Download - Lec_4_Key Propertires of Spatial Data
Key Properties of Spatial Data
Prof. Dr. Sajid Rashid Ahmad
Atiqa Ijaz Khan _ Demonstrator
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Key Properties of Spatial data
Projection
3D earth into 2D map
Accuracy
How well does the database info match
the real world
Scale
Ratio of distance on a map to the equivalent distance on the ground
Resolution
The size of the smallest feature able
to be recognized
Thursday, April 13, 2023Institute of Geology, University of the Punjab
3Projection
• “A map projection is a mathematical model for conversion of locations from a three-dimensional (3D) earth surface to a two-dimensional (2D) map representation.”
• “A map projection uses mathematical formulas to relate spherical coordinates on the globe to a flat, planar coordinates.” (ESRI)
• “It defines a spatial relationship between location on the surface of Earth to their relative locations on a flat map.” (ESRI)
• “It is a set of rules for transforming features from the 3-dimensional Earth onto a 2-dimensional display.”
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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• In GIS software, the layers MUST have same coordinate system
in order to overlay and function properly.
Otherwise, the locations will set out the space or mis-matches.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
5Coordinate System
• “It is a reference system used to represent a geographic feature within a common geographic framework.”
• It enable datasets to used common location for integration.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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• Coordinate systems enable geographic datasets to use common locations for integration.
• “A coordinate system is a reference system used to represent the locations of geographic features, imagery, and observations, such as Global Positioning System (GPS) locations, within a common geographic framework.” (ESRI)
• Several hundreds of geographic and few thousands of projected coordinate systems are available for use.
• One can define their own custom coordinate system.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
7Coordinate Parameters
• Each coordinate system is defined by the following:• Its measurement framework, which is either geographic or planimetric. • Units of measurement:
• typically feet or meters for projected coordinate systems, or, • decimal degrees for latitude-longitude.
• The definition of the map projection for projected coordinate systems.• Other measurement system properties such as a spheroid of reference,
a datum, one or more standard parallels, a central meridian, and possible shifts in the x- and y-directions.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
8Types of Coordinate System
• The following are two common types of coordinate systems: • A global or spherical coordinate system such as latitude-longitude. These
are often referred to as geographic coordinate systems.• A projected coordinate system such as universal transverse Mercator
(UTM), Albers Equal Area, or Robinson, all of which (along with numerous other map projection models) provide various mechanisms to project maps of the earth's spherical surface onto a two-dimensional Cartesian coordinate plane.
• Projected coordinate systems are referred to as map projections.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Geographic
Projected
Coordinate System CS
GCS
PCS
Coordinate System
Geographic System
Planar System
Thursday, April 13, 2023Institute of Geology, University of the Punjab
10Geographic Coordinate System (GCS)
• Always measured in: • Degree-Minute-Second (DMS)• Decimal Degree (DD)
• Origin is at:• Where Prime Meridian meets the Equator.
• In GIS:
Longitude Latitude
Positive Values Eastern Northern
Negative Values Western Southern
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Geographic Grid: is a Location reference system for spatial features
on the earth’s surface.
Parallel:• Line of Latitude in N-S
direction.• Similar to Y-values.• Measured From the
Equator.• As from 0-180 degrees.
(0-90)• Taking Equator as
Reference.
Meridian:• Lines of Longitude in E-
W direction.• Similar to X-values.• Measured Along the
Equator.• As from 0-360 degrees.
(0-180)• Taking Greenwich,
England as Prime Meridian.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Thursday, April 13, 2023Institute of Geology, University of the Punjab
13Parallels of latitude
0° latitude
northlatitude
southlatitude
90°N
Equator
LATITUDE
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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LONGITUDE
West Longitude
Meridians of longitude 0° longitudePrime Meridian
Greenwich, England
Thursday, April 13, 2023Institute of Geology, University of the Punjab
15Projected Coordinate System (PCS)
• “PCS is defined on flat, two-dimensional surface.” (ESRI)
• It is a 2-dimensional planar surface. (ESRI)
• It is designed for flat surface such as printed map or on a screen.
• A PCS inherits the components of a geographic coordinate system and also has:
• Projection: The mathematical transformation used to convert from geographic coordinates to planar (projected) coordinates.
• Parameters: Parameters used in the transformation. These parameters are specific to the projection.
