Top 100 QGIS Commands for Efficient Mapping and Spatial Analysis
QGIS (Quantum GIS) is one of the most powerful open-source tools available for Geographic Information System (GIS) professionals and spatial analysts. It offers a vast array of commands that enhance your mapping and spatial analysis experience. In this article, we’ll explore the top 100 QGIS commands that every GIS expert should know. Whether you’re a beginner or an advanced user, mastering these commands will significantly boost your productivity and accuracy.
Why Learn QGIS Commands?
Understanding and mastering QGIS commands offers numerous benefits, including:
- Enhanced Productivity: Speed up repetitive tasks with command shortcuts.
- Advanced Spatial Analysis: Leverage powerful analysis tools to derive meaningful insights.
- Customization: Create tailored workflows to suit your specific needs.
- Better Mapping: Improve your map-making with efficient and accurate command use.
Now, let’s dive into the top 100 QGIS commands that can transform your GIS experience.
1. Zoom to Layer (Ctrl+Shift+L)
A simple yet essential command that zooms to the extent of a selected layer, making it easier to focus on the area of interest.
2. Pan Map (Spacebar + Mouse Drag)
Quickly move across the map without altering the zoom level. This command is perfect for exploring large datasets efficiently.
3. Open Attribute Table (Ctrl+T)
The attribute table is a vital part of any GIS project. Use this command to quickly open and explore the data associated with your layers.
4. Select Features by Value (Ctrl+Shift+F)
This command allows users to select features based on attribute values, simplifying the process of working with subsets of data.
5. Field Calculator (Ctrl+I)
One of the most powerful QGIS tools for performing complex calculations on attributes. The Field Calculator allows you to add new fields or calculate field values based on formulas and expressions.
6. Buffer Tool
The Buffer tool creates buffer zones around selected features, a crucial operation for proximity analysis. Use this tool to assess areas of influence or create specific zones of interest around features.
7. Reproject Layer
Reprojecting layers is necessary when working with different coordinate reference systems (CRS). This command ensures that all layers align properly within the same spatial framework.
8. Clip (Vector > Geoprocessing Tools > Clip)
The Clip command allows you to extract portions of a vector layer based on the extent of another layer, perfect for focusing on smaller geographic regions.
9. Merge Vector Layers
Use this command to combine multiple vector layers into a single layer, streamlining the dataset for analysis or mapping.
10. Intersect (Vector > Geoprocessing Tools > Intersect)
The Intersect command helps find common areas between two layers. This tool is invaluable for spatial overlay analysis.
11. Merge Selected Features (Ctrl+M)
This command merges selected features within a layer into a single feature. It’s useful when you need to combine polygons or lines for simplified data management.
12. Simplify Geometry (Vector > Geometry Tools > Simplify Geometry)
This tool reduces the complexity of geometric shapes, optimizing them for faster processing while maintaining essential structure and topology.
13. Add Basemap (Web > QuickMapServices > Add Basemap)
Quickly add basemaps such as OpenStreetMap, Google Maps, or other map services directly to your QGIS project for a better context in your mapping projects.
14. Raster Calculator (Raster > Raster Calculator)
The Raster Calculator allows users to perform mathematical operations on raster layers, enabling complex analysis, such as combining or manipulating raster data.
15. Save As GeoPackage (Right-click > Save As > GeoPackage)
GeoPackage is a flexible, efficient, and open format for spatial data. Use this command to save vector and raster layers into a single, portable file format.
16. Clip Raster by Mask (Raster > Extraction > Clip Raster by Mask)
Clip your raster data based on a vector layer’s mask. This command is essential for focusing on specific areas in raster datasets.
17. Create Grid (Vector > Research Tools > Create Grid)
Generates a regular grid (square or hexagonal) over your map area. This tool is useful for creating reference grids for field data collection or spatial analysis.
18. Spatial Query (Select by Location)
Select features based on spatial relationships to other features in the map. For example, you can select all features that intersect with another layer.
19. Create Layer from Selected Features
This command allows you to extract a subset of features from a layer and create a new layer containing only the selected items. Ideal for focused analysis.
20. Generate Contours (Raster > Extraction > Contour)
Generate contour lines from raster data (e.g., elevation data). This command is essential for topographic map creation.
21. Field Calculator (Ctrl+I)
This tool allows users to create new fields in attribute tables and perform complex calculations or expressions on the existing fields.
