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QGIS Workflows & Spatial Data Management

Welcome to Day 3 of the Hydrological Modelling Training Plan. Today, we transition from spatial concepts and raw satellite data to hands-on desktop GIS operational workflows. Using QGIS Desktop, you will master spatial data management, cartographic styling, tabular calculations, geoprocessing algorithms, spatial queries, and database integrations.

Learning Objectives

By the end of today's sessions, you will be able to:

  • Navigate the QGIS user interface, configure directories, manage file paths (Relative vs. Absolute), and troubleshoot project backup files (.qgz~).

  • Evaluate and deploy hydrology-specific QGIS plugins (including WhiteboxTools, GRASS, SAGA, QSWAT, RiverGIS, FLO-2D, and FREEWAT) classified by operational priorities to solve specialized catchment, hydraulic, and groundwater modeling problems.

  • Apply professional cartographic symbology (single symbol, categorized, graduated, rule-based) and label rendering for vectors, as well as configure raster color ramps, hillshades, contours, and transparency blending.

  • Perform table schema adjustments, typecasting, field calculations (physical vs. virtual fields), tabular joins, and write advanced relational aggregate query expressions.

  • Run core vector geoprocessing tools (buffering, clipping, dissolving, intersections, difference) and validate/repair topological geometry errors.

  • Process raster datasets using map algebra (Raster Calculator), reproject/resample grid grids, reclassify continuous grids, and execute raster-vector conversions (polygonize/rasterize).

  • Query spatial datasets using OGC spatial predicates, spatial joins, zonal statistics (on administrative boundaries and custom digitized polygons), and proximity/hub distance matrices.

  • Integrate OGC web services (WMS, WMTS, WFS, WCS) and modern RESTful OGC APIs (Features, Tiles, Coverages, EDR) into your QGIS workspace.

  • Deploy a local PostGIS database using Docker Compose, import vector datasets, and write spatial SQL queries to run server-side geoprocessing.

Course Syllabus & Roadmap

The day is structured into 13 comprehensive topics:

flowchart TD
    subgraph Row1 [" "]
        direction LR
        M1["1. Intro to QGIS Desktop<br/>(Interface & Projections)"] --> M2["2. Plugins & Extensions<br/>(PyQGIS & Core Plugins)"] --> M3["3. Hydrology Plugins<br/>(Whitebox, GRASS, SAGA, QSWAT)"] --> M4["4. Workspace & Data <br> Management<br/>(Relative Paths & <br> GeoPackages)"]
    end
    subgraph Row2 [" "]
        direction RL
        M5["5. Symbology & Styling<br/>(Vector Styles & Raster Renders)"] --> M6["6. Attribute Data Operations<br/>(Calculations & <br> Virtual Fields)"] --> M7["7. Vector Geoprocessing<br/>(Spatial Overlays & <br> Validations)"] --> M8["8. Raster Processing<br/>(Map Algebra & <br> Resampling)"] --> M9["9. Georeferencing<br/>(GCPs & Transformations)"]
    end
    subgraph Row3 [" "]
        direction LR
        M10["10. Spatial Queries & <br> Neighborhoods<br/>(Predicates & <br> Zonal Stats)"] --> M11["11. Web GIS & <br> OGC Services<br/>(WMS/WFS & <br> Modern OGC APIs)"] --> M12["12. Spatial Databases<br/>(PostGIS Docker & <br> SQL Queries)"] --> M13["13. Practical Lab & Assignment<br/>(GIS Database Compilation)"]
    end
    M4 --> M5
    M9 --> M10

    %% Premium styled flowchart nodes
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    style M2 fill:#e3f2fd,stroke:#1565c0,stroke-width:2px
    style M3 fill:#e8f5e9,stroke:#2e7d32,stroke-width:2px
    style M4 fill:#e8f5e9,stroke:#2e7d32,stroke-width:2px
    style M5 fill:#f3e5f5,stroke:#6a1b9a,stroke-width:2px
    style M6 fill:#fff3e0,stroke:#d84315,stroke-width:2px
    style M7 fill:#fff3e0,stroke:#d84315,stroke-width:2px
    style M8 fill:#efebe9,stroke:#4e342e,stroke-width:2px
    style M9 fill:#fdf8e2,stroke:#f5b041,stroke-width:2px
    style M10 fill:#fce4ec,stroke:#c2185b,stroke-width:2px
    style M11 fill:#e0f2f1,stroke:#00695c,stroke-width:2px
    style M12 fill:#e0f7fa,stroke:#00838f,stroke-width:2px
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    style Row1 fill:none,stroke:none,stroke-width:0px
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    style Row3 fill:none,stroke:none,stroke-width:0px

Day 3 Course Materials:

  1. 01: Introduction to QGIS Desktop: Interface navigation, panels, projection settings, and coordinate display panels.

  2. 02: QGIS Plugins and Extensions: Installing core plugins, geoprocessing toolboxes, and an introduction to the PyQGIS Python console.

  3. 03: Hydrological Plugins and Integrated Tools: Prioritized directory of hydrology plugins covering WhiteboxTools, GRASS, SAGA, QSWAT, RiverGIS, FLO-2D, and FREEWAT.

  4. 04: Geospatial Data Management and Organization: Project relative path settings, project backup file recovery, folder architectures, metadata cataloging, Shapefiles vs. GeoPackages, Browser Panel operations, DB Manager client, and workspace consolidation (Package Layers).

  5. 05: Layer Symbology, Styling, and Labeling: Cartographic styling (Categorized, Graduated, Rule-Based), raster styling (Singleband gray, Pseudocolor, Hillshade, Contours), typography, and labeling outline text buffers.

  6. 06: Attribute Data and Table Operations: Schema structures, data types, geometry calculators, conditional logic CASE queries, virtual vs. physical fields, advanced aggregates, and tabular joins.

  7. 07: Vector Geoprocessing Operations: Buffering, clipping, dissolving, intersections, difference overlays, and fixing geometry self-intersections or bowtie errors.

  8. 08: Raster Processing and Map Algebra: Cell dimensions, Raster Calculator masking, warping, Bilinear resampling, reclassify by table, and polygonize/rasterize conversions.

  9. 09: Georeferencing in QGIS: Scanned paper maps, ground control points (GCPs), linear/polynomial/TPS transformations, resampling methods, and residual RMSE error analysis.

  10. 10: Spatial Queries and Neighborhood Analysis: Spatial predicates, select by location, spatial joins (one-to-one, summarized), zonal statistics overlay (on administrative bounds and custom digitized polygons), and hub distance matrices.

  11. 11: Web GIS and OGC Services: Remote servers, WMS/WMTS/WFS/WCS streaming protocols, modern RESTful OGC APIs (Features, Tiles, Coverages, EDR), public server connection exercises, and web publishing.

  12. 12: Spatial Databases and PostGIS: Relational databases, geometry vs. geography types, GIST indexing, spinning up PostGIS using Docker Compose, database connections, layer imports, and spatial SQL queries.

  13. 13: Practical Lab & Assignment: Multi-step geoprocessing workflows and 10 detailed practice exercises ranging from basic layer properties to advanced multi-criteria hub matrices, concluding with a comprehensive GIS database and watershed mapping layout assignment.