Final Exam Lecture Flashcards
Why use remote sensing?9
- a regional view (in general), even a local view now a
days. - repetitive looks at the same area
- “see” over a broader portion of the spectrum than the human eye
- Remote sensors often record signals electronically
and provide geo-referenced digital data - Sensors can use a very specific bandwidth for imaging
- They can also use a number of bandwidths
simultaneously - Some remote sensors operate in all seasons, at night,
and in bad weather - Images are permanent record (fixed in time)
- Often more accurate source of historical information
What elements are involved in remote sensing?General 5
• EM Energy • Atmosphere • Objects • Satellite system -Use of energy source -Use of energy bands -Data acquisition approach -Capture -Storage and archive -Distribution • Data processing and analysis methodology -Visual -Digital
___ radiation is the carrier of electro-magnetic energy by transmitting the
oscillation of the electric and magnetic fields through space or matter.
EM radiation is the carrier of electro-magnetic energy by transmitting the
oscillation of the electric and magnetic fields through space or matter.
The spectral sensitivity of the human eye(visible light) is from about . to _._which is termed as visible
wavelength of EM spectrum.
0.4-0.7
4 basic rules of wave theory
Ex:Assume the speed of light to be 3x10(8) m/s. If the
frequency of an electromagnetic wave is 500,000 GHz
(GHz = gigahertz = 109 m/s), what is the wavelength of
that radiation?
-give answer in micrometers,nanometers, and centimeters
1.. Electromagnetic radiation consists of
a. an electrical field (E), which
varies in magnitude in a direction
perpendicular to the direction in
which the radiation is traveling,
and
b. a magnetic field (M) oriented at
right angles to the electrical field.
Both these fields travel at the
speed of light (c).
2.The wavelength is the length of one wave cycle, which can be measured as the distance between successive wave crests -A wavelength is usually represented by the Greek letter lambda (λ). Wavelength is measured in metres (m) or some factor of metres such as nanometres (nm, 10-9 metres), micrometres (μm, 10-6 metres) or centimetres (cm, 10-2 metres).
- Frequency refers to the number of cycles of a wave passing a fixed point per unit of time.
-Frequency is normally measured
in hertz (Hz), equivalent to one
cycle per second, and various
multiples of hertz.
4. Wavelength and frequency are related by the following formula: λν=c where λ is the wavelength, ν is the frequency and c is the speed of light.
Ex:Assume the speed of light to be 3x10(8) m/s. If the
frequency of an electromagnetic wave is 500,000 GHz
(GHz = gigahertz = 109 m/s), what is the wavelength of
that radiation?
(3x108 m/s)/(500,000,000,000,000)
=6x10(7) meters
=6x10(13) micrometers
______ the wavelength the _____ the frequency
shorter,higher
______ the frequency the _____ the wavelength
lower,longer
_____ light is most easily absorbed by atmos
visible
-becomes innacurate after
Role of atmos in remote sensing: 4
The sunlight’s transmission through the atmosphere is affected by absorption and scattering of atmospheric
molecules and aerosols.
Similarly, the reflected and emitted energy that is
received by a satellite sensor are also modified by the
atmospheric molecules and aerosols.
3 types of Scattering of EM by the Atmospheric elements
- Rayleigh scattering: occurs when the particles (gas
molecule) causing the scattering are significantly smaller than the wavelengths being affected.
• Blue Sky & Red Evening light - Mie scattering: the particles (dust or smoke) causing the scattering are roughly the same diameter as the
wavelengths they’re scattering. - Nonselective scattering: what’s (water droplets)
causing the scattering is larger than the wavelengths
being scattered.
