1. Introduction to Remote Sensing
Resolution
Digital Images
Image Interpretation
Satellites and Sensors

2. Remotes Sensing Technology
Remote Sensing Images can be obtained from:
Aerial Photographs
Contract a company to take the aerial photographs
Obtain from local Property Appraiser’s Office
Obtain from USGS
Satellite Images
There are a number of countries that operate satellites that collect images of the Earth for commercial purposes
LANDSAT is operated by the United States

3. Digital Images A digital image can be broken down
layers (or CHANNELS or BANDS) representing different types of light
each layer is black and white,
combination of three channels result in a color image
into a regular grid of PICTURE ELEMENTS or PIXELS
Look carefully at you computer monitor: it is made up of a grid of dots just like a digital image.

4. Digital Images
An aerial photograph or satellite image has three different resolutions
The SPATIAL resolution
The SPECTRAL resolution
The RADIOMETRIC resolution
The TEMPORAL resolution

5. Resolution & Remote Sensing Systems
4 major resolutions associated with each remote sensing system
Spectral resolution
Spatial resolution
Temporal resolution
Radiometric resolution
These resolutions should be understood by the scientist in order to extract meaningful biophysical or hybrid information from remotely sensed imagery.

6. Resolution Resolving power
Measure of the ability of a sensor to distinguish between signals that are spatially near or spectrally similar

7. Spectral Resolution
Number and size of the bands which can be recorded by the sensor – nominal spectral resolution
Course – sensitive to large portion of ems contained in a small number of wide bands
Fine – sensitive to same portion of ems but have many small bands
Goal – finer spectral sampling to distinguish between scene objects and features
More detailed information about how individual features reflect or emit em energy increase probability of finding unique characteristics that enable a feature to be distinguished from other features.
Number and dimension of specific wavelength intervals of ems to which rs instrument is sensitive.

8. Spectral Resolution
Difficult to create detector that has extremely sharp bandpass boundaries such as describe in previous slide
More precise method of stating bandwidth is look at typical Gaussian-shape of the detector sensitivity
Describe bandwidth as Full Width at Half Maximum (FWHW)

9. Spectral Resolution
The SPECTRAL resolution defines the range of light stored in the image
A black and white photograph stores a visible light; it has one channel that stores the light for 0.4 to 0.7 micrometers
A natural color image stores reflected red, blue and green light in different channels; e.g mm for blue, mm for green and mm for red
A LANDSAT image contains 7 channnels as described above that store reflected light other than visible light.
A HYPERSPECTRAL image contains hundreds of channels. E.g. A hyperspectral image that collects visible light may divide the visible light range into 300 channels, each channel containing a narrow range of wavelengths.

10. Spatial Resolution
Measure of the smallest angular or linear separation between 2 objects that can be resolved by the sensor
In practice, sensor system’s nominal spatial resolution is the dimension in meters (or feet) on the ground projected instantaneous field of view (IFOV)
Generally, smaller spatial resolution  greater the resolving power of the sensor system
Relationship between size of a feature to be identifed and spatial resolution of rs system
Satellite systems operate in fixed orbits with fixed optical systems that have a constant IFOV in comparison to aerial photography.
Add graphic showing satellite and FOV/IFOV
SPOT panchromatic band – 10x10m
Landsat TM – 30x30m
Landsat MSS – 79x79m
NOAA AVHRR – 1km
GOES Imager 1-4km

11. Spatial Resolution
The SPATIAL resolution defines that size of Earth’s surface that is stored in a pixel
In a LANDSAT image a pixel represents 30 m by 30 m of the Earth’s surface.
In an USGS orthophotograph a pixel repesents 1 m by 1 m of the Earth’s surface.

12. Graphic representation showing differences in spatial resolution among some well known sensors
Add SSM/I, GOES Imager, NOAA AVHRR
(Source: Landsat 7 Science Data Users Handbook)

14. Spatial Resolution
Useful rule: To detect a feature, the spatial resolution of the sensor system should be less than ½ the size of the feature measured in its smallest dimension.

