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

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5.2 Exporting Rasters User can export existing rasters from PostGIS database as many small raster files named image1.tif, image2.tif et etc. Each file corresponds to one row of a raster table. gdal_translate "PG:host=’localhost’ dbname=’’ user=’’ password=’’ table=’table_name’ mode=’1’" c:/temp/image\#.tif Or user can produce only one big raster file composed by available rasters of a raster table: gdal_translate "PG:host=’localhost’ dbname=’’ user=’’ password=’’ table=’table_name’ mode=’2’" c:/temp/image.tif 5.3 Get Raster Statistics • Get summary statistics The ST_SummaryStats(raster, band, exclude_nodata_value) function returns summary statistics consisting of count, sum, mean, stddev (standard deviation), min and max for a given raster band of a raster. Band 1 is assumed if no band is specified. By default, exclude_nodata_value parameter is true. SELECT rid, ST_SummaryStats(rast) As stats FROM dummy_rast; • Get pixel histogram The ST_Histogram(raster, band, categories, width[ ]) function returns a set of (min, max, count, percent) records summarizing raster data distribution for a number of categories(the number of resulting records) of a given band. Number of categories are autocomputed if it is not specified. Band 1 is assumed if no band is specified. The width[] parameter is an array that indicates the width of each category. If the number of categories is greater than the number of widths, the widths are repeated. SELECT rid, band, ST_Histogram(rast) As stats FROM dummy_rast; • Computes quantiles The ST_Quantile(raster, quantiles[]) function computes quantiles for a raster in the context of the population. A pixel value could be examined to be at 25%, 50%, 75% percentile of the raster data that contains all possible pixel values. SELECT ST_Quantile(rast, 0.75) As value FROM dummy_rast WHERE rid=1; • Get number of pixels The ST_ValueCount(raster, values[]) function returns a set of records containing a pixel band value and the number of pixels in a given band that have a given set of values. If no band is specified, band number 1 is used by default. By default nodata value pixels are not counted and pixel band values are rounded to the nearest integer. SELECT ST_ValueCount(rast) As value FROM dummy_rast WHERE rid=1; 5.4 Display Rasters Normally any softwares, that use GDAL to read raster and enable a database connection, are able to display raster directly from PostGIS database. Examples of such software include: • QGIS plugin 65
• gvSIG plugin • MapServer through GDAL Other softwares that do not support direct raster displaying but instead they allow displaying a vectorization of the raster. This is the case of any softwares that are used to display vector PostGIS queries such as OpenJump or ArcGIS 10. – OpenJump SELECT ST_AsBinary((ST_DumpAsPolygons(rast)).geom), (ST_DumpAsPolygons(rast)).val FROM dummy_rast WHERE rid=1; – ArcGIS 10 Same as OpenJump but without ST_AsBinary(): SELECT (ST_DumpAsPolygons(rast)).geom, (ST_DumpAsPolygons(rast)).val FROM dummy_rast WHERE rid=1; 5.5 Edit and Compute Rasters • Set pixel value The ST_SetValue(raster, band, geometricpoint, newvalue) function returns a new raster resulting from setting the value of a given band in a given column x and row y pixel or at a pixel that intersects a particular geometric point. Band number starts at 1 and is assumed to be 1 if not specified. UPDATE dummy_rast SET rast = ST_SetValue(rast,1, ST_Point(3427927.75, 5793243.95),100) WHERE rid = 1 ; • Reclass rasters The ST_Reclass(raster, band, reclassexpression, pixeltype, nodatavalue) function creates a new raster by applying a valid PostgreSQL algebraic operation that defines a class expression on the input raster band. The band number specifies the band to be changed. If it is not specified, it is assumed to be 1. All other bands are unchanged. The new raster will have the same georeference, width and height as the original raster. Use case: convert a 16 BUI band to a 8 BUI and so on for simpler rendering. ALTER TABLE dummy_rast ADD COLUMN reclass_rast raster; UPDATE dummy_rast SET reclass_rast = ST_Reclass(rast,2,’0-87:1-10, 88-100:11-15, 101-254:0-0’, ’4BUI’,0) WHERE rid = 1; • Clip rasters The ST_Clip(raster, band, geometry) function returns a new raster that is clipped by an input geometry. If no band is specified all bands are returned. SELECT ST_Clip(rast, ST_Buffer(ST_Centroid(ST_Envelope(rast)), 20), false ) FROM aerials.boston WHERE rid = 4; • Apply algebra operation The ST_MapAlgebraExpr(raster, band, pixeltype, expression) function creates a new one band raster by applying a valid PostgreSQL algebraic operation on the input raster band. Band 1 is assumed if no band is specified. The new raster will have the same georeference, width and height as the original raster but will only have one band. If pixeltype is given, then the new raster will have a band of that pixeltype. If pixeltype is passed NULL, then the new raster band will have the same pixeltype as the input rast band. 66
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Faculté de Sciences Appliquées Se
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Abstract Nowadays, in many applicat
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3.2.4 Overlapping Raster and Vector
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D.5 Geology, Geophysics and Geochem
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4.9 Raster cell [16]. . . . . . . .
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Chapter 1 Introduction 1.1 Context
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Chapter 2 Geographic Information Sy
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2.2.3 Imagery Figure 2.3: Polygon f
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Figure 2.8: Surface expressed by co
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4-foot logo. The file size is the s
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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 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
Page 73: SELECT rast As origin, ST_Resample(
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
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