Use QGIS Maps in Field Surveys with GeoPDF

Introduction

QGIS can create a GeoPDF, a special file format that embeds geospatial (location) information in an ordinary PDF. A GeoPDF has features that are very useful for field surveys and map sharing, such as switching layers on and off and checking your current position with GPS.

This article explains how to create a GeoPDF, step by step, and how to use it. Try creating your own GeoPDF with the powerful features of QGIS.

What you can do with a GeoPDF

A GeoPDF is not just for viewing a map. It also supports GIS-style operations such as the following.

• Check your position and take notes offline: A GeoPDF works with the GPS of a smartphone or tablet, so you can see your current position on it even without an internet connection. As with a regular PDF, you can also write notes directly on it during a field survey.
• Show and hide layers: You can switch the layers set up in the original QGIS project on and off individually inside the PDF.
• View attribute information: You can view the attributes of the features on the map.

Create a GeoPDF in QGIS

This section shows the steps for creating a GeoPDF in QGIS.

First, add layers to QGIS and style them. The example below uses GSI Maps from the Geospatial Information Authority of Japan (GSI) as the basemap, with sample point data for the survey targets on top. The point data was created for this article and differs from real data.

When the map is ready, create a print layout. Here, the layout contains a map item, a legend, a north arrow, and other items.

For details on creating a print layout, see the following article.

Once the print layout is ready, export the GeoPDF. From the menu bar, choose Layout → Export as PDF.

Enter a file name and destination, and click Save. The PDF Export Options dialog opens. Check the following options.

1. Append georeference information: Check this option to embed geospatial (location) information in the PDF.
2. Create Geospatial PDF: Check this option to keep the layer structure in the PDF, so you can show and hide layers and check attributes in a PDF reader.

With both options checked, click Save.

In the layer tree, checking Initially Visible makes that layer visible as soon as you open the PDF. Checking Include Attributes embeds the layer's attribute information in the PDF.

When the export finishes, drag and drop the exported file into QGIS to check that the GeoPDF was created correctly. Because the PDF carries location information, you can see that QGIS adds it as a raster layer, displayed over the other layers.

This article uses a print layout to create the GeoPDF. If a simple map is enough, you can also create one from the menu bar with Project → Import/Export → Export Map to PDF.

Use in field surveys

With smartphone apps that support GeoPDF, such as “GeoPDF mobile” and “Avenza Maps,” you can display the GeoPDF you created above as a background map even without an internet connection, and check your current position using the GPS of your smartphone or tablet.

The example below shows a GeoPDF created in QGIS, transferred to a tablet, and displayed in Avenza Maps. The app shows your current position on the PDF, so you can carry out a field survey with your own map in the background.

If you use an app that lets you write on PDFs, you can also write notes directly on the GeoPDF, just as on a regular PDF. Transfer the PDF back to your PC and open it in QGIS to see the notes together with the map data. Combined with the current position display above, this should make field surveys more efficient.

Control layer visibility and check attributes

Next, this section shows how to use GeoPDF features in a common PDF reader on a PC. The example uses Adobe Acrobat Reader, which is free.

Show and hide layers

First, here is how to show and hide the layers in the PDF.

Click the Layers button on the right.

The Layers panel opens. It lists the layers this PDF contains.

Click the eye icon next to the 調査対象レイヤ layer (survey target layer), and the survey target point layer is hidden in the PDF. In a GeoPDF, you can switch the layers in the PDF on and off like this, which is very handy when you want to look closely at specific layers only.

Check attributes

Next, here is how to check the attributes of a vector layer. In the panel on the right, click the Model Tree button.

The Model Tree panel opens. It shows the layers for which you checked Include Attributes when you exported the GeoPDF.

Expand the 調査対象レイヤ layer to list the features in this print layout. Click a feature, and the attributes of the selected feature appear at the lower right of the screen.

By default, the feature names in the Model Tree are the values in the first column of the attribute table. To show the values of another column, change Display Name in the layer properties before you export the GeoPDF. The Model Tree then shows the values of the column you selected.

Conclusion

This article explained how to create a GeoPDF with QGIS and how to use it. A GeoPDF is a PDF with embedded location information, and it has many advantages, including showing and hiding layers, checking attributes, and working offline.

Use the steps in this article to create your own GeoPDF with QGIS and put it to work in a variety of situations.