15. Temporal Resolution
How often the remote sensing system records imagery of a particular area.

16. Radiometric Resolution
26 = (0-63) 64
28 = (0-255) 256
210 = (0-1023) 1024
Examples:
GOES Imager – 10bit
Landsat 7 ETM+ - 8bit
Refers to the sensitivity of the sensor to incoming radiance.
How much change in radiance must there before a change in recorded brightness value takes place.
This sensitivity to different signal levels will determine the total number of values that can be generated by the sensor
? Check Landsat7 ETM+
Modis

17. Radiometric Resolution
The RADIOMETRIC resolution defines the range of values that an individual pixel can have
Typical digital images have a range of values from 0 – 255 (a total of 256 possible values).
An image that just shows black or white pixels would only store 0 (black) or 1 (white).
Consider if you had 100 light bulbs of unknown and different wattages and you had to put them into four boxes: very bright, bright, dull, very dull. Your radiometric resolution is 4. The LANDSAT satellite is capable of characterizing reflected light into 256 level of brightness in addition to the seven types of wavelengths.

18. Summary of Resolution
By increasing 1 or any combination of these resolutions, increase chance of obtaining remotely sensed data about a target that contains accurate, realistic, and useful information.
Downside of increased resolution  need for increased storage space, more powerful processing tools, more highly trained individuals.

19. Aerial Photography Types depend on: the altitude of the plane
the camera
the angle of view and
the type of film used

20. Vertical (directly over) Oblique (at an angle)
The angle of view
Vertical (directly over)
shows the scale and distance
Oblique (at an angle)
shows the object size

21. A Vertical Aerial Photograph

22. An oblique photograph

23. beyond the visible part of the spectrum
Photographic films
Black and White
Color
InfraRed
beyond the visible part of the spectrum

24. Monochrome (black and white)

25. Panchromatic
(color)

26. Color Infrared (heat) Used for vegetation studies
Green vegetation strongly reflects IR
Vigorously growing vegetation appears red

27. Image Interpretation Size of objects Shape Image tone Patterns
relative to one another
Shape
depends on the object outline
Image tone
brightness - hue, colour
Patterns
arrangement of features

28. Image Interpretation Texture smooth or coarse Shadow
helps determine heights
Site
location helps recognition
Association
features that are normally found near others

29. Interpretation

30. Difficulties with Interpretation
unfamiliar prospective
viewing from above
use of wavelengths outside visible light range
Images often display different types of infrared light
Colors in image not that same as colors seen by us
E.g. False infrared images displayed reflect near infrared light using red
unfamiliar scales and resolution
Landsat image’s pixels are 30 m by 30 m
SPOT image’s pixels are 20 m by 20 m
Aerial photograph’s pixels can be smaller than 6inches

31. Characteristics of Objects
Shape
the general form of the object
stereo photographs also show height which further defines shape
The image is of the Pentagon, easily recognizable by its shape

32. Characteristics of Objects
Size
this needs to be considered in reference to scale
What is the object in the image
The image covers approx 1 square mile?
The image is of one of the Launch sites at Cape Canaveral.

33. Characteristics of Objects
Pattern
this is the spatial arrangement of objects
e.g. Orchard vs. Forest
Man made objects vs. natural objects
The image shows part of Washington DC.

34. Characteristics of Objects
Tone (Hue)
the relative brightness of an object or its color
This image is of a part of West Brevard county, south of Lake Washington. The dark area to the upper left is water. Much of the rest of the image is swap land with variations in vegetation.

35. Characteristics of Objects
Texture
frequency of tonal changes
e.g. grass appears ‘smoother’ than forest
depends on scale
The images are different ‘zoom’ levels showing more detail (less texture) when zoomed in.

36. Characteristics of Objects
Shadows are both useful and a nuisance
define the profile of the object
hide objects in the shadow area
The shadow here helps identify the Washington Monument.

37. Characteristics of Objects
Site
topographical location
e.g. palm trees are not found in New England
Association
what objects are found together
e.g. a Ferris wheel
The image displays the Mall in Washington DC with the Washington Monument at the center.

38. Strategies Other information in addition to the image
e.g. for crop identification use information on typical planting dates, recent weather conditions etc
Russian wheat is planted in the late Fall, before the snow Falls. It is protected from the extreme cold by the layer of snow during the winter months. Back in the late 70’s/early 80’s there was a prediction of massive wheat shortages in Russia months before the wheat ever started to grow. Satellite images had shown that large parts of Russia had no snow cover: the wheat seed would never germinate.

