------Using GIS-Fundamentals of GIS
Review:
NR 143 Final Exam
Final Exam: Monday, May 7
10:30-1:15
110 Aiken
Closed book/notes
Fundamentals of GIS
Topics and format
question topic
number
points
percent
Remote Sensing
10
46
23.0%
Raster Analysis
7
34
19.0%
Public Data
5
23
11.5%
Spatial Reference
3
21
10.5%
Geocoding
3
19
9.5%
Metadata
2
14
7.0%
Data Quality (error)
3
13
6.5%
GPS
3
13
6.5%
TIN
2
9
4.5%
Data Structures
2
8
4.0%
40
200
100.0%
17
80
40.0%
medium answer
5
40
20.0%
multiple choice
20
80
40.0%
41
200
100.0%
question type
short answer
Review of some important, post-midterm material follows.
Don’t forget to study spatial reference and data structures!
Fundamentals of GIS
Topic detail
Remote Sensing
Terms, sensor properties & types of resolution, comparison of sensors,
classification techniques, electromagnetic spectrum, spectral response
curves….
Raster Analysis
Techniques and their purposes, surface tools, filters, viewshed….
Public Data
Acronyms, important datasets and what is included with each, compare….
Spatial Reference
Projection types, terms & concepts, compare, scale factor, PCS’s….
Geocoding
Components and purpose, different approaches and their result….
Lecture Materials by Austin Troy except where noted © 2008
Fundamentals of GIS
Topic detail continued
Metadata
Why metadata? Sections and components? Terms….
Data Quality (error)
Terms, error types, quantitative vs. qualitative data….
GPS
Satellite system terms, differential GPS, sources of error….
TIN
Purpose(s), creating a TIN, parameters, advantages….
Data Structures
Field types, storage unit characteristics….
Lecture Materials by Austin Troy except where noted © 2008
------Using GIS-Fundamentals of GIS
Raster Analysis
Fundamentals of GIS
Raster data
Raster Elements
–Extent
–# rows
–# columns
–Coordinates
–Origin
–Orientation
–Resolution
–Grid cell
------Using GIS-Fundamentals of GIS
Reclassification with Grids
Here we reclass to
3 classes, based
on natural breaks
------Using GIS-Fundamentals of GIS
Raster Analysis Overview
Raster calculator
• Raster overlay queries
– Example: [elevation > 2500] AND [slope > 20]
• Raster overlay calculations
– Example: [soil_depth_1990] – [soil_depth_2000]
• Zonal Statistics
• Raster terrain functions (hillshade, slope, aspect, contours)
• Viewshed Analysis
Terrain + Points = Visibility raster
• Neighborhood Statistics & Filters
• Distance Functions & Density
Local * Focal * zonal * global
Fundamentals of GIS
Viewshed analysis
Inputs/outputs? Parameters?
In this case, red is for tower 1, blue for 2 and green for 3
Lecture Materials by Austin Troy except where noted © 2008
------Using GIS-Fundamentals of GIS
Raster terrain functions in ArcGIS
Hillshade:
Illumination /
brightness values
Slope:
Rise / run
expressed as
percent slope OR
as angle (degrees)
Contours:
User-defined
interval and
base contour
Lecture Materials by Austin Troy except where noted © 2008
Aspect:
Azimuth angle of
steepest path
(orientation or
bearing of the
slope direction)
------Using GIS-Fundamentals of GIS
Zonal Statistics
• Summarize the mean,
max or sum for some
value within each of the
bounding units
• Polygon and Raster
• Raster and Raster
• Here we summarize by
subdivision zones the
mean soil erodibility
value (from our
calculation).
Lecture Materials by Austin Troy, Brian Voigt and Weiqi Zhou except where noted © 2011
Fundamentals of GIS
Neighborhood Statistics (Focal)
• A method of summarizing raster data within a neighborhood by a
statistical measure, like mean, std dev.
– Neighborhood shape
– Neighborhood settings
• Window size
• Units
– Statistic types
Fundamentals of GIS
Neighborhood Filters
Filter types
– Low pass filters – remove noise (emphasize trends)
– High pass filters – edge enhancement (emphasize
local detail)
------Using GIS-Fundamentals of GIS
Distance Analysis
Used to answer questions related to distance
– Proximity
– Straight Line Distance Measurement
– Cost Weighted Distance Measurement
– Shortest Path
Fundamentals of GIS
Density Functions
• Use sample points to
create density surfaces
• Can use a z value, or
it can simply be based
on the abundance and
distribution of points.