• all wavelengths equally; explains why we see clouds as white if it is not much thick
3 interactions of EM with Earth Surface objects
reflected (R),
absorbed (A) or
transmitted (T)
2 types of light that are reflected from vegetation
Infrared and Green
EM interaction with water
What is there is suspended sediment?
longer wavelengths-more absorption by water
blue-is the most reflected by water
-means higher reflectivity in all bands
4 Main Classes of visible wavelength and μm
• blue is about 0.4 to 0.5 μm
• green is about 0.5 to 0.6 μm
• red is about 0.6 to 0.7 μm
Near infrared: 0.8-0.9
Describe Wavelengths for each? Clear Lake Water: Turbid river Water: Vegetation: Dry Soil: Wet Soil:
Clear Lake Water:lower reflectance than turbid
Turbid river Water: higher reflectance than clear, lasts into longer wavlengths
Vegetation: minimal reflection up until around 0.5-0.6(green) then goes down and increases to maximum at near infrared and infrared (0.8 up)
Dry Soil:much higher reflectance than wet
Wet Soil:
Microwave wavelength: can be used at…
any time of day or night
Infrared energy is the heat coming out of a vegetation
-________ the vegetation, the more Heat Energy coming off of it
Infrared energy is the heat coming out of a vegetation
-HEALTHIER the vegetation, the more Heat Energy coming off of it
ultra blue band(lower than blue) is useful for
Two thermal bands 10 and
11 are useful iTwo thermal bands 10 and
11 are useful in ….
New band 1 (ultra-blue) is useful for coastal and aerosol studies
Two thermal bands 10 and
11 are useful in providing
more accurate surface
temperatures.
Spatial resolution of:
___ meters (visible, NIR, SWIR);
___ meters (thermal);
and ___ meters (panchromatic).
30,100,15
Principal Applications of Blue, Greeen, Red, Near Infrared
- 0.45-0.52. Blue. Water body penetration makes this band useful for coastal water mapping. Also useful for soil/vegetation discrimination, forest type mapping, and cultural feature identification.
- 0.52-0.60. Green. Suitable for measuring the green reflectance peak of vegetation for vegetation discrimination and vigor assessment. Also useful for cultural feature identification.
- 0.63-0.69. Red. A chlorophyll absorption region aids in plant species differentiation. Also useful for cultural feature identification.
- 0.76-0.90. Near-infrared. Useful for determining vegetation types, vigor, and biomass content, for delineating water bodies, and for soil moisture discrimination.
________ data: when you have many bands within your study
Hyperspectral
______ clouds: interceptor of all the signals in and out
cirrus
to delineate between water/moisture level what is the best em to use?
infrared
If you wanted to map the deciduous (e.g. maple, birch) and the coniferous (e.g. pine, fir, spruce) trees in a forest in summer using remote sensing data, what would be the best way to go about this and why?
- Infrared-because there is the biggest deviation
- deciduous trees reflect alot more then coniferous
_______ trees reflect less than ________ trees in infrared
coniferous
deciduous
Image Pixel value:grayscale
Black=
gray=
White=
0
127
255
need to ______ pixels if using data from different satellite types
coregister
. Remote sensing uses _______ colour system
. when printing a map it is ______ colour system
. Remote sensing uses Additive colour system
-when printing a map it is Subtractive colour system
False colour composite
Blue Gun:
Green Gun:
Red Gun:
Blue Gun:Green
Green Gun:Red
Red Gun:near-Infrared
Normalized Difference Vegetation Index
Normalized Difference Vegetation Index
(NDVI) = (NIR - Red)/
(NIR + Red)
ex:
(0.50-0.08)/(0.50+0.08)
=0.72
ex:
(0.40-0.30)/(0.40+0.30)
=0.14
Image Classification
Digital Classification
Image classification is the process of categorization of all image pixels into land cover classes to produce a thematic representation of the image.
Digital classification is a the process of recognising patterns in the image pixel values in one or multiple bands and assign them to one of the land cover classes.
Patterns in an Image:
Spectral Pattern ( pixel values in different bands - 110, 49, 70……..)
Spatial pattern (contextual information)
Temporal information (e.g. agriculture)
Classification can be done on single or multiple bands of image as well as adding other raster GIS layers, various methods
Training Pixels/Samples
- are typical representative pixels’ values from each class of interest to be supplied to the computer or classifier to be used for the classification.