39. Strategies There are two types of Interpretation keys.
Selective keys provide a set of example images.
E.g. pictures of different trees from above
Elimination keys makes the interpreter make a series of decision.
Is the ‘crown’ of the tree large or small: small might suggest pine tree in a given location rather than oak trees.
better for man made objects rather than vegetation.

40. Strategies Consider film / filter combinations (or sensor channels)
Would a false infra red image be better than a natural color image?
Consider the Arial extent of the photograph
Do you need to have great detail or large aerial coverage?

41. Approaching Classification
Define the classifications.
What objects are you trying to identify in the image
What objects are considered the same
Pine tree forest and oak tree forest considered as just forest?
‘fuzzy’ edges,
Try to give good definition of where boundaries lie between natural objects
E.g. where desert ends and non-desert starts

42. What is a satellite?
The term Satellite simply refers to a body in orbit around another body.
In 1957 the first artificial satellite SPUTNIK, was launched by the Soviet Union. Today there are hundreds of these spacecraft in orbit around the Earth.
Satellites may serve many different purposes; they may be part of a television or telephone network or they can carry instruments to investigate the Earth’s surface or the Earth’s atmosphere.
Other spacecraft point towards the Sun and monitor this star, or travel for many years carrying probes or landers which investigate the atmosphere, moons or surface features of distant planets.
There are also manned spacecraft such as the US shuttle spacecraft and space stations such as MIR, the Soviet space station launched in 1986.

43. Satellite Orbits
Satellites generally have either polar orbits or geostationary orbits.

44. Meteosat
A program sponsored by 17 European weather services. It started with the successful launch of METEOSAT 1 in 1977 and has continued unabated. METEOSAT 7, the last in the current series was launched in early September 1997.
They are stationed above the equator at 0° longitude above the Gulf of Guinea and image this part of the globe every 30 minutes in three wavebands. These are:
the visible (0.4 to 1.1 micrometers),
the water vapour (5.7 to 7.1 micrometers) and
the thermal infrared (10.5 to 12.5 micrometers).
The first has a resolution of 2.5 km The first has a resolution of 2.5 km at the sub-satellite point (SSP) while the two infrared wavebands both have one of 5 km.

45. NOAA (National Oceanic & Atmospheric Administration) Polar Orbiters
The programme that started with the successful launch of TIROS-1 in 1960 continues today with the NOAA polar orbiters. The satellites' AVHRR instruments image the planet in five bands:
8 to 0.68 micrometres
0.725 to 1.10 micrometres
3.55 to 3.93 micrometres
10.30 to micrometres
11.50 to micrometres

46. Geostationary Operational Environmental Satellites (GOES)
This NOAA series of geostationary weather satellites began in 1974 and continues today with the launch of a new ‘GOES-NEXT series of more advanced satellites in 1994.
The resolution varies from 4 to 8 km.
They have five wavebands:
0.55 to 0.75micrometres
3.80 to ”
6.50 to 7.00 “
10.20 to ”
11.50 to "

47. The Space Shuttle
The space shuttle is a manned spacecraft mission, carrying astronauts and scientists as well as instruments.
The most important sensors that have been carried on the Shuttle for Earth imaging are:
The Shuttle Imaging Radar
The Metric Camera.
The Large Format Camera (LFC)
The Modular Optical-Electronic Multispectral Scanner (MOMS).

48. LANDSAT Satellite Series
First LANDSAT satellite launched in 1972
Lasted until 1978
Six Landsat satellites to date
LANDSAT-4 and -5 still operational
LANDSAT -6 experienced launch failure
LANDSAT series of satellites were built in the US and launched by NASA. Other important ‘Earth Mapping’ satellites in orbit include the French SPOT satellites, the Indian IRS satellites, Canadian RADARSAT, the European ERS satellites and the Japanese JERS satellite.

