ENV103 Chap.8 Building a First Map in QGIS
Building a First Map in QGIS
Lab 2 is the first map. Using Auckland's volcanic field, you set the project CRS to EPSG 2193, import a shapefile, CSV tables and a raster, join tables to points, export and clean the result as a GeoPackage, build a convex-hull boundary with a 5 km buffer, and finish with graduated symbols and a print layout carrying every required map element.
The chapter keeps the steps in the order they depend on each other, because most first-map problems come from running a tool before its input exists.
What this chapter covers
- 01
The QGIS window and Project CRS
- 02
Importing vector, CSV and raster data
- 03
Table joins on a shared ID field
- 04
Exporting and cleaning a GeoPackage
- 05
Minimum bounding geometry and convex hulls
- 06
Buffers and temporary layers
- 07
Graduated symbols and the print layout
Worked example · free
Put the Lab 2 workflow steps in a working order
- +2Order: import layers, join tables, export to a GeoPackage, clean fields, create the convex-hull boundary, buffer it by 5 km, symbolise, then lay out the map.
- +1Export must come before cleaning, because a join only links tables inside the project; edits need a real file that holds the joined fields.
- +1The buffer belongs on the convex hull, not the points, because the lab extends the field boundary outward by 5 km.
Key terms
- Project CRS
- The project CRS is the coordinate reference system QGIS uses to draw every layer in a project.
- Table join
- A table join links two datasets through a shared unique attribute such as an ID field.
- Convex hull
- A convex hull is the smallest convex polygon that encloses a set of points.
- Buffer
- A buffer is the area within a set distance of a point, line or polygon.
- Print layout
- The print layout is the QGIS workspace where a finished map is composed with its legend, scale bar and title.
- Graduated symbol
- A graduated symbol changes size or colour in classes according to an attribute value.
- Temporary layer
- A temporary layer is a processing output held only in the open project until it is made permanent or exported.
Building a First Map in QGIS FAQ
Why did my buffer disappear after I reopened the project?
Processing outputs start as temporary layers. Saving the project does not save them, so they vanish when the project closes. Right-click the layer and choose Make Permanent, or export it, straight after running the tool.
How do I join a CSV to a point layer?
Add the CSV through the Data Source Manager as delimited text with No Geometry, then open the point layer's Properties, choose Joins and add the table, matching the shared ID fields. In Lab 2 the join field is volcano_id and the target field is fid.
Which elements does the Lab 2 final map need?
A north arrow, a legend, a title, a scale bar and your name, with the volcanoes symbolised in five graduated classes by elevation. The rubric asks for the map to be neat and easy to follow, so remove any layer that does not support the message.
How do I measure the distance between two volcanoes in QGIS?
First find both points, for example with a query or filter on the name field, so you are sure which features you are measuring. Then use the measure tool from the attributes toolbar, with the project in EPSG 2193 so the distance reads in metres. Report an approximate value, as the proforma question asks.
Assessment move
The fastest way to secure this chapter is to rebuild the Lab 2 map from scratch with the instructions closed, then open them only to check what you missed. Set the Project CRS first and make it a reflex. Practise the three import routes, vector, delimited text with No Geometry and raster, until you can do each without searching the menus.
Join a table, open the attribute table to confirm the join, and then export to a GeoPackage in EPSG 2193; say aloud why export comes before cleaning. Run Minimum bounding geometry and Buffer from the Processing Toolbox, and make both outputs permanent immediately. When you symbolise, choose the classification deliberately and write down why, then build a print layout with every mandatory element and export it at 300 DPI.
Finally, rehearse the query skills the proforma used: measuring between two named points, filtering on an age field, sorting by elevation and saving only selected features as a new layer. The in-lab test drew on the first two labs, so these moves were examined under time pressure, and they reappear in every later map you make, including the two maps your poster must carry.