagnetic energy

Spatial Resolution

Fine ResolutionFine Resolution Coarse Resolution Coarse Resolution

Swath

• Total field of view

• Width of the image in ground distance

• For satellites, variesbetween 10s to 100sof kilometres

Orbits

• Geostationary Near-polar sun-synchronous

GOES• Geostationary Operational Environmental Satellite

• Operated by NOAA to for weather forecasting and monitoring

• 5 spectral bands (green-red to infrared)

• Geostationary above the equator at 75 degs E and W

• Resolution 1 to 4 kilometres

NOAA-AVHRR• Advanced Very High Resolution Radiometer

• Used for meteorology and other applications (vegetation) • Sun-synchronous, near-polar orbits

(830-870 km above the Earth)• Ensure that data for any region

of the Earth is no more than six hours old

• visible, near, mid infrared,

& thermal IR • 3000 km swath,

1 to 4 km resoloution

Landsat

• Landsat-1 was launched by NASA in 1972

• Landsat 7 was launched in 1999

• ETM (Enhanced Thematic Mapper) 8 bands VIR and Thermal IR

• 30 metre resolution

• 185 kilometre swath width

• Lots of archived data

• Near-polar, sun-synchronous orbits - 705 km

SPOT• Système Pour l’Observation de la Terre• French commercial satellites• SPOT 1 -1986• SPOT -2 operational, SPOT-4 just launched• Sun-synchronous, near-polar orbits at altitudes around 830 km• 2 Sensors MLA and PLA• PLA - black and white• MLA - 3 visible bands (blue-green-red)• 60 to 80 km swath• 10 to 20 m resolution

RADARSAT-1

• Canada’s first earth observation satellite

• Launched November 4, 1995

• Monitoring the Arctic (ice) is its main role

• Unique, flexible, “steerable” sensor

• Many swath width choices

• Many incidence angles available

RADARSAT-1Repeat Cycle

- 24 days

- 14 orbits per day

Coverage

- Global: 4,5 days

- North America: 3 days

- Arctic: daily

Altitude

- 798 km

Orbit Geometry

- Circular, Near polar

- Sun-synchronous

Inclination

- 98.6° (from the equator)

-Passes to the right of the North Pole

Period

- 100.7 Minutes

•

New Small Sats

• 1 to 5 metre resolution

• All commercially built

• IKONOS

• Earlybird

• QuickBird

RADAR

• RADAR is an acronym for RAdio Detection And Ranging

• A microwave (radio) signal is transmitted towards the target

• The sensor detects the reflected (or backscattered) portion of the signal

RADAR Images

• Radar images “look” like black and white photographs

• Tones of gray correspond to the amount of radar energythat is returned to the sensor

• The stronger the backscatter or the more energy that is returned to the sensor, thelighter that area or object will appear on the final image

RADAR Reflection

• There are three general types of reflection:

speculardiffuse corner

calm

Advantages

• Own energy source (images anytime of day)

• “Sees” through clouds (images anywhere)

• Provides good view of topography

• Sensitive to surface roughness

• Provides information on moisture content

Disadvantages

• Side-looking geometry creates distortions

• Radar speckle

• Excessive loss of data in mountainous areas due to shadows

Radar Sensors

• SEASAT - NASA 1978– lasted only a few months

• ERS-1 - ESA 1991-95– 30 metre resolution

• ERS-2 - ESA 1994– 30 metre resolution

• JERS-1 - Japan 1992– 18 metre resolution

What is an Image?• Image is a visual view of the energy reflected by the

target• Satellite images are digital: they are made up of numbers

usually from 0 to 255 where 0 is black and 255 is white• The numbers (radiance value) are arranged in rows and

columns• Each square is called a PIXEL• A number or a value of reflected energy is stored for

each pixel

Raster Data

• Images are stored as raster data - grid of cells or pixels

• Each pixel represents a certain amount of ground like 10 m x 10 m

• Each pixel is representative of the amount of energy backscattered by the target

Pixels and Lines

• Upper left corner is the origin

• X values are pixels or columns

• y values are lines or rows

Pixels and LinesPixels

Lines

X= Pixel 2 and Line 2 ( 2, 2)

X

Bits and Bytes

• Bits are binary digits (0 or 1)

• Images are collected as 8, 16, 32 bit data

• Bit refers to the number of exponential levels a binary digit is taken to– single bit = 21

– 8 bit = 28 or 256 levels of grey– 16 bit = 216 or 65536 levels of grey

Image File Formats

• .pix = PCI or Eoscape

• .img = ERDAS Imagine

• .lan = ERDAS

• GeoTIFF .tiff = contains georeferencing info

• TIF = requires header file for georeferencing

• .bil, ,bsq, raw = flat raster, common format, needs header file

• jpeg = common image format for the WWW, no georeferencing information

• GRID = ESRI raster format

VIR Images

• Usually 3 bands loaded

• One band loaded aloneappears as a greyscale

• Each assigned a colourgun (Blue, green, red)

• Together, 3 bands formcolour image