Analyst identifies the groups of pixels with similar spectral pattern
Each of the patterns represents a category of land cover class
The statistical properties of the patterns are used for categorizing all pixels of the image set
Describe 4 resolution types
1.Spectral resolution:
Panchromatic-brightness
Multispectral-multiple wavelengths
Hyperspectral-loads of different wavelengths
2.Spatial resolution: pixel size->pixel output
smaller pixels mean more clear view
- Radiometric resolution:“how many different
intensity levels can be discriminated by the remote sensor within a specific band
Number of digital levels that a sensor can use to express variability of brightness within the data. It
determines the information content.
The more digital levels, the more detail can be expressed
Most remote sensing imagery recorded with
quantized levels in the 0 – 255 (8-bit) range - Temporal resolution:
Refers to the frequency of data acquisition over
an area.
• Important :
– infrequent observational opportunities (e.g., when
clouds often obscure the surface)
– short-lived phenomenon (floods, oil spills, etc.)
– rapid-response (fires, hurricanes)
– detecting changing properties of a feature to
distinguish it from otherwise similar feature
More bits means more ____
clarity
Swath
the Image extent:
.Refers to the “Swath” with of image acquisition by a
satellite image
-length and width of what the sattelite actually captures
Number of images to cover study area
Generally, higher spatial resolution = smaller
area coverage per frame = more scenes
Data sources for terrain mapping(2)
Direct Measurement -survey -GPS -Contours points from a topographic map Remote Sensing -Aerial photos - Satellite data - LiDAR
point cloud data
Data collected by lider system
Terrrain Mapping- Contouring
The most common method for terrain mapping
Lines on a map that represent areas of constant
elevation are (connect points of equal elevation)
Contour interval: the
vertical distance between
contour lines
Digital Elevation Model(DEM) represents a regular array of _______ points.
tALK ABOUT dem
elevation
.Use known points and place onto pixel
-interpolate unknown pixels based on known pixels
. DEM dark areas are the lowest elevation, light areas are the highest
Triangulated Irregular
Networks (TINs)
A TIN approximates the land Surface with a series of non-overlapping triangles. In contrast to DEMs, TINs are Based on an irregular distribution of elevation points.
TIN is a special Vector Data Format of
representing continuous surface
Define Slope and Aspect
Slope measures -the rate of change of elevation expressed as percent slope or degree slope Aspect is the directional measure of slope -starts with 0° at the north, moves clockwise, and ends with 360° also at the north
Hill-shading
Also known as shaded relief It’s a simulation of terrain showing the intersection between sunlight and surface features Four factors control the visual effect of hill shading: 1. The sun’s azimuth – direction of incoming light (0 to 3600) 2. The sun’s altitude – elevation of sun above horizon (0 to 900) 3. Surface slope – 0 to 900 4. Aspect – 0 to 3600 .Computer derives surface slope and aspect from DEM
viewshed
A viewshed refers to the portion of the land
surface that is visible from one or more viewpoints.
The process for deriving viewsheds is called
viewshed or visibility analysis
Requires two sets of data
-A point or line layer containing
one or more view points (vertices
and nodes in case of line)
-A DEM (elevation raster)
or TIN layer
The basis of the analysis is the line-of-sight operation
-line-of-sight connects the viewpoint and the target
- if any land surface or object on the land raises above the line then the target is invisible
- Otherwise the target is visible
Example of the types of questions can be answered
-Which areas can be seen from a fire lookout tower that is 15 meters high?
-How frequently can a proposed disposal site be seen from an existing highway, while driving through the highway?
-Where the next communications repeater tower in a series should be located?
3-D perspective of terrain mapping- 4 PARAMETERS
Showing the terrain as it would have if viewed at an angle from an elevated place or an airplane.
Four parameters:
1. Viewing azimuth – the direction from the observer to
the surface (0 to 3600)
2. Viewing angle – the angle measured from horizon to
the altitude of the observer (0 to 900)
3. Viewing distance –between the viewer and the object
4. Z-scale is the ratio between the vertical scale and
the horizontal scale
Interpolated points: define
Interpolated: points not directly measured
DEM is ____ data
raster
eLEVATION DATA IS _____ DATA
RATIO
TINs is _____ data
vector
Vector Data: Triangulated Irregular Network(TINs)
T OR F:
You can convert Rasta to TIN but not TIN to Rasta
False
You can Convert TIN to Rasta but NOT rasta to TIN
For Rasta you need __ pixels around one pixel to figure out slope
-for rasta you need 8 pixels around one pixel to figure out slope
Parameters to viewshed analysis(5)
Parameters for Viewshed Analysis: . Height of observer . Viewing azimuth . Viewing radius . Vertical viewing angle limits . Tree Height
In the coordinate system, which variable represents elevation?
