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

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Figure 6.8: The color legend interface. QGIS retrieves the temporal raster table from PostgreSQL using a connection string and a SQL command. The connection string is used to establish a connection to PostgreSQL. Its structure is ’PG: dbname=%s host=%s user=%s password=%s port=%s’. PostgreSQL then executes the SQL command and outputs temporal raster table list as a result. 6.3.1 Time Travel Loading Data To show the revolution in time of a set of temporal rasters, first of all, data need to be loaded from PostgreSQL into QGIS. There exist two approaches for loading temporal raster (or map). The first one attempts to load each map, one after another from PostgreSQL database into QGIS. When loading a map, there is a change from QGIS cursor to PostgreSQL cursor. That is because when QGIS establishes a connection to PostgreSQL, PostgreSQL will execute a request to retrieve a temporal raster row. When the map is loaded, necessary PyQt instructions like updating current time, progress slider bar etc. are need to be executed to show the evolution. In turn, a cursor change from PostgreSQL to QGIS occurs again before these instructions take place, as PyQt instructions are managed by QGIS cursor. These steps are exactly what will happen to the next loaded map and so on until the final loaded map. This approach sounds cumbersome and involves a lot of execution time due to cursor changes. Figure 6.9: The loading map sequential approach. In the second approach, all maps are loaded into QGIS memory once and for all. Hence, only two cursor changes are needed (one from QGIS to PostgreSQL and another from PostgreSQL to QGIS). Then, the visibility of each map is simply handled by turning on or off the check box corresponding to this map from the layers panel as described in the previous section. This approach reduces enormously execution time. Another advantage results from this is that all maps can be organized in an order (descending or ascending) by modifying the SQL command. The ordering can not happen in the first approach as each map is individually loaded. Pseudo code of function iniLayers that loads all layers into QGIS using the second approach: def iniLayers(self): Retrieve a list of temporal raster IDs to rids Change QGIS cursor to PostgreSQL cursor 77
Figure 6.10: The loading map parallel approach. For each rid in rids: Retrieve a layer from PostgreSQL using a connection string Try to add layer to qgis Come back to QGIS cursor Figure 6.11: Maps representing world climate [7] are loaded once time. Their visibility is handled by turning on/off the check boxes list. Media Control Each loaded map is identified by an ID. All map IDs are saved in a list layerIds. Only maps that have a time instant included in interval from Begin time to End time will be shown in the evolution. When the play media button is triggered, the first map that satisfies the time condition will be displayed. Subsequently, value in the Current time field is updated by time instant of the first map and the slider in the Time region moves by a step. Each step is at least equals the tick interval (by definition of tick interval in the previous section). Then a QTimer ctimer is necessary to increase the time interval between two displayed maps instances. Otherwise, all maps that satisfy the time range condition will be displayed nearly at the same time and human eyes can not recognize the succession of the maps. Users can drag and drop the speed slider to change this time interval from 0.05s to 2s. After the ctimer is time out, it triggers the displaying function displayLayer to display the second map and so on until the final map is reach. Pseudo code of function playMedia: If a map satisfies the time condition Display the map Update current time field Move slider Trigger ctimer Pseudo code of function displayLayer: Retrieve a map from a map id Turn on the visibility of this map 78
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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
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measures of latitude. Longitude mea
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2.6 GIS Applications 2.6.1 Crime Ma
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2.6.3 Traditional Knowledge GIS Tra
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These additional functionalities ma
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Figure 3.3: Physical storage of Geo
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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 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
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Page 89 and 90: Figure 6.14: Maps representing worl
Page 91 and 92: Figure 6.17: Maps with a color lege
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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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