• Units: Linear measurement for coordinates on the plane.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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• The PCS uses two axes: • the x-axis, representing east-west, and • the y-axis, representing north-south.
• They intersect at the origin, (0,0).
• Locations are defined relative to the origin, using the notation (x,y), where x refers to the distance along the horizontal axis, and y refers to the distance along the vertical axis.
• Points below the x-axis or to the left of the y-axis have negative values.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Universal Transverse Mercator (UTM)
Thursday, April 13, 2023Institute of Geology, University of the Punjab
18Universal Transverse Mercator
(UTM)
• UTM has its root back in 18th century, but come to use by WW-2.
• UTM defines two-dimensional, horizontal positions.
• It is divided into 6-degrees longitudinal strips.• The 1st strips starts at ‘International Date Line’. (180° by GCS)
• The zones are numbered from ‘West-to-East’.• So, zone-2 starts at 174° W to 168° W.• And, zone-60 starts at 174° E to Date Line.
• From 80 degree South to 84 degree North.
• It is also divided into 8-degree zones from equator.
• Each zone has Central Meridian, this is the only line that extends from Poles and perpendicular to Equator.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
191. On the southwest coast of Norway, grid zone 32V (9° of longitude in width) is extended further west, and grid zone 31V (3° of longitude in width) is correspondingly shrunk to cover only open water.
2. The four grid zones 31X (9° of longitude in width), 33X (12° of longitude in width), 35X (12° of longitude in width), and 37X (9° of longitude in width) are extended tocover what would otherwise have been covered by the seven grid zones 31X to 37X. The three grid zones 32X, 34X and 36X are not used.
UTM - Exceptions
Thursday, April 13, 2023Institute of Geology, University of the Punjab
20Accuracy
• “The degree to which a measured value conforms to true or accepted values.” (ESRI)
• “Accuracy can be defined as the degree or closeness to which the information on a map matches the values in the real world.”
• Accuracy is the closeness of results of observations to the true values or values accepted as being true.
• “Accuracy is the degree to which information on a map matches true real-world values.”
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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• Accuracy is a measure of correctness.
• Accuracy could be quantified as ‘Tolerance’.
• Example: • The distance between two points might be given as 173 meters plus or
minus 2 meters. These bands are generally expressed in probabilistic terms.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
22Types of Accuracy
Absolute
Horizontal
Vertical
Relative
Precession
Or Positional Accuracy
Types of Accuracy
Thursday, April 13, 2023Institute of Geology, University of the Punjab
23Types of Accuracy
• The two classes of accuracy used are as follows;
• Absolute Accuracy:• Measure of the location of features on a map compared to their true
position on the earth.
• Relative Accuracy:• Measure of the accuracy of individual features on a map when compared
to other features.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Thursday, April 13, 2023Institute of Geology, University of the Punjab
25Types of Accuracy
Horizontal Accuracy• For map on publication.
• Not more than 10% of X,Y positions of well-defined points must be within given tolerance as measured on the publication scale.
Vertical Accuracy• For contour map publications.
• Not more than 10% of the elevations tested shall be in error by more than one-half the contour interval.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
26Vertical ScaleHorizontal Scale
Thursday, April 13, 2023Institute of Geology, University of the Punjab
27Web-site
https://www.e-education.psu.edu/geog469/node/253
Visit to play and understand…
Thursday, April 13, 2023Institute of Geology, University of the Punjab
28Scale
• “Scales compare a distance measured on the map to the actual distance on the surface of the earth.”
• Scale is the relationship that the depicted feature on map has to its actual size in the real word.
• Scale is the measurement of the amount of reduction a mapped feature has to its actual counterpart on the ground.
• It represent the relationship of the distance on the map/data to the actual distance on the ground.
• It’s a ratio of distance on the map to the distance on the actual distance on the earth’s surface.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
29SCALE...!
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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• High Details• Small area
• 1:24,00 or larger
Large Scale
• Average• 1:24,00 – 120,000
Medium Scale
• Less Details• Large area• 1:120,000 or smaller
Small Scale
Types of Scale
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Small Scale
Large Scale
Thursday, April 13, 2023Institute of Geology, University of the Punjab
32Large Scale vs. Small Scale
Large Scale• Objects are relatively larger in
size.