In general, a narrower contour interval is used when mapping more mountaineous terrain?
Which of the following does LiDar use to measure terrain?
Slope is calculated as?
The Highest value for sun altitude is ___while the highest value for sun horizon is ____
Answer: Z
Answer: True
Answer: Lazar Beam
Answer: Rise/Run
Answer: 90, 360
T OR F
Geomatics is just cartography and map making
F
WAY MORE THEN THAT
Define Cartography
“- is the art, science and technology of
making maps, plans, charts and globes
representing Earth or any celestial body at
any scale.
It involves things like color selection (art &
science), the positioning (art & science) of
items on the map for making it visually
appealing, as well as conveying accurate
geographic information using technology (GIS).
Geo-data characteristics
Spatial: 1.Vector -point,line,polygon 2.Raster -pixel Attribute: 1.Qualitative -ordinal -nominal
- Quantitative(continuous and discontinuous)
- interval
- ratio
What would Metadata on a map be?
.Sources of information
and how processed
.Accuracy reporting
Grid:
Graticules:
a network of evenly spaced horizontal and vertical lines used to identify locations on a map
are lines showing parallels of latitude and meridians of longitude for the earth
Map Limits vs, Map Extent
. Map limits: portion of graphics page where
map features are drawn
• Map extent: area of the earth’s surface to be
displayed (in actual ground units)
Rule of thumb for number of feature classes:
Maximum of __ Individual Colors
Maximum of __ shades of the same color
Rule of thumb for number of feature classes:
Maximum of 12 Individual Colors
Maximum of 7 shades of the same color
Describe CMYK and RGB colour
CMYK Subtraction of light by the cyan, magenta, yellow and black Inks from a white surface
RGB
Addition of red, green
and blue lights on a
black surface
Hue is _______ while Saturation is __________
1.Qualitative . Different colors represent different things ( land use, soil type, building type, positive/negative) Colors do not imply magnitude.
2.Quantitative Different colors represent different ranges (elevation, percentage, “amount of”, “number of”) Colors do imply magnitude
define figure-ground
Figure-ground organization is the spontaneous
separation of the figure in the foreground from an
“amorphous” background.
Geovisualization
Geo-visualisation can be defined as an integrated
approach of digital cartographic and scientific
computer graphics tools, techniques and
methodology for visualizing geo-environmental
data for understanding, interpretation and
assessment of environmental phenomenon.
• However it is all based on the digital principles of
Geographical Information Systems.
Magnetic North Pole
• For navigation, most common method of finding
direction is relative to the magnetic North Pole
• The Earth magnetic field is largely a dipole field but
it has higher order variations as well.
Notice that the direction of
the dipole axis does not
align with the rotation axis
A compass needle tries to
align with the field lines
Canadian Magenetic Observatories
Canadian Magnetic Observatories
“Magnetic observatories are permanent measuring stations that
monitor the geomagnetic field to very high accuracy over time
scales ranging from seconds to decades and beyond”. - nrcan
Magnetic Declination
A compass lines up with the horizontal component of the magnetic field in a direction called magnetic north. True north, on the other hand is the direction from a given location to the north geographic pole. The angle between magnetic north and true north is called magnetic declination.
• Declination in 1999: 13° 41′ W -Annual change: Increase 2.4′ -Since the annual change is increasing, treat it as positive. -Therefore Declination in 2015 is: = 13° 41' W + (16 x 2.4′) = 13° 41' W + 38.4' = 14° 19.4' W
Isogenic Chart
An Isogonic Chart is a graph that depicts the isogonic lines on the earth. Isogonic lines are lines that depict the earth's magnetic declination and along these lines, the earth's magnetic declination remains constant.
compass
Since a compass wants to align with the field lines it will point either up or down (relative to gravity) when it is away from the magnetic equator.
