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

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impossible to reproduce the original colors. To get around this, scanners use a process called dithering to approximate colors that don’t occur in the current color palette. Figure 2.13: Raster image in zooming [28]. The biggest disadvantage when using raster images locates at editing and manipulating image colors. As vector images are object-oriented while raster images are pixel oriented, in order to change pixel colors, a specific color or range of colors must be isolated from the rest to be changed. This work is quite a challenge for even experienced users. File Size For each raster image file, a large amount of information, including the exact location and color of each pixel in the grid, needs to be kept track to reproduce the image. This results in large file sizes for raster images. Higher resolutions (dpi) and greater color depths (the number of bits per pixel) produce bigger file sizes. A typical 2" by 3" 150 dpi black and white raster image logo will be less than 70 KB in file size. The same file saved as a 300 dpi 24-bit (millions of colors) raster image logo might be 100 times larger (over 7 MB). When creating and scanning raster images, raster file size becomes a real issue, as big files tend to make computer processor and hard drive work overtime. Transferring big files (over 1 MB) over the Internet requires a high speed Internet connection on both ends for timely uploads and downloads. In despite of these disadvantages, raster images are more practically than vector images as they are viewable via monitors or other display medium and it is impossible in practice to obtain vector images from a photo. File Formats Common raster image formats include BMP (Windows Bitmap), PCX (Paintbrush), TIFF (Tag Interleave Format), JPEG (Joint Photographics Expert Group), GIF (Graphics Interchange Format) , PNG (Portable Network Graphic), PSD (Adobe PhotoShop) and CPT (Corel Photo PAINT). Perfect graphical tools will combine images from vector and raster sources and provide editing tools for both, since some parts of an image could come from a camera source and others could have been drawn using vector tools. 2.4 Geographic Information Organization 2.4.1 Map Layers GIS organizes geographic information in terms of layers. A layer is a representation of geographic data on a map. For example, vector layers are collections of simple geographic elements of same type such as a road network (represented by lines), parcel boundaries (polygons), soil types (polygons), well locations (points) and so on. Examples of raster layers include an elevation surface, satellite imagery, land use and etc. Within the data frame, each layer that represents a specific geographic data is displayed and overlaid by the other layers to form a significant geographic representation in real world [5]. 11
2.4.2 Data Theme Figure 2.14: Multiple layers geographic representation. Based on the data themes concept, geographic information in GIS could be partitioned into a series of logical information layers rather than a random collection of objects. Hence, users can organize information in various data themes that described the distribution of a phenomenon and how each one should be represented across a geographic extent. Many data themes are best represented by a single layer such as soil types or well locations. Other themes like a transportation framework, are represented by multiple layers, where each feature (such as streets, intersections, bridges, highway ramps, railroads and so on) is represented by a separate layer. Figure 2.15: Themes for a area [30]. Each GIS can contain multiple themes for a common geographic area. The collection of themes acts as a stack of layers. Each theme can be managed as an information set independent of other themes. Each one has its own representation and could be a collection of points, lines, polygons, surfaces, rasters and so on. Because layers are spatially referenced, maybe they overlap one another and can be displayed in a common map display. So GIS analysis operations like polygon intersection can combine information between layers to discover and work with the derived spatial relationships. The concept of layer-based data themes implies that: • All layers must be georeferenced to a place on the Earth so that they can be combined together. The georeferencing process is accomplished by defining the geographic coordinate system for each dataset. • Layers can be combined in many ways such as following the ordered layers in a map or by employing operators or commands. Geographic operators can work with the relationships both 12
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: 4-foot logo. The file size is the s
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 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
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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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PostGIS Raster : Extending PostgreSQL for The Support of ... - CoDE

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