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

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Chapter 4 PostGIS Raster This section deals with representing raster structure and explaining from how raster is stored to the mechanisms used to index, retrieve raster in PostgreSQL. It is also important to address the way that raster and vector layers overlap - a relevant feature that makes PostGIS Raster more robust than ORACLE GEORaster. 4.1 Implementation PostGIS Raster chooses to implement a minimal raster data structure. That means that a raster type is as simple as a single type and is stored in a single table. This data structure is very similar to the one of PostGIS vector data and very different from the Oracle Spatial SDO_GEORASTER and SDO_RASTER raster structures. In PostGIS Raster: • One table with a column of type raster is referred to as a raster coverage. • One table row with a column of type raster corresponds to one tile. The choice of such simple data structure will facilitate the achievement of four objectives described in Chapter 3. With a single raster type, it implies that each raster attribute is a complete and self sufficient georeferenced raster. So raster attributes composing a table are not necessarily related to each other to form a significant coverage. This also means that: • Rasters from the same table may have different size. • The upper left corner and the pixel size of a raster are not necessarily the same values as those of another rasters. They may therefore snap to different grids. • Finally, different rasters may overlap like polygons in a vector layer may overlap. This is a fundamental feature to implement meaningful vector to raster conversions in which all attributes of a vector are conserved in the resulting raster table. In this case, if the vector features and the data values part of the resulting raster features do not necessarily overlap, the nodata values of the raster features will overlap. In addition, PostGIS Raster provides also a raster_columns table to help application get a quick overview of raster tables and information (such as metadata) related to the rasters stored in these tables. 4.2 Structure PostGIS Raster implements only one type of raster instead of two like SDO_GEORASTER and SDO_RASTER in Oracle Spatial. It supports no metadata when a raster contains all data about itself such as attribute information, georeference information, band information and band data. Figure ?? describes these components in details [6]. As shown in this figure, a raster has no mask and 27
Attribute information Table 4.1: PostGIS Raster structure. Description Storage version Raster format version unsigned 16 bit integer band number Number of raster bands stored in the raster unsigned 16 bit integer width Width of the raster unsigned 16 bit integer heigh Height of the raster unsigned 16 bit integer Georeference information Description Storage pixelsizex Pixel size in the x-direction in the same map units as the coordinate system pixelsizey Pixel size in the y-direction in the same map units as the coordinate system upperleftx X-coordinate of the center of the upper left pixel upperlefty Y-coordinate of the center of the upper left pixel 64 bit double 64 bit double 64 bit double 64 bit double rotationx Rotation about x-axis 64 bit double rotationy Rotation about y-axis 64 bit double srid Y-coordinate of the center of the upper left pixel 32 bit integer Band information (one set per band) Description Storage isoffline Flag specifying if raster data is stored in the database or as a file in the file system 1 bit hasnodatavalue Flag specifying if nodatavalue exists or not 1 bit pixeltype Pixel type of the band 4 bits nodatavalue Nodata value of the band Depend on band pixel type Band data (one set per band) for in-db raster Description Storage values[] An array of pixel values Depends on band pixel type and size Band data (one set per band) for out-db raster Description Storage bandnumber Number of the out-db band unsigned 8 bit integer path Path to the out-db raster file string 28
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: In summary, the intersection is muc
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
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
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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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PostGIS Raster : Extending PostgreSQL for The Support of ... - CoDE

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