Basic Geodata Processing Exercise 1

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Aim of the exercise

The objective of this exercise is to get a feeling for geodata and start working with it. Understand the attribute table, sort it, select manually and export the selection.

Links to Wiki articles

• QGIS Interface

• Geodata Import in QGIS

• Layer Concept

• Attribute Table in QGIS

• Projections

Data

Download all datasets here, save the folder on your computer and unzip the file. The zip folder includes:

• nigeria_populated_places.shp (Points) Shapefile

• nigeria_boundaries.geojson GeoJSON

The shapefile for populated places contains data on human settlements in Nigeria, including cities, villages and others. The GeoJSON file for the boundaries of Nigeria contains information on the administrative boundaries at levels 2 and 4 with level 2 representing the whole country and level 4 being the states.

Tasks

1. Load both files into QGIS.

2. Add the OpenStreetMap basemap via the browser panel –> XYZ Tiles.

3. To familiarise yourself with the data, open the attribute table. Determine the location of the data and the type of information it contains. Understand the different columns and the data they contain in your attribute table and try to get an overview of which columns will be relevant and important for your analysis.

4. In the nigeria_populated_places layer, open the attribute table, select the feature for Zuyel, and zoom to the selected point.

Hint

The place starts with a Z so it might help to sort the name column in descending order.

5. Export Zuyel as its own GeoPackage. Check the projection and choose an appropriate CRS. Name it zuyel.gpkg.

Note

As no calculations are involved, e.g. area, WGS84 (EPSG:4326) is a good choice.

How do I know which CRS to choose?

EPSG.io has a database that you can search to find the appropriate CRS to use for a country. More information on Projections can be found in the Wiki or in the corresponding section in Modul 2 on Projections.

6. Repeat the steps for the layer nigeria_boundaries.geojson and only export the district in which Zuyel is located. Name it accordingly. To find the district use the Identify Features tool and then manually select the correct district in the attribute table.

7. Remove all the initial layers and then open the attribute table for each of your new layers and check that each layer only contains one feature.

8. Save your project.

Result

Fig. 33 This is how your output could look like in the end