.To compensate for the tendency to point up or down, good compasses have weights to make the needle
lay flat
.Normally, a compass designed for using in the Northern Magnetic hemisphere can not be used in the
Southern hemisphere unless the weighting mass can be moved to opposite side of the needle.
Traditionally Latitude and Longitude were calculated by
• Traditionally,
Latitude calculated from the position of stars,
noon position of sun
Longitude calculated using an accurate clock set
to Greenwich Mean Time
Define Declination and Right Ascension
Declination: Measured from equator and its astronomical coordinate equivalent to latitude Right Ascension: Angle measured eastward along the equator from the celestial ``prime meridian``
nAUTICAL aLMANAC
Contains all the necessary information for celestial
navigation
sOLAR zENITH aNGLE
sOLAR ELEVATION ANLGE
Solar Zenith Angle (SZA or Zd): angel between the sun and the point directly above your head at solar noon Zenith = 90° from the horizon Solar noon – sun at the highest point in the day • SZA (Zd) = Latitude (fa) – Declination
Solar Elevation Angle (SA of ε): angle
between the sun and YOUR horizon
(you are the vertex of the angle)
• SA (ε) = 90 ° - |SZA|
Latitude = SZA + Declination
= 90 - SA + Declination
if the solar zenith angle is negative, the sun is in the ______ sky.
(if this angle is negative, the sun is in the northern sky;
positive-sun is in the southern sky)
Qiyas
To obtain their latitude, ancient Arabs navigators measured directly the altitude of the Pole Star using a simplest method, and was known as the science of qiyas, use of a finger width.
When held at arm’s length, the width of four fingers was considered to measure 4 isba’.
In a 360 degree circle there were 224 isba’.
It was considered that a day’s sailing due north would raise the Pole Star 1 isba’ from the horizon.
For those traveling on land, the isba’ was further divided into 8 zam. Thus land distances were often measured in zams.
Kamal
A more accurate, but still
simple instrument was
known as a kamal.
This was a small parallelogram of horn or wood
measuring about one by two inches with a string inserted
in the center, which had nine knots at measured intervals.
The end of the string was held in the teeth. The lower
edge of the horn was placed on the horizon while the horn
was moved along the string until the upper edge touched
the required star.
Vasco da Gama’s pilot used a kamal from Malindi to India
Mariners Brass Quadrant
A quarter of a circle made of wood or brass--came into widespread use for navigation around 1450, though its use can be traced back at least to the 1200s. • The scale spans 90 degrees and is divided into whole degrees. • A plumb bob establishes a vertical line of reference.
Astrolabe
• invented in Persia/Greeks • It is a flat metal ring marked off in degrees, with a rotating bar in the center. • It was used to measure the altitude of stars, planets, and the sun. • From these measurements it was possible to establish latitude, time. • Astrolabes were used until the 1500s, when the cross-staff came into use.
cross staff
• The cross staff measured altitude, by looking at the sun and establishing latitude. • Navigators preferred using a cross staff because it was much easier to use on a rolling ship. • Although it was easier to use, it became very unpopular after many navigators became blind from staring at the sun too long.
Sextant
• The cross staff measured altitude, by looking at the sun and establishing latitude. • Navigators preferred using a cross staff because it was much easier to use on a rolling ship. • Although it was easier to use, it became very unpopular after many navigators became blind from staring at the sun too long.
______North= points towards north star
True/Geographic North=points towards north star
Original name for GPS
NAVISTAR(USA system-well known)
-ONLY ONE COVERING WHOLE WORLD
Components of GPS
1. sPACE sEGMENT .24 satellite vehicles .20,200 km elevation above Earth .uses WGS84 2.User Segment 3.Ground Attennas 4.Monitor Stations 5. Master Station
Space segment of NAVISTAR uses which datum?
WGS84
Master control station for GPS is in _____,_______
Master control station at Schreiver AFB, Colorado
.5 monitor stations around the world
How does GPS measure distance?
