Building and Analysing Sections

Data Preparation
Georeferencing
Creating Cross-Sections in QGIS Using Raster, Vector, and Point Cloud Data
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Duration: 30-40 minutes

NoteLearning Goals

By the end of this tutorial, you will be able to:

  • Drawing section lines
  • create multi-layer elevation profiles in QGIS using the built-in Elevation Profile tool.
  • Load raster, LAZ point cloud, vector data to analyse in section.
  • Digitize vector features (points, lines, polygons) from georeferenced maps
  • Create and edit vector layers with proper attributes
  • Compare data sets (vector vs raster vs LiDAR)
NoteSoftware and Data Required
  • QGIS (version 3.x or higher)
  • Freehand Raster Georeferencer plugin
  • Active internet connection (for PDOK aerial photos)
  • Data files:
    • NASA raster DEM
    • TU Delft LAZ point Cloud
    • Vector LineString

Steps

Part 1 : setting the project up

  1. Prepare QGIS

  • Go to Plugins > Manage and Install Plugins…

  • Then, in the search bar at the top left, type QuickMapServices → click Install.

    There is no need to install the old Profile Tool plugin anymore because Elevation Profile is built into QGIS.

  1. Load a Basemap
  • Go to Web > QuickMapServices > OSM > OSM Standard

This appears inside the Web menu after installing QuickMapServices. Use the mouse wheel and the navigation toolbar on the left to zoom to the correct area.

  1. Load the NASA Raster DEM (raster)

  • Go to Plugins > SRTM Downloader This opens the SRTM Downloader window.

  • Set canvas extent is at the top right. It uses whatever is visible on the map.

  • Tick Load image into QGIS when done.

  • Under Output Path, click the folder icon to choose where the file goes.

  • Press Download at the bottom.

Note
  • The first time, the websites asks for NASA Earthdata Login.
  • Use the link to create an account.
  • Once downloaded, the raster DEM appears in the layer panel on the left
  1. Load the TU Delft LAZ file (point cloud)

This opens a file window.

  • After selecting the LAZ file, press Open. You can simply drag and drop it into QGIS.

To style the point cloud:

  • Open the Layer Styling Panel (on the right toolbar, look for the paintbrush icon).
  • Select Attribute by Classification.
  • Set Z as the attribute so colours represent height.

Part 2 : creating the section for analysis

  1. Create the vector line (section line)
  • Go to Layer > Create Layer > New GeoPackage Layer…

On the window:

  • Choose an existing .gpkg file or create a new one.
  • Geometry type = LineString.
  • Create a field called name (text).
  • Press OK. To draw the line: > Go to Layer > Toggle Editing

The editing toolbar becomes active.

  • Use Add Line Feature (icon looks like a bent polyline).
  • Click along the desired path.
  • Double-click to finish.
  • When the attribute window appears, type the line name.
  • then Go to Layer > Save Layer Edits > Go to Layer > Toggle Editing (off)
  1. Use the Elevation Profile tool
  • Go to View > Panels > Elevation Profile

A panel opens on the right side of QGIS.

To add layers:

  • Click + Add Layer at the top of the Elevation Profile panel.
  • Select the NASA DEM and choose Raster type.
  • Select the TU Delft LAZ point cloud and choose Point Cloud type.

To use vector line:

  • Select the line in the map (using the regular Select Features tool).
  • In the Elevation Profile panel, open the menu (the three dots).
  • Choose Generate Profile from Selected Feature.
  1. Adjust the profile view
  • Use Sampling Distance to adjust how detailed the profile is.
  • Use Point Cloud Radius to control how far from the line the point cloud is sampled.
  • Toggle layers on and off using the eye icons.
  • Press Export as Image to save the section graph.
  1. Interpretation
  • The raster DEM gives a smooth representation of terrain.
  • The point cloud shows fine detail like buildings, trees, and surface features.
  • The vector line is the exact path used to extract the profile.

Other sources

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