Overview
This lecture explains how to convert address-based location data in a CSV file into geographic coordinates (geocoding) using QGIS and its MMQGIS plugin.
From CSV to Shapefile with Addresses
- Previous lecture covered converting CSV files with longitude and latitude to shapefiles.
- Sometimes, CSVs have address information (address, city, state, country) instead of coordinates.
- To use address-based data in GIS, addresses must be converted into coordinates (geocoding).
Geocoding in QGIS Using MMQGIS Plugin
- Geocoding is the process of turning addresses into geographic coordinates.
- QGIS does not include a geocoding tool by default; it requires installing the MMQGIS plugin.
- MMQGIS uses Google and OpenStreetMap APIs for geocoding.
- To install the plugin: go to Plugins > Manage and Install Plugins, then search and install "MMQGIS".
- After installation, the geocoding tool appears in the QGIS main menu under MMQGIS.
Geocoding Process Steps
- Open the geocoding tool, browse to the CSV file with addresses.
- Specify which fields represent address, city, state, and country (QGIS can auto-detect them).
- Select the desired API/web service for geocoding.
- Set output location for the new shapefile.
- Assign a file to capture any rows that cannot be geocoded (not found output list).
- Run the process; a new spatial layer is added to the map.
Managing Layers in QGIS
- Both the original and geocoded layers can be displayed in QGIS.
- Layers can be turned on/off or reordered for efficient spatial data management.
Key Terms & Definitions
- Geocoding — The process of converting address information into geographic coordinates (latitude and longitude).
- Shapefile — A widely-used geospatial vector data format for GIS software.
- MMQGIS — A QGIS plugin providing geocoding and other spatial data processing tools.
Action Items / Next Steps
- Install the MMQGIS plugin in QGIS if not already done.
- Practice geocoding a CSV file containing addresses.
- Review how to manage and organize layers in QGIS.