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

More documents

Recommendations

Info

Figure 4.1: PostGIS Raster implementation. no pyramid propeties when a mask can be created as an independent band and reduced resolution coverages can be stored as a separate layer. So a single raster has everything essential to do basic GIS raster operations. It is thus not necessarily related to other rasters in the same table to be georeferenced. This choice makes PostGIS Raster very simple and flexible. 4.3 Spatial Reference Identifier A spatial reference system (SRS) or coordinate reference system (CRS) is a coordinate-based local, regional or global system used to locate geographical entities. A spatial reference system defines a specific map projection, as well as transformations between different spatial reference systems. A spatial reference system identifier (SRID) is a unique value used to identify projection and local spatial coordinate system. These coordinate systems form the heart of all GIS applications. In other words, SRID values associated with spatial objects can be used to constrain spatial operations. For instance, spatial operations (such as intersection, transformation and etc.) can not be performed between spatial objects with different SRIDs. Or, the result of any spatial method derived from two spatial objects is valid only if they have the same SRID that is based on the same unit of measurement and projection. 4.4 Raster Data Raster data is a matrix of cells (or pixels) organized into rows and columns (or a grid) where each cell contains a value representing information. Unlike vector format, data stored in raster format can be used to represent various real world phenomena like [16]: • Land use or soils data which is classified as discrete data. • Temperature, elevation or spectral data that comes from satellite images and aerial photographswhich are classified as continuous data. • Pictures such as scanned maps or photographs of drawings and buildings. 4.4.1 Usage With a simple data structure, raster is exceptionally useful for a wide range of applications. In GIS, the uses of raster data falls under four main categories: • Base maps A common way to use raster is as a background for displaying other vector layers. Three main sources of raster based maps are orthophotos, satellite imagery and scanned maps. 29
Figure 4.2: Information representation using raster data [16]. An thophoto, thophotograph or thoimage is an aerial photograph geometrically corrected such that the scale is uniform: the photo has the same lack of distortion as a map. Unlike an uncorrected aerial photograph, an orthophotograph can be used to measure true distances because it is an accurate representation of the Earth’s surface, being adjusted for topographic relief 1 , lens distortion 2 and camera tilt 3 . When orthophotographs are displayed underneath other layers, they provide user with confidence that map layers are spatially aligned and represent real objects. Figure 4.3: Basemap raster for road data [16]. • Continuous maps Due to the matrix of cells structure, rasters are well suited for representing and storing data that changes continuously across a surface. Elevation values measured from the Earth’s surface are the most common application of surface maps. For example, raster in Figure 4.4 displays elevation, where green cells show lower elevation and red, pink and white cells show higher elevation. Other values, such as rainfall, temperature, concentration and population density, can also be used in spatial analysis as cells representing surfaces are regularly spaced. • Thematic maps Rasters representing thematic data can be derived from other data through analyzing operations. A common analysis application is classifying a satellite image by landcover categories. Basically, this activity groups the values of data into classes (such as vegetation type) and assigns a categorical value. Figure 4.5 is an example of a classified raster data that expresses the human use of land. Thematic maps can also result from geoprocessing operations that combine data from various sources such as vector, raster and terrain data. For example, user can process data through a geoprocessing model to create raster data that maps suitability for a specific activity. • User-defined attributes Digital photography and scanner are output devices that capture real world phenomena into digital world for long-term storage. Raster data is means by which digital 1 http://en.wikipedia.org/wiki/Topography. 2 http://en.wikipedia.org/wiki/Barrel_distortion. 3 http://en.wikipedia.org/wiki/Camera_tilt. 30
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 and 22: 2.4.2 Data Theme Figure 2.14: Multi
Page 23 and 24: measures of latitude. Longitude mea
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: Attribute information Table 4.1: Po
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
Page 73 and 74: SELECT rast As origin, ST_Resample(
Page 75 and 76: • gvSIG plugin • MapServer thro
Page 77 and 78: SELECT ST_AsJPEG(rast) As rastjpg F
Page 79 and 80: FROM buff_temp GROUP BY id ORDER BY
Page 81 and 82: Chapter 6 Application Most of GIS a
Page 83 and 84: 6.2 Tools Figure 6.3: PostGIS conne
Page 85 and 86: Figure 6.6: Band area. controlled b
Page 87 and 88: Figure 6.10: The loading map parall
Page 89 and 90:
Figure 6.14: Maps representing worl
Page 91 and 92:
Figure 6.17: Maps with a color lege
Page 93 and 94:
their levels of awareness of geogra
Page 95 and 96:
[15] Jorge Arevalo. PostGIS Raster
Page 97 and 98:
Appendix A PostGIS Raster Utilisati
Page 99 and 100:
eturn "Version 0.1" def qgisMinimum
Page 101 and 102:
Appendix C Code Implementation C.1
Page 103 and 104:
name="" # Setting table name and mo
Page 105 and 106:
Figure D.1: Synthetic aperture rada
Page 107 and 108:
D.4 Digital Image Processing D.4.1
Page 109 and 110:
Figure D.4: Age of the sea floor. M
Page 111 and 112:
Appendix F Continuous Surfaces One
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?