49. Technical Information
Landsat 4 (launched )
Landsat 5 (launched )
Orbit
near polar sun-synchronous
complete orbit every 99 mins
Altitude km, 438 miles
Re-visit days

50. Landsat 1, 2 and 3
Landsat was the first satellite to be designed specifically for observing the Earth’s surface.
Landsat 1, 2 and 3 carried a multispectral scanner (MSS) system which records reflected energy from the Earth’s surface or atmosphere across four wavebands; three visible channels and one near infrared.
The MSS has a pixel resolution of 80 metres.

51. Landsats 4 & 5 - Thematic Mapper
LANDSATs 4 and 5 have a more refined multispectral scanner, the Thematic Mapper (TM), instrument on board.
TM is a multispectral sensor since it detects energy across seven wavelength bands.
The pixel resolution of six of the wavelength bands is 30 metres but the thermal infrared band has a pixel resolution of 120 metres.
On this Landsat TM true colour image of west and central London

52. Landsat 7
After a successful launch on April , Landsat 7 is up and running. Visit to see "Quick Looks" of some of the first acquired images..
LANDSAT 7 carries a TM sensor developed from that on Landsat 5. Key differences are: (1) extra 15m panchromatic band co-registered with the multi-spectral, and (2) band 6 resolution at 60m.
The fires of Dili, east Timor
The Turkish earthquake

53. LANDSAT’s Thematic Mapper Sensor
Collect 7 different types of light
mm blue R
mm green R
mm red R
mm near IR R
mm mid IR R
mm thermal IR E
mm mid IR R and E
Note the range of light for each of the different ‘channels’.

54. Technical Information
Payload
MSS (4 channels)
TM (7 channels)
Resolution
MSS 80 m
TM 30 m (band 6, 120 m)
Swath
185 km x 185 km

55. Applications of LandSat Imagery
Geology
surveys for oil and mineral exploration
Agriculture
crop monitoring / yield forecast
Cartography
large area maps, to 1:50,000
Environment
environmental audits and pollution monitoring
Forestry
woodland mapping / species identification

56. Applications of LANDSAT Imagery
Planning
land use analysis and change detection
Utilities
highway / power / resource management
Commerce
insurance damage assessment, civil engineering and commodities forecasting
Marine
coastal zone management and bathymetric mapping

57. SPOT (Systeme Probatoire de l’Observation de la Terre)
SPOT satellites are placed in near-polar, sun-synchronous orbits at an altitude of 832 km.
The satellites have a pushbroom scanner system which can view the surface immediately below them (nadir view), or can be directed so that they view the surface to the side. This is important because it means that two views of the same area can be collected within a short time of each other, by two adjacent over-passes. Because the system can take two images of the same area with different look angles, it is possible to create stereoscopic (3-D) images. This is similar to having two eyes, enabling us to view in three dimensions because each eye views the same scene from a slightly different position, the brain then creates a 3-D picture.
A computer can create a Digital Elevation Model (DEM) from two stereoscopic images, which means the shape of the land can be measured.

58. SPOT Images with two different spatial resolutions can
be produced from SPOT data. The first is a panchromatic (black and white) image with a spatial resolution of 10 m. The second is an image from the multi-spectral sensor (SPOT XS) which collects 3 bands of data, with a resolution of 20 m.

59. Active Sensors: ERS-1 and ERS-2
In July 1991, the first European Remote Sensing Satellite (ERS-1) was launched by the European Space Agency (ESA). It had a sun-synchronous circular orbit (near polar) at 770 km. Its purpose was to collect information on areas of the world that are difficult to observe from the surface, such as oceans and ice-covered areas. It also produces images of the land surface in all weather conditions, 24 hours a day.
ERS-1 was so successful that the ERS-2 was launched in April 1995, carrying additional equipment called Global Ozone Monitoring Experiment (GOME).

60. Active Sensors: Radarsat
RADARSAT-1 spacecraft was launched in November 1995, by the Canadian Space Agency. The satellite carries a Synthetic Aperture Radar system providing all-weather, day and night observations of land and sea surfaces.The satellite’s SAR system has been designed to make it useful for a range of applications including:
crop investigations
coastal zone mapping
ship detection
hydrological applications
geological applications
ice monitoring
oil spill detection
ocean applications
e.g. mapping the ocean depths/shape of the sea floor)