Lec_4_Key Propertires of Spatial Data
Download as PPTX, PDF2 likes572 views
This document discusses key properties of spatial data including projection, accuracy, scale, and resolution. It defines projection as the conversion of 3D earth coordinates to a 2D map representation using mathematical formulas. Accuracy refers to how closely a map matches real-world values, which can be measured horizontally, vertically, or relatively. Scale compares distances on a map to actual distances on earth. Resolution is the smallest feature that can be recognized on a map.
Lec_4_Key Propertires of Spatial Data
- 1. Key Properties of Spatial Data Prof. Dr. Sajid Rashid Ahmad sajidpu@yahoo.com Atiqa Ijaz Khan _ Demonstrator atiqa_ss09@yahoo.com
- 2. 3D earth into 2D map How well does the database info match the real world Ratio of distance on a map to the equivalent distance on the ground The size of the smallest feature able to be recognized Institute of Geology, University of the Punjab Tuesday, November 11, 2014 2 Key Properties of Spatial data Projection Accuracy Scale Resolution
- 3. Projection • “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.” Institute of Geology, University of the Punjab Tuesday, November 11, 2014 3
- 4. • 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 4
- 5. Coordinate 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 5
- 6. • 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 6
- 7. Coordinate 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 7
- 8. Types 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 8
- 9. Geographic Projected Coordinate System GCS Institute of Geology, University of the Punjab Tuesday, November 11, 2014 9 CS PCS Coordinate System Geographic System Planar System
- 10. Geographic Coordinate System (GCS) • Always measured in: • Degree-Minute-Second (DMS) • Decimal Degree (DD) • Origin is at: • Where Prime Meridian meets the Equator. • In GIS: Institute of Geology, University of the Punjab Tuesday, November 11, 2014 10 Longitude Latitude Positive Values Eastern Northern Negative Values Western Southern
- 11. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 11 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.
- 12. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 12
- 13. 90°N Institute of Geology, University of the Punjab Tuesday, November 11, 2014 13 Parallels of latitude 0° latitude north latitude south latitude Equator LATITUDE
- 14. Greenwich, England Meridians of longitude 0° longitude Institute of Geology, University of the Punjab Tuesday, November 11, 2014 14 LONGITUDE West Longitude Prime Meridian
- 15. Projected 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 15
- 16. • 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 16
- 17. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 17 Universal Transverse Mercator (UTM)
- 18. Universal 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 18
- 19. UTM - Exceptions 19 1. 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 to cover 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014
- 20. Accuracy • “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.” Institute of Geology, University of the Punjab Tuesday, November 11, 2014 20
- 21. • 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 21
- 22. Types of Accuracy Institute of Geology, University of the Punjab Tuesday, November 11, 2014 22 Types of Accuracy Absolute Horizontal Vertical Relative Precession Or Positional Accuracy
- 23. Types 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 23
- 24. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 24
- 25. Types 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 25
- 26. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 26 Horizontal Scale Vertical Scale
- 27. Web-site Institute of Geology, University of the Punjab Tuesday, November 11, 2014 27
- 28. Scale • “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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 28
- 29. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 29
- 30. Types of Scale Large Scale Medium Scale Small Scale Institute of Geology, University of the Punjab Tuesday, November 11, 2014 30 • High Details • Small area • 1:24,00 or larger • Average • 1:24,00 – 120,000 • Less Details • Large area • 1:120,000 or smaller
- 31. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 31 Small Scale Large Scale
- 32. Large 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 32 Don’t Ever CONFUSE it again… !!!
- 33. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 33 Ways to Depict Map Scale Scale Verbal Scale Written Scale Scale Text Fractional Scale Representative Factor R.F. Graphical Scale Linear Scale Scale Bar
- 34. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 34 Statement of Scale Representative Scale Scale Bar Ways to Depict Map Scale
- 35. Resolution • “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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 35
- 36. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 36 Resolutions SPATIAL Smallest identifiable area as a discrete object in an image SPECTRAL No. of frequencies recorded = sensors TEMPORAL Time interval between measurements
- 37. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 37 SPATIAL RESOLUTION
- 38. Important 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. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 38
- 39. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 39 * Vegetation in Yellowish green, * Vegetation in Red. * Water in Gray, * Water in Black. SPECTRAL RESOLUTION
- 40. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 40 Spectral Resolution MSS Multi-spectral Bands: 3-14 Hyper-spectral Bands: 24-224
- 41. July 2 July 18 August 3 11 days 16 days Institute of Geology, University of the Punjab Tuesday, November 11, 2014 41 Example: for satellite in orange’s shade colors Time July 1 July 12 July 23 August 3 TEMPORAL RESOLUTION
- 42. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 42 SPATIAL 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)
- 43. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 43 Serial No. Satellites Altitude (km) Bands (μm) Multi-spectral (m) Panchromatic (m) Thermal (m) Purpose *LAC: Local Area Coverage *GAC: Global Area Coverage
- 44. LANDSAT (30 m) Institute of Geology, University of the Punjab Tuesday, November 11, 2014 44 30 m resolution and 60 m resolution (thermal), 705 km orbit, 7 bands including thermal infrared, Manhattan, KS. Image, 2000 (USGS-EROS)
- 45. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 45 IKONOS (04 m) MSS SPOT (2.5 m)
- 46. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 46 Quick Bird (0.6 m) IKONOS (01 m) (Panchromatic)
- 47. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 47 Imagery and their price ranges
- 48. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 48 Imagery free of cost
- 49. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 49