Distance measurement Radio signal traveling at speed of light Measure time from satellite to user Accurate timing is the key to measuring the distance Satellite uses four atomic clocks ($100,000 each) on board.
Trilateration
Trilateration: Three Satellites (2D
Positioning)
Three Dimensional (3D) Positioning -4 sattelites
Selective Availability (S/A)
• The Defense Department dithered the satellite time
message, reducing position accuracy to some GPS users.
• S/A was designed to prevent America’s enemies from
using GPS against US and their allies.
• In May 2000 the Pentagon reduced S/A to zero meters
error for civilian uses:
• Enhanced 911 service
• Car navigation
• Adoption of GPS time standard
• Recreation
• S/A could be reactivated at any time by the Pentagon.
biggest factor influencing system
performance in GPS is…
User error
Errors are cumulative and increased by Positional Dilution of
Precision (PDOP)
Positional Dilution of Position(PDOP)
PDOP indicates the accuracy of a 3D GPS position based on the number of satellites and the geometry of satellite positions. PDOP ranges from 0-99. The lower the number, the more accurate the data. Any position with a PDOP over 7 or 8 is probably not worth collecting. More advanced GPS receivers can filter out poor DOP values.
Any position with a PDOP over __ or __ is probably not worth collecting.
7 or 8
T OR F
More Sattelites means higher accuracy
F
PDOP can actually be higher(worse) with more
Differential GPS used to
• Some errors can be factored out using mathematics and modeling.
• Differential GPS can reduce errors
Real-time
Post process
Differential GPS: use measured location and fixed location in order to determine difference
______ has highest ammount of sattelites
compass
Lab Exam Practice Questiions
- What are two common types of coordinate system in GIS?
- If we have a shapefile called cities and it contains population info for major cities in Canada, how could we check the population of Saskatoon?
- If we have Landsat image of Saskatchewan province and a saskatoon boundary shapefile, we only wany Landsat image of saskatoon area, wat function should we use?
- For Georeferencing an image, ground control points re necessae, which can be obtained from…?
- Google earth is used to view the ground(whether physical landscapes or structures) from above by using the _______ streamed in from googles servers?
- In order to view a location in Google Earth using the perspective view, which allows you to see the various landforms(such as peaks, hills, and valleys) in a pseudo-3D representation which layer needs to be turned on?
- If changes are made in the Data view or layer properties they will aslo be reflected in the layout view?
- Which of the following is not a key in map design?
- Attribute tables KEEPS
- In Arcmap “select by location” function requires two sets of layers which are known as?
- T OR F One of the major limitations in google earth pro is that it only can show coordinated of a location in decimal degrees?
- T OR F ARCGIS online gives you the ability to share the URL link of your map through facebook and twitter or embed your map on the website?
- What are two common types of coordinate system in GIS? A. projected and geographic coordinate system
- If we have a shapefile called cities and it contains population info for major cities in Canada, how could we check the population of Saskatoon? Open attribute table and check population in saskatoon
- If we have Landsat image of Saskatchewan province and a saskatoon boundary shapefile, we only wany Landsat image of saskatoon area, wat function should we use? Clip Tool
- For Georeferencing an image, ground control points re necessae, which can be obtained from…? An existing georeferenced image, georeferenced vector GIS file, GPS based field survey for collecting coordinates of a few identifiable features on the image
- Google earth is used to view the ground(whether physical landscapes or structures) from above by using the _______ streamed in from googles servers? Satellite Imagery
- In order to view a location in Google Earth using the perspective view, which allows you to see the various landforms(such as peaks, hills, and valleys) in a pseudo-3D representation which layer needs to be turned on? Terrain
- If changes are made in the Data view or layer properties they will aslo be reflected in the layout view? True
- Which of the following is not a key in map design? Neatline
- Attribute tables KEEPS NON-SPATIAL DATA
- In Arcmap “select by location” function requires two sets of layers which are known as? Target Layer and Source Layer
- One of the major limitations in google earth pro is that it only can show coordinated of a location in decimal degrees? FALSE
- ARCGIS online gives you the ability to share the URL link of your map through facebook and twitter or embed your map on the website? TRUE
