Creating maps in QGIS

Having collected all our data, it’s now time to make some maps!

_{Having collected all the raw data on the archaeological sites of Lake Hamrin, now we want to make some maps to display it.}

The first stage is working out how we want to display our site data.

Symbology for polygons

There are lots of ways in which QGIS can display polygons. The best way to use for a particular map will depend on the data being used, the scale of the map, the nature of the background, and what you are trying to communicate! We are going to set out the main options.

Single symbol

The simplest method of mapping polygons is so they all look the same, this is the default symbology when you add a polygon layer to a project.

• 1) Right-click your shapefile in the Layers Panel and select “Properties”.
• 2) Click on the Symbology tab.
• 3) “Single Symbol” should be visible in the first drop-down box by default, but if not select it.
• 4) Select a polygon style from the “Favourites” box in the bottom section of the window.
• 5) Click OK.

_{Selecting a simple “Favourite” style.}

This is a great choice if you need something quick and simple. However, the default favourites are very limited, so we want to have more control over polygon style.

• 6) Open the Symbology properties of your shapefile again.
• 7) Click on one of the simple fills in “Favourites”.
• 8) Then click on “Simple Fill” towards the top of the window.

This opens plenty of options that we can customise to our liking. We can change the fill colour, the stroke (outline) colour and thickness. We can also change the fill style, if we want something other than a normal block of colour, and the stroke style, if we want a dashed or dotted line instead of a solid line.

_{All these instructions also apply to point and line features, line features just won’t have a “fill” colour.}

_{Customising the polygon style.}

Categorized symbology

• 1) Open the Symbology properties of your shapefile.
• 2) In the first drop-down list select “Categorized”.
• 3) For the “Value” field select the field you wish to base your symbology on.
• 4) Click the “Classify” button towards the bottom of the window.

_{It is best to only select fields that use between two and ten categories. For example, you would not want to categorise using “site name” as the value would be different for every site.}

• 5) Change the base style by clicking the “Symbol” box.
• 6) You can now change the style for each category individually, or you can select a colour ramp to change all the styles automatically (like a raster, see Week 4.6).
• 7) You can also drag and drop the categories to order them differently to the alphabetical default.
• 8) You can also untick or remove “all other values” (assuming you have collected data for all your sites for your chosen category).
• 9) Click OK.

_{Changing polygon category styles.}

_{An example of a useful polygon category symbology.}

Graduated symbology

• 1) Open the Symbology properties of your shapefile.
• 2) In the first drop-down list select “Graduated”.
• 3) For the “Value” field select the field you wish to base your symbology on.
• 4) Click the “Classify” button towards the bottom of the window.

• 5) Change the base symbology and alter the category symbology as for a categorised symbology.
• 6) You can increase or decrease the number of options by changing the “Classes” number.

_{Graduated polygon symbology.}

Centroid fill

• 1) In your Graduated or Categorised symbology click the “Symbol” box.
• 2) Click “Simple fill” in the window that pops up, or just “Simple fill” if you are using a single symbology.
• 3) Change “Symbol layer type” to “Centroid Fill”.
• 4) Click “Marker” to change the size of the point, or “Simple marker” if you want more options.

_{A centroid fill is a great way of conveying information for lots of polygons of different sizes – smaller sites are much easier to see as points.}

Labels

• 1) Right-click your shapefile in the Layers Panel and select the “Labels” tab.
• 2) Change “No labels” to “Single Labels”.
• 3) Change “Value” to the field you wish to use for your labels, usually the site name or number.
• 4) Click OK.

_{Adding basic labels to your sites.}

_{Labels have been added for our sites, but they are difficult to read.}

Label font

_{Changing the label font.}

_{Adding a label buffer.}

_{Changing the label placement.}

_{Adding a buffer and changing the font and placement has greatly improved the labels.}

_{Trying to fit all the sites names onto this map is a bad idea – it makes it hard to see the sites!}

Selecting the right background

_{Satellite imagery can be used as a background to your map.}

_{A DEM might work better if your sites use different colours.}

_{A semi-transparent hillshade can be used to tone down satellite imagery.}

• 1) Right-click your image in the Layer Panel and select “Properties”.
• 2) Select the “Transparency” tab.
• 3) Drag the transparency slider down to around 50%.
• 4) Click OK.

_{Satellite imagery can also be made semi-transparent to give a similar effect.}

Making a map

• A north arrow to show the orientation of the map.
• A scale bar to show the scale.
• A legend or key if your sites use different colours or symbols.

_{This map showing the planned construction of a new road near Stonehenge is a great example of a good map – note the north arrow, scale bar and legend. Courtesy of the Stonehenge Alliance.}

Print layouts

• 1) On the Main Menu navigate to “Project” > “Import/Export” > “Export Map to Image”

• 2) On the Main Menu navigate to “Project” > “New Print Layout”.
• 3) Give your layout a name, for example “map 1”.

_{The Print Layout window.}

Adding map elements

• 1) Navigate to “Add Item” > “Add Map” on the menu, you can also press the “Add Map” button on the side toolbar.
• 2) Click and drag to create a rectangle for your map – it should fill most of the page.

_{Adding a map to your layout.}

• 3) Click on the map box and then click the “Adjust map content” button.
• 4) Click and drag to adjust the position and use the mouse wheel to adjust the scale.
• 5) Fine tune the scale by clicking the “Item Properties” tab and altering the scale value.

_{You can adjust the position and scale of the map.}

• 6) Navigate to “Add Item” > “Add North Arrow” on the menu or use the toolbar button.
• 7) Click and drag to create a north arrow on your map.
• 8) Click on it and resize and reposition it to get it in the right place.

_{Adding a north arrow.}

• 9) Follow the same process for a scale bar.
• 10) You can adjust the scale bar’s units and the number of segments in the “Item Properties” tab.

_{Adding a scale bar.}

• 11) Add a legend to your map using the same process.

• 12) Click on the legend and select the “Item Properties” tab.
• 13) Untick “Auto update”.
• 14) Click on an item you wish to remove and click the red “Remove” button.
• 15) Repeat until you have just the layers you want in your legend.

_{Customising the legend.}

• 16) You can adjust any text in your legend by double clicking it and editing it.
• 17) You can add a legend title at the top of the “Item Properties” tab.
• 18) You can add a frame by scrolling down and ticking the “Frame” box.

_{Adding a title and frame to the legend.}

_{Other annotations can be added in a similar way.}

Exporting maps as images

• 1) On the menu navigate to “Layout” > “Export as Image”.
• 2) Save your map somewhere suitable and give the image a name.
• 3) Set “Export resolution” to 300 dpi.
• 4) Tick “Crop to Content” and click “Save”.

_{Map image export options.}

• 5) On the main QGIS window click the green link that pops up above the Map Window.

_{Click the green link.}

_{Our final map has been exported. SRTM data courtesy of the USGS.}

_{Are you pleased with your map? Did you add an extra useful annotations?}