22. Buffer Tool (Vector > Geoprocessing Tools > Buffer)
Create buffer zones around vector features, which are useful for proximity analysis, environmental planning, and proximity studies.
23. Rasterize (Vector to Raster)
Convert vector layers into raster format, preserving the spatial extent, and pixelizing vector data based on specified resolutions.
24. Join Attributes by Location
This tool joins attributes from one layer to another based on spatial location, allowing you to enrich your data with additional context.
25. Create New Shapefile Layer (Layer > Create Layer > New Shapefile Layer)
This command helps you create new shapefile layers to add new data types (points, lines, or polygons) to your project.
26. Extract by Attribute (Raster > Extraction > Extract by Attribute)
Extract raster values based on specific attribute queries. This can be especially useful for isolating data points or analyzing patterns within a specific attribute range.
27. Reclassify Raster (Raster > Conversion > Reclassify)
The Reclassify tool allows users to group raster values into ranges and assign new values to those groups, ideal for classification or thematic analysis.
28. Field Statistics (Vector > Field Calculator > Field Statistics)
Calculate basic statistics (e.g., sum, mean, min/max values) for a given attribute field. It’s useful for quickly analyzing the distribution of your data.
29. Export to KML (Right-click Layer > Export > Save Features As > KML)
Convert your vector data to KML format for use in Google Earth or other mapping platforms.
30. Rasterize a Polygon (Raster > Conversion > Rasterize (vector to raster))
Convert polygon data into a raster grid, assigning pixel values based on the polygon’s attributes.
31. Query Builder (Layer > Query Builder)
Build SQL-style queries to select specific features based on complex attribute and spatial conditions. This allows advanced filtering and analysis.
32. Create Spatial Index (Vector > Geometry Tools > Create Spatial Index)
Spatial indexing helps speed up the processing of vector layers. This tool is essential when working with large datasets.
33. Snap to Vertex (Digitizing Toolbar > Snapping Options)
Enable snapping to vertices when editing geometries, ensuring that your features align precisely with one another during digitizing.
34. Polygonize (Raster > Conversion > Polygonize)
Convert raster data into vector polygons. This tool is often used for vectorizing raster datasets such as classified images.
35. Raster to Point (Raster > Conversion > Raster to Point)
Convert raster values into points. This is useful when you want to extract sample data from a raster dataset for analysis or further processing.
36. Add Delimited Text Layer (Layer > Add Layer > Add Delimited Text Layer)
This command allows you to import data from CSV, Excel, or other text formats, and georeference it based on coordinate columns.
37. Print Layout (Project > New Print Layout)
Create high-quality print maps with customizable layouts. This feature is essential for producing professional cartographic outputs from QGIS.
38. Polygon Centroids (Vector > Geometry Tools > Extract Centroids)
Extract the centroid of polygon features as points, often used for creating a reference point or for calculating spatial properties.
39. Create Virtual Layer (Layer > Create Layer > New Virtual Layer)
Create virtual layers using SQL queries, enabling you to combine or transform layers without physically modifying the underlying data.
40. Identify Features (Ctrl+Shift+I)
The Identify tool is essential for exploring the details of specific features in your map, including attributes, geometry, and related information.
41. Add Plugin (Plugins > Manage and Install Plugins)
Install new plugins to extend QGIS functionality. The QGIS plugin library includes thousands of tools for various tasks such as advanced spatial analysis, map styling, and more.
42. Clip Vector (Vector > Geoprocessing Tools > Clip)
Clip vector data using another polygon layer as a boundary. This command is useful for extracting relevant data within specific regions.
43. Create Points from Polygons (Vector > Geometry Tools > Extract Points)
Extract the vertices or points from polygon geometries to create a new point layer, useful in spatial analysis or sampling.
44. Export Selected Features
This command allows users to export selected features from a layer to a new shapefile or other formats, useful when you need to isolate data for further processing.
45. Add WMS Layer (Layer > Add Layer > Add WMS/WMTS Layer)
Add web map services (WMS) to your QGIS project for interactive, live maps from online sources.
46. Calculate Geometry (Field Calculator > Calculate Geometry)
Quickly calculate geometric properties of features, such as area, length, and perimeter. This is a key tool for spatial analysis tasks.
