PostGIS Raster : Extending PostgreSQL for The Support of ... - CoDE

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within and between layers. • GIS layers can be combined from many sources and many users. In fact, most users are dependent on one another for portions of the data they want to use. So interoperability becomes a fundamental feature in GIS. 2.5 Georeference and Coordinate Systems 2.5.1 Georeference All elements in a map have a specific geographic location and extent that enable them to be located on the Earth’s surface. So to georeference something means to describe its existence on the Earth’s surface. The term is used when establishing the relation between raster or vector images and coordinates or when determining the spatial location of other geographical features. Examples would include establishing the correct position of an aerial photograph within a map or finding the geographical coordinates of street address. The georeferencing procedure is thus imperative for modeling geographical data in the field of geographic information systems. 2.5.2 What Is a Coordinate System? Figure 2.16: Georeferencing a geographic object [26]. A coordinate system is a system that uses coordinates to uniquely determine the location of a point or other geographic element on the Earth. There are two common types of coordinate system used in GIS: • A global or spherical coordinate system such as latitude-longitude. This system is often referred to as geographic coordinate system. • A projected coordinate system based on map projection. There exist different map projections that provides various mechanisms to project maps of the Earth’s spherical surface onto a twodimensional Cartesian coordinate plane. Projected coordinate systems are also referred to as map projections. Geographic Coordinate Systems A geographic coordinate system is a coordinate system that enables every location on the Earth to be specified by a set of numbers. The coordinates are often chosen such that one number represents vertical position and two or three numbers represent horizontal position. A common choice of coordinates is latitude and longitude. Latitude and Longitude are the angles from the center of the Earth to a measured point on the Earth’s surface. Latitude measures are angles in a north-south direction. The equator is at an angle of 0. Often, the northern hemisphere has positive measures of latitude and the southern hemisphere has negative 13
measures of latitude. Longitude measures are angles in an east-west direction. Longitude measures are traditionally based on the Prime Meridian, which is an imaginary line running from the North Pole through Greenwich, England to the South Pole. This line has longitude as 0. West of the Prime Meridian is often recorded as negative longitude and east is recorded as positive. Figure 2.17: The location of the measured point (in red) is latitude plus 40 degrees and longitude plus 50 degrees [26]. Although longitude and latitude can locate exactly any positions on the surface of the globe, they are not uniform in units. Only along the equator, the distance represented by one degree of longitude approximate the distance represented by one degree of latitude. This is because the equator is the only parallel line of latitude that is as large as a meridian line of longitude. Figure 2.18: Parallels lines of latitude and meridians line of longitude [26]. Above and below the equator, the circles defining the parallel lines of latitude get gradually smaller until they become a single point at the North and South Poles. As the meridians converge toward the poles, the distance represented by one degree of longitude decreases to zero. For example, one degree of longitude at the equator equals 111.321 km, while at 60 ◦ latitude, it is only 55.802 km. Since degrees of latitude and longitude don’t have a standard length, distances or areas can not be measured accurately or display the data easily on a flat map. Efficient GIS analysis and mapping applications require a more stable coordinate framework, which is provided by projected coordinate systems. Projected Coordinate Systems using Cartesian coordinates Projected coordinate systems are any coordinate system designed for a flat surface. 2D and 3D Cartesian coordinate systems provide the mechanism for describing the geographic location of geographic objects using x, y and z values. The x,y measurements represent the position on the Earth’s surface and the z represents the height above or below sea level. 2D Cartesian coordinate system is a coordinate system that uses two axes: one horizontal x representing east-west and one vertical y representing north-south. The point at which these axes intersect is the origin. Locations of objects are defined relatively to the origin using the notation 14
Page 1 and 2: Faculté de Sciences Appliquées Se
Page 3 and 4: Abstract Nowadays, in many applicat
Page 5 and 6: 3.2.4 Overlapping Raster and Vector
Page 7 and 8: D.5 Geology, Geophysics and Geochem
Page 9 and 10: 4.9 Raster cell [16]. . . . . . . .
Page 11 and 12: Chapter 1 Introduction 1.1 Context
Page 13 and 14: Chapter 2 Geographic Information Sy
Page 15 and 16: 2.2.3 Imagery Figure 2.3: Polygon f
Page 17 and 18: Figure 2.8: Surface expressed by co
Page 19 and 20: 4-foot logo. The file size is the s
Page 21: 2.4.2 Data Theme Figure 2.14: Multi
Page 25 and 26: 2.6 GIS Applications 2.6.1 Crime Ma
Page 27 and 28: 2.6.3 Traditional Knowledge GIS Tra
Page 29 and 30: These additional functionalities ma
Page 31 and 32: Figure 3.3: Physical storage of Geo
Page 33 and 34: DROP INDEX spain_images_idx; CREATE
Page 35 and 36: In summary, the intersection is muc
Page 37 and 38: Attribute information Table 4.1: Po
Page 39 and 40: Figure 4.2: Information representat
Page 41 and 42: for discrete data while floating-po
Page 43 and 44: the matrix are parallel to the x-ax
Page 45 and 46: Lines Figure 4.15: Raster point rep
Page 47 and 48: Choosing an appropriate cell size i
Page 49 and 50: The multi-band conception is result
Page 51 and 52: "32BUI" = 32-bit unsigned integer "
Page 53 and 54: Figure 4.30: Pyramids at different
Page 55 and 56: ectangular because there might be s
Page 57 and 58: Figure 4.39: Vector to raster conve
Page 59 and 60: Figure 4.42: Web application with o
Page 61 and 62: In this example, the dummy_rast tab
Page 63 and 64: One approach to make this intersect
Page 65 and 66: 4.19 Intersection The fact that Pos
Page 67 and 68: Figure 4.51: Raster and raster inte
Page 69 and 70: ST_Present and ST_Passes predicates
Page 71 and 72: Chapter 5 User Guide Sometimes stor
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SELECT rast As origin, ST_Resample(
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• gvSIG plugin • MapServer thro
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SELECT ST_AsJPEG(rast) As rastjpg F
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FROM buff_temp GROUP BY id ORDER BY
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Chapter 6 Application Most of GIS a
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6.2 Tools Figure 6.3: PostGIS conne
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Figure 6.6: Band area. controlled b
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Figure 6.10: The loading map parall
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Figure 6.14: Maps representing worl
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Figure 6.17: Maps with a color lege
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their levels of awareness of geogra
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[15] Jorge Arevalo. PostGIS Raster
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Appendix A PostGIS Raster Utilisati
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eturn "Version 0.1" def qgisMinimum
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Appendix C Code Implementation C.1
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name="" # Setting table name and mo
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Figure D.1: Synthetic aperture rada
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D.4 Digital Image Processing D.4.1
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Figure D.4: Age of the sea floor. M
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Appendix F Continuous Surfaces One
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