• Output: number of
points per unit area of a
designated
neighborhood
------Using GIS-Fundamentals of GIS
Terrain Analysis
------Using GIS-Fundamentals of GIS
Slope, Aspect, Contours
55
• Raster slope is calculated by
steepest path in neighborhood
54
• Aspect is direction of steepest path
53
(azimuth in degrees)
• Critical for flow path analysis,
watershed generation, drainage
network and viewshed analysis, etc.
• Contour generation
51
48
43
36
45
38
------Using GIS-Fundamentals of GIS
Three Dimensional data — TIN
• Triangulated Irregular Network
• Irregular distribution of
elevation sample points
• Breaklines
• Z-tolerance (~resolution)
• Delauney triangulation
------Using GIS-Fundamentals of GIS
ArcScene
• 3D visualization
• Extrude a third dimension
• Drape thematic layers on elevation
• Create animations (fly-through)
------Using GIS-Fundamentals of GIS
3D Visualization
------Using GIS-Fundamentals of GIS
Public Data
Fundamentals of GIS
• Acronyms!
GIS Data
TIGER
NED
NAIP
SRTM
DEM DOQ DRG
Imperviousness
DLG
NWI
Hypsography CLU
GNIS
SSURGO NHD
NLCD
hydrography
• What’s included? How do they compare?
1/3 arc second
Scale?
7.5 minute
• USGS National Map
30m resolution
Fundamentals of GIS
The difference between an aerial photograph
and an orthophoto
• Aerial photo
• Orthophoto
– image displacement caused
by tilting of camera and
terrain relief
– scale is not uniform
– cannot measure distances
on a photograph
Light travels
longer distance at
scene edge:
magnification
– rectified to remove nonconstant scale due to
varying distance to camera
– Also adjusts for elevation
and tilt
– Therefore possible to
measure distances directly
like on other maps
– Can serve as a base map
onto which other info may
be overlaid
------Using GIS-Fundamentals of GIS
Geocoding & Digitizing
Fundamentals of GIS
What is Geocoding?
• Convert lists/spreadsheets to features (needs a
mechanism to calculate coordinates for the address)
• Address matching: uses street address database,
created from a streets layer
Address table + reference layer = point features
• Reference layer defined in ArcCatalog as “address
locator”
• Takes advantage of ref. layer attributes & topology
(left/right)
• Geocoding accuracy = fn(reference layer accuracy)
Fundamentals of GIS
Geocoding example: 1060 Main Street
It looks for Main street, then for the 1000-1100 block
L-F-ADDR
1000
1001
Main St
direction
R-F-ADDR
• Point is placed on even (upper) side of
street
• Position of 1060 is interpolated
L-T-ADDR
1100
1101
R-T-ADDR
1060 Main St
Fundamentals of GIS
Geocoding in ArcGIS
ArcCatalog:
Specify reference file
Specify address range
attributes
Specify zone
Specify rules for
address list
Tools >> Geocode addresses
Fundamentals of GIS
Geocoding and Error
100 m
100 m
300 m
Fundamentals of GIS
Geocoding and Error
Rural street segments are also more subject to greater error
because longer street segments means more interpolation
A rural area with a long road
segment: very imprecise
An urban road segment: smaller,
more precise
Fundamentals of GIS
XY Geocoding
We can also create points from a table by their latitude and longitude
Do this by clicking:
• Then we specify the lat and
long fields as well as the
spatial reference system
• Lat and Long should be in
decimal degrees
CA hazardous waste sites
Fundamentals of GIS
Digitizing
• Tablet digitizing
• Heads-up digitizing
Often “drawing” features over an orthophoto base
------Using GIS-Fundamentals of GIS
GPS
Fundamentals of GIS
GPS
• GPS (NAVSTAR): one of two GNSS – Global
Navigation Satellite System…. GLONASS is the other….
more coming
• 30 NAVSTAR satellites; need at least 3 to determine
location (better to have 4 or more)
r2
r1
r3
Fundamentals of GIS
How Does GPS Work?
• We need at least 3 satellites as reference points (better
to have 4 or more)
• Position is calculated using trilateration
Fundamentals of GIS
How Does GPS Work?