47. Vector to Polyline (Raster > Conversion > Vector to Polyline)
Convert vector data into polylines, which can be used for network analysis or detailed geometric representations of data.
48. Delete Duplicate Geometries (Vector > Geometry Tools > Check Geometries)
This tool helps clean up your vector layers by removing any duplicate geometries, ensuring better data quality and accuracy.
49. Apply Style (Right-click Layer > Properties > Symbology)
Apply custom styling to your layers, enhancing the readability and visual appeal of your maps.
50. Count Points in Polygon
This command counts the number of point features within the boundary of each polygon in your vector layer. It’s useful for density analysis and other spatial queries.
51. Create Line from Points (Vector > Geometry Tools > Points to Path)
Create a line from a series of points, useful for trace routing or path analysis.
52. Field Mapping (Field Calculator > Expression Builder)
Map values from one field to another using expressions and conditions to automate data management tasks.
53. Delete Identical (Vector > Data Management Tools > Delete Identical)
Remove duplicate features from a layer based on specified attributes, ensuring the dataset is clean and without redundancy.
54. Snap to Grid
Ensure that digitized points or lines are aligned to a predefined grid. This is crucial for large-scale mapping or city planning projects.
55. Create Polygon from Multipoint
Convert a multipoint layer into a polygon, simplifying the analysis of scattered data.
56. Extract by Mask (Raster > Extraction > Extract by Mask)
Use a polygon layer as a mask to extract specific portions of a raster layer.
57. Vector to Raster (Vector > Conversion > Rasterize)
Convert vector features (such as polygons) into raster grids, essential for pixel-based analysis.
58. Georeference Raster (Raster > Georeferencer)
Align a raster image to real-world coordinates by assigning control points, which is crucial for integrating scanned maps or satellite imagery.
59. Delete Empty Fields
Remove attribute fields with no values in your vector data, which can help clean up datasets and make them more manageable.
60. Run Python Script
Execute Python scripts directly within QGIS to automate tasks or apply custom analysis techniques.
61. Save Map as Image (Project > Export > Export as Image)
Save your map layout as an image file for easy sharing or publication.
62. Assign Projection (Layer > Layer CRS > Assign CRS)
Assign a coordinate reference system (CRS) to a layer to ensure consistency with other datasets.
63. Merge Layers (Vector > Data Management > Merge Vector Layers)
Merge multiple vector layers into a single unified layer, simplifying data management.
64. Raster to Vector (Raster > Conversion > Polygonize)
Convert raster data into vector polygons for detailed analysis.
65. Draw Polygon (Digitizing Toolbar > Draw Polygon)
Digitize new polygons directly on your map canvas.
66. Reorder Layers
Reorder layers in the Layer Panel to adjust the display order, ensuring proper map stacking and visibility.
67. Save Project (Ctrl+S)
Save your QGIS project to avoid losing your work and maintain a record of changes.
68. Zoom to Full Extent (Ctrl+Shift+E)
Quickly zoom to the full extent of all layers in the project to get an overview of the entire map.
69. Show/Hide Layer (Layer Panel)
Toggle the visibility of layers in the Layer Panel to focus on specific data during analysis.
70. Export Map to PDF
Create a high-quality PDF map that can be easily shared or printed.
71. Advanced Digitizing Toolbar
This toolbar provides advanced options for digitizing vector features, including tools for exact angle, length, and area specifications, making your data entry more precise.
72. Select by Polygon (Select Features > Select by Polygon)
Use this tool to select features by drawing a polygon around them, allowing you to choose multiple features within the defined boundary.
73. Field Statistics
Calculate statistics like mean, median, sum, and others for a particular field in your attribute table. This helps in quick data analysis.
74. Invert Selection (Ctrl+Shift+I)
This command inverts the current selection in your layer, so all unselected features become selected and vice versa.
75. Advanced Field Calculator (Field > Field Calculator > Advanced)
Use this version of the Field Calculator to apply more complex expressions and perform intricate calculations on attribute fields.
76. Create Hillshade (Raster > Analysis > Hillshade)
Generate a hillshade layer from raster elevation data. This is essential for visualizing terrain and enhancing 3D map views.
77. Undo (Ctrl+Z)
This common command undoes the last action, which is useful during data editing or map creation to quickly revert any unintended changes.