• With High details objects.
• Covering the Small area.
• High RF factor.• 1:24,000; 1:50,000 etc.• But, smaller denominator.
Small Scale• Objects are relatively smaller in
size.
• With Low details objects.
• Covering the Large area.
• Small RF factor.• 1:250,000; etc.• But, larger numerator.
Don’t Ever CONFUSE it again… !!!
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Ways to Depict Map Scale
Scale
Verbal Scale Written Scale Scale Text
Fractional Scale
Representative Factor R.F.
Graphical Scale Linear Scale Scale Bar
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Representative Scale Scale BarStatement of Scale
Ways to Depict Map Scale
Thursday, April 13, 2023Institute of Geology, University of the Punjab
35Resolution
• “Resolution refers to the ability to recognize and distinguish features.” (ESRI)
• “Ability to separate closely spaced objects on an image or photographs.”
• It could be: low, medium, high, or even very high.
• It’s our choice, One single object can be shown in:• 1 pixel, or• 4 pixels.
• It depends upon:• Sensor technology,• Need for sensor, or user,• Distance between satellite and Earth.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Resolutions
SPATIALSmallest identifiable
area as a discrete object in an image
SPECTRAL No. of frequencies recorded = sensors
TEMPORALTime interval
between measurements
Thursday, April 13, 2023Institute of Geology, University of the Punjab
37SPATIAL RESOLUTION
Thursday, April 13, 2023Institute of Geology, University of the Punjab
38Important Points
Image is the Pictorial Presentation of Raster. Pixels are called as Picture elements. Size of Pixel gives the Resolution of the image. Smaller the Pixel size Larger will the Resolution. Every Raster is not image but every image is a Raster.
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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* Vegetation in Yellowish green, * Vegetation in Red.* Water in Gray, * Water in Black.
SPECTRAL RESOLUTION
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Spectral Resolution
MSS Multi-spectral Bands: 3-14
Hyper-spectral Bands: 24-224
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Example: for satellite in orange’s shade colors
Time
July 1 July 12 July 23 August 3
11 days
16 days
July 2 July 18 August 3
TEMPORAL RESOLUTION
Thursday, April 13, 2023Institute of Geology, University of the Punjab
42SPATIAL RESOLUTIONS
NOAA-AVHRR (1100 m)
GOES (700 m)
MODIS (250, 500, 1000 m)
Landsat TM and ETM (30 – 60 m)
SPOT (10 – 20 m)
IKONOS (4, 1 m)
Quick-bird (0.6 m)
Thursday, April 13, 2023Institute of Geology, University of the Punjab
43Serial No. Satellites Altitud
e (km) Bands (µm) Multi-spectral (m) Panchromatic (m)
Thermal (m) Purpose
01. Landsat-7 705 0.5-0.9, 2.03-2.3 30 15 60 Scientific, RS
02. Sea WiFS 705 0.40-0.88 1 (LAC), 4 (GAC)* - - Bio-Oceanic
03. SPOT-5 822 0.5-0.73 10 2.5-5 - Scientific/commercial
04. IKONOS 681 0.45-0.9 04 01 - Urban & Rural Mapping etc.
05. Orb-view 480 0.45-0.9 2.4 0.6 - Commercial, Civil Eng., etc.
06. Quick bird 480 0.45 -0.9 2.4 0.6 Climate change, Commercial, etc.
07. Worldivew-2 770 0.45-0.80 1.84 0.5 - Commercial as Google maps, etc.
*LAC: Local Area Coverage*GAC: Global Area Coverage
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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30 m resolution and 60 m resolution (thermal), 705 km orbit, 7 bands including thermal infrared, Manhattan, KS. Image, 2000 (USGS-EROS)
LANDSAT (30 m)
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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IKONOS (04 m)MSS
SPOT (2.5 m)
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Quick Bird (0.6 m)IKONOS (01 m) (Panchromatic)
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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Imagery and their price ranges
Thursday, April 13, 2023Institute of Geology, University of the Punjab
48Imagery free of cost
1. http://glcf.umd.edu/
2. http://glovis.usgs.gov/
3. http://www.usgs.gov/pubprod/
4. http://earthexplorer.usgs.gov/
Thursday, April 13, 2023Institute of Geology, University of the Punjab
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