• Calculating range (distance from satellite to receiver)
Distance = Velocity * Time
• Time determined from lag in pseudo-random code, one from
satellite and one generated at the same time by the receiver.
• 4th satellite helps with time synch
Sent by satellite at time t0
Received from
satellite at time t1
Source: Trimble Navigation Ltd.
Fundamentals of GIS
Sources of Error
•
•
•
•
Gravitational effects
Atmospheric effects
Obstruction & Multipath
Satellite geometry….
PDOP
• Selective Availability
Fundamentals of GIS
Locating Satellites
• Need to know satellite locations to determine
geometry/PDOP
• Ephemeris and Almanac are part of transmitted
signal
Fundamentals of GIS
How does DGPS work?
• One stationary & one moving receiver …. error
• The stationary receiver must be located on a known
control point …. Correction factor sent to rover
------Using GIS-Fundamentals of GIS
Remote Sensing
Fundamentals of GIS
Electromagnetic Radiation
Radiation
Source
• Electromagnetic Spectrum
Wavelength
(Micrometers)
.01
UltraViolet
.04
.07
Visible
Visible
1.0
Near IR
3.0
Shortwave IR
Panchromatic
Film
Color
Film
IR Film
Spectral Imagery
5.0
Midwave IR
14.00 um
Longwave IR
Visible comprises 2%
of EM Spectrum
Fundamentals of GIS
Passive Detection
Camera or sensor
scattering
absorption
transmittance
Fundamentals of GIS
Reflectance
Reflectance
High
Low
0.4mm
Blue
0.5mm
Green
0.6mm
Red
0.7mm
Fundamentals of GIS
So, what are RS data?
• RS imagery is raster data.
• Each picture element (pixel) has a
value, or digital number (DN).
Fundamentals of GIS
Spectral Response Curves
50
R
E
F
L
E
C
T
A
N
C
E
Grass
40
Concrete
30
Sandy loamy
Soil
Fallow field
20
Asphalt
Artificial turf
Clear water
10
(%)
0
BLUE
0.4
GREEN
GREEN
0.5
Visible
RED
0.6
0.7
Wavelength (micrometers)
0.8
Near IR
1.3
Fundamentals of GIS
Band Placement
Silty-clay soil
Turbid river water
75
1 2
3
4
1 2
3
4
Vegetation
Muck soil
Clear river water
5
7
Landsat TM
LANDSAT 7 PAN
MSI
PAN
IKONOS & HI RES
50
visible
B G R
Near IR
Wavelength, mm
Mid IR
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0
0.6
25
0.4
Percent Reflectance
100
Fundamentals of GIS
Multispectral Display
Band Composite Output =
Color Guns =
Band Combination =
Landsat TM Band
4
7
2
BLUE
GREEN
RED
NEAR IR
SHORT
WAVE IR
1
2
3
4
5
(LANDSAT)
MIDWAVE IR
7
LONGWAVE IR
6
Fundamentals of GIS
Landsat band combination comparisons
3-2-1
True (natural)
color composite
4-3-2
Color infrared
composite (CIR)
4-5-2
False color
composite
Fundamentals of GIS
Sensor Properties
• Spatial resolution
(pixel size)
Landsat 30m
IKONOS 4m
• Spectral resolution
(# bands)
Visible
Multispectral
Band
1
.45-.52
Band
2
.53-.62
Orthophoto 0.5m
Near IR
Band
4
.79-.90
Band
3
.63-.69
Band
5
1.55-1.75
Hyperspectral
100s of Bands
Ultraspectral
1000s of Bands
• Radiometric resolution
– bit depth
• Temporal resolution
– orbital period
(return rate)
©
S
SWIR p
a
c
Band
e
I 7
m
2.08-2.35
a
g
i
n
g
LWIR
Band
6
10.4-12.4
Fundamentals of GIS
Trade-offs
Aerial Photo
IKONOS
Landsat
© Space Imaging
Spatial Resolution
# Bands
Radiometric Resolution
Temporal Resolution
½m
4m
30m
1
4
7
8 bit
11 bit
8 bit
On demand
3-4 days
16 days
Compare also: SPOT, Quickbird, ASTER
Fundamentals of GIS
Active Sensors
transmitted signal
received signal
•
IfSAR – Inferometric Synthetic
Aperture Radar
•
LIDAR – LIght Detection And
Ranging
Fundamentals of GIS
Major Satellite Systems
• High spatial resolution
– Quickbird, IKONOS, OrbView-3, SPOT-5 PAN, IRSP6
• Medium spatial resolution
– Landsat-5 TM, Landsat-7 ETM+, ASTER, SPOT
• Low spatial resolution
– MODIS, ENVISAT, GOES, AVHRR, MSS
Fundamentals of GIS
Orbits
• Most of these satellites are in sun-synchronous orbit
• Satellite passes over the same part of the Earth at
roughly the same local time each day
• ~8 degrees inclined from polar orbit, allowing
match with earth’s rotation
• Maintains sun angle
Source:
http://hdsn.eoc.nasda.go.jp/experience/r
m_kiso/satellit_type_orbit_e.html
Fundamentals of GIS
Scanners
• Pushbroom (along track) vs.