78. Redo (Ctrl+Y)
Reverses an undo action, allowing you to recover actions you’ve undone mistakenly.
79. Rasterize (Vector > Rasterize)
Convert vector features into raster format, useful for generating grid-based data analysis or visualizations.
80. Vector Simplification (Vector > Geometry Tools > Simplify)
This tool simplifies vector geometries, which can help reduce file sizes and improve performance, especially when dealing with large datasets.
81. Coordinate Capture Tool
This tool allows you to capture and display the geographic coordinates of any point on your map by clicking on it. This is especially useful for field data collection or reference.
82. Create a Fishnet Grid (Vector > Research Tools > Create Fishnet)
Generate a rectangular grid over your area of interest. This tool is often used for sampling, spatial analysis, or creating reference grids.
83. Clip Raster (Raster > Extraction > Clip Raster)
Clip raster layers by a defined boundary to focus on a specific region of interest, useful for analyzing smaller portions of a larger dataset.
84. Rotate Feature(s) (Digitizing > Rotate Feature(s))
Rotate selected features by a specific angle. This command is useful when editing geometries and adjusting map layouts.
85. Merge Lines (Vector > Geometry Tools > Merge Lines)
Combine multiple line features into a single line feature. This is helpful when working with line datasets and performing network analysis.
86. OpenStreetMap (OSM) Plugin (Plugins > Manage and Install Plugins)
This plugin allows you to load OpenStreetMap data directly into QGIS. It’s useful for working with global street and infrastructure data.
87. Simplify Lines (Vector > Geometry Tools > Simplify)
Reduce the complexity of line features by removing unnecessary vertices, making it easier to handle large datasets and speeding up performance.
88. Select by Value (Vector > Select by Expression)
Select features from a vector layer based on the attribute value. This tool enables you to filter data based on specific conditions.
89. Add PostGIS Layer (Layer > Add Layer > Add PostGIS Layer)
Connect to a PostGIS-enabled database to directly load and manage spatial data stored in PostgreSQL/PostGIS.
90. Create Polyline from Points (Vector > Geometry Tools > Points to Path)
Generate a polyline from a set of points. This is commonly used for routes, trails, or other linear features derived from point data.
91. Rasterize Multiple Layers (Raster > Conversion > Rasterize Multiple Layers)
Rasterize multiple vector layers at once, ideal for batch processing when you need to convert several vector datasets into raster format simultaneously.
92. Spatially Enabled DataFrame (Right-click > New Spatially Enabled DataFrame)
Create a new spatially enabled dataframe to interact with spatial data more efficiently within QGIS, especially when working with different layers in Python.
93. Grid and Contour Export (Raster > Extraction > Grid and Contour Export)
Export raster grids and contours into different formats, allowing users to share data or perform further analysis.
94. Label Features (Layer > Properties > Labels)
Enable and customize feature labeling for vector layers, ensuring that your maps are both informative and visually clear.
95. Show/Hide Panel (View > Panels > Show/Hide Panel)
Toggle the visibility of panels like the Attribute Table, Layers, and Map Composition to optimize your workspace and focus on specific tasks.
96. Create Polygon from Points (Vector > Geometry Tools > Create Polygon)
Generate a polygon layer from a set of points, useful for creating bounded regions from a series of point locations.
97. Field Calculator Expressions (Field > Field Calculator > Expressions)
Use advanced expressions in the field calculator for more control and customization when calculating or modifying field values.
98. Reproject Raster (Raster > Projections > Warp (Reproject))
Reproject raster data from one coordinate reference system (CRS) to another. This is a vital command for working with data from different geographic projections.
99. Raster to Polygon (Raster > Conversion > Raster to Polygon)
Convert raster data into vector polygons, which can then be analyzed in a vector format for finer control or thematic mapping.
100. Customize Toolbar (View > Toolbars > Customize)
Customize your QGIS toolbar to quickly access the most frequently used commands. This tool can greatly improve workflow efficiency, especially for advanced users.
Conclusion
Mastering these top 100 QGIS commands will significantly enhance your spatial analysis, mapping, and data processing capabilities. Whether you’re performing basic tasks like zooming to a layer or complex analyses like raster reclassification, these commands will improve your productivity and efficiency in QGIS. By learning and implementing these commands, you can streamline your workflows, create professional maps, and perform advanced spatial operations that will elevate your GIS projects.