Whiskbroom (across track)
• LANDSAT (MSS, TM, ETM+)
• SPOT (HRV)
• IKONOS
• Compare resolution(s), other
characteristics
• Off-nadir viewing
Source: http://www.sci-ctr.edu.sg/ssc/publication/remotesense/spot.htm
Materials by Austin Troy and Weiqi Zhou except where noted © 2008
Fundamentals of GIS
Image Pre-Processing
• Create a more faithful representation through:
– Geometric correction
– Radiometric correction
– Atmospheric correction
• Image enhancement
–
Spatial feature manipulation: Spatial filtering, edge enhancement, and Fourier
analysis…. Low-pass & high-pass filters
–
Contrast manipulation: Gray-level thresholding, level slicing, and contrast
stretching.
–
Multi-image manipulation: Band ratioing, principal components, vegetation
components, canonical components…. Orthophoto vs. “true” orthophoto
• Rectification – remove distortion (platform, sensor, earth, atmosphere)
…. Scanned aerial photo vs. orthophoto
Fundamentals of GIS
Image classification
• Turn RS data into meaningful information (feature extraction)
• Spectral pattern recognition – supervised vs. unsupervised
…. training sites
• Spatial pattern recognition
• Temporal pattern recognition
• Applications – land cover mapping (Anderson classification)
• Accuracy assessment
Fundamentals of GIS
Object-oriented classification: 3 Steps
• Segmentation
• Feature
extraction
• Classification
Fundamentals of GIS
Object-oriented Classification
B
C
------Using GIS-Fundamentals of GIS
Data Quality & Documentation
(Error & Metadata)
Fundamentals of GIS
Data Quality
• Accuracy + Precision = Quality
• Error = fn(accuracy, precision)
• Cost vs. quality tradeoff
• Random vs. Systematic error Which can be controlled?
• Positional accuracy
SCALE
• Attribute accuracy & precision (quantitative vs.
categorical)
Standards
Fundamentals of GIS
Other measures of data quality
• Logical consistency
• Completeness
• Data currency/timeliness
• Accessibility
Common sources of error?
Fundamentals of GIS
Error ….
• Accuracy & Precision
•Positional vs. Attribute Accuracy
•Propagation (single step)
• Cascading (multi-step)
• Cascading error can be managed
to a certain extent by conducting
“sensitivity analysis”
Conflation
• Attribute
• Feature
(2 types)
Image source: http://oopslist.com/
Fundamentals of GIS
Documentation and Metadata
• Purpose?
• Federal mandate…. FGDC (“Content Standard for
Digital Geospatial Metadata”)
• Terminology!
Fundamentals of GIS
Documentation and Metadata
Some roles/purposes of metadata:
1. Information retrieval, cataloguing, querying and
searching for data electronically.
2. Describing fitness for use (applicability) and
documenting the usability and quality of data.
3. Describing how to transfer, access or process data
4. Documenting all relevant characteristics of data needed
to use it
5. Data permanence; creates institutional memory;
advertises an organization’s research (generate
partnerships)
Fundamentals of GIS
Documentation and Metadata
• Metadata
usually
include
sections
similar to
these
Materials by Austin Troy © 2008
Fundamentals of GIS
Documentation and Metadata
Critical components usually break down into:
1. Dataset identification, overview
2. Data quality
3. Spatial reference information
4. Data definition
5. Administrative information (distribution)
6. Meta-metadata