8  Lab 8: Making Maps - Part II

In this lab we will continue working on our map of the Bamburgh Castle region, this time focusing on manually digitizing polygons, labelling, and finishing our actual map page layout.

Warning

To complete this lab, you must watch the practical videos on how to manually digitise features in QGIS, which are available on the Week 4 prep page on Canvas

8.1 Getting Ready

Make sure you restore the project folder and files you created in the previous lab, and then open your project.

8.2 Guided Exercise 1 - Digitizing the castle

One thing that seems to be missing from our map is more emphasis on the castle’s location. Let us use the aerial photo we acquired to digitize the castle area.

  1. Add to your project the aerial orthophoto you downloaded at the start of the previous lab. If you had a wide selection and downloaded multiple tiles, the correct file is nu1835_rgb_250_03.jpg. It may be that the photo comes without a CRS defined (a question mark icon will appear to the right of the layer name). If that happens, just right click on the layer name, and select Layer CRS > Set Layer CRS to pick EPSG:27700.
Stop and Think

Why did we use Set Layer CRS and not Reproject?

In this case, we know the aerial photo uses the EPSG:27700 CRS (by looking at the metadata, and also by knowing that any UK official cartographic product uses it). It is just a matter of informing QGIS what the CRS is, as it was not properly detected when the layer was added to the project. We use Reproject when the layer already has a defined CRS, and we want to change it to a different CRS (meaning likely a different datum, projection and maybe even a different coordinate type - such as from degrees to meters), and thus we need to transform (i.e. calculate) a new set of coordinates.

  1. Now we need a new empty layer to digitise on. Click on the New shapefile layer button ( ) on the main QGIS toolbar. You will get the New Shapefile Layer window:

  1. First pick a folder to save your file and name it bamburgh_castle, on the File Name box. Then for Geometry type, pick Polygon, and pick EPSG:27700 for the CRS. Notice how QGIS automatically creates an integer attribute named id. We want a text attribute to hold the castle name, though, so enter name as the name of the field on the New Field options, then pick the Text (string) data type and a length of 80 (the default) and click on Add to Fields List. You should see the new name field added to the fields list. Then click OK.

  2. Find your new layer on the Layer Panel. It doesn’t have any geometries yet, so you won’t see anything on your map. Highlight your new layer, and then put it into editing mode by clicking on the Toggle Editing button () on the main QGIS toolbar. Make sure you are editing the right layer (it should have a pencil symbol on top of the symbology colour on the layer list).

  3. Now right-click on the aerial photo layer and select Zoom to Layer(s) to centre the map canvas on it. Then manually set a scale of 1:1500 on the bottom QGIS bar. It is important to be aware of the scale you are digitizing at, and keep it constant so that the level of detail is also constant. Drag the castle to the middle of the canvas using the Pan Map tool (the hand).

  4. Now highlight the new shapefile layer (which is being edited) again. The Digitizing tools toolbar () should be available. Click on the Add Polygon Feature button () to enter a polygon drawing mode. Start clicking anywhere in the castle outer walls, and then keep clicking to trace the entire castle shape. Once you finish you polygon, right-click to end the drawing. A window will pop-up asking you to enter an id and name. Enter 1 and Bamburgh Castle respectively.

  5. If you want to edit the polygon shape after the fact, use the Vertex Tool (). Then click once on a vertex to select it, and then cick again to reposition it, or the Delete key on your keyboard to delete it. You can also add a new vertex by hovering the mouse in between vertices until you see a red x. You should end up with something like this:

  1. Once you’re happy with your polygon, remember to click the Save Layer Edits button (on the editing toolbar - not the Save project button) and then exit editing mode. Set you map back to the 1:80000 scale you decided on in the previous lab, and pick a strong and visible colour for the castle polygon. Turn off the aerial image again, and save your project.

8.3 Guided Exercise 2 - Adding places and labels

No good map is complete without the addition of informative labels, which help add context and reference. QGIS has very powerful labelling features (which we will only lightly explore), but you should always spend some good effort on labelling - it often turns a good map into a great map.

Stop and Think

When should I use labels and when should I use the map legend to name things?

As a rule of thumb, legend names indicate categories or groups of things, as well as continuous variables. Labels identify unique things. For example, if there were multiple castles in the map, you could have a legend symbol indicating “castle” (a category of thing), and then labels showing the names of each castle. If you wanted to indicate a specific mountain peak in your elevation map, you would still have an “Elevation” item on the legend explaining the elevation symbology (a continuous variable), and then a point symbol and a label to identify the particular peak. If there were multiple peaks, then you would add a “Mountain Peak” item to the legend, associated with the point symbol you selected to indicate peaks. But this is not essential when there is only a single item in the category (like our single castle).

  1. Right click on the castle layer you created and go to Properties > Labels. Change the No Labels box to Single Labels, to reveal several options. For Value, pick the name attribute, which contains our layer name. On the Text sub-tab, increase the font size to 14, and on the Buffer sub-tab, click on Draw Text Buffer. Click on Apply, and you should get a label like in the figure below:

  1. The label is however hiding the actual castle polygon. So return to Properties > Labels and go to the Placement sub-tab, change the Mode to Outside Polygons, and set Distance to 1 millimetre. The label should move to the right of the polygon now.

Next, let us add some named places to the map, to help with navigation. For that we will use another layer from the Vector Map District OS database we downloaded, the NU_Named_Place layer.

  1. Add the NU_NamedPlace.shp layer to your project. You will see a large number of points appear, probably too many to look good. But this dataset has information on the type of place (CLASSIFICA) and an indication of place importance (FONTHEIGHT), that we could use to reduce the number of points.
Stop and Think

  1. How would you reduce the number of points show based on the above attributes?

  2. Why do the attributes have truncated names such as CLASSIFICA?

  1. You could go to the attribute table and use Select by expression to select the specific combination of attributes you wanted. But we will learn a different way below.

  2. Because shapefile is a very old format, back when memory and storage were very limited. So they have an imposed limitation of ten characters as the maximum length of a field name - if you create a new field on a .shp file and name it something longer than 10 characters, the name will be cut-off at the tenth character. Geopackages don’t have that restriction.

If we want to limit the number of features that are available to us in a layer, we can use the Filter method instead ofSelect by Expression. While selecting is useful to create a selection that you can then export or summarise, filtering will essentially hide the information from view and manipulation - as if it didn’t exist. Let us filter our named places to only medium and large populated places.

  1. Right click on the NU_namedPlace layer and select Filter.... You will see a new window similar to the Select by Expression window. On this window, you can pick attributes on the top left, and then list all unique values of each attribute in the top right (select the attribute then click onAll). You can then double click on attribute names, values and operators, or simply type your expression in the bottom window. For this dataset, we want to filter using the following expression: "CLASSIFICA" = 'Populated Place' AND ("FONTHEIGHT" = 'Medium' OR "FONTHEIGHT" = 'Large'). Notice the parentheses! Then click on OK.

Stop and Think

Why do we use a set of parentheses to encapsulate the OR statement in the expression above?

Boolean operators are processed as mathematical operations, from left to right. So if we typed "CLASSIFICA" = 'Populated Place' AND "FONTHEIGHT" = 'Medium' OR "FONTHEIGHT" = 'Large' without parentheses, QGIS would first look for the features that are a populated place and medium, and then try to find large places within this first selection. But we want for it to first find all medium or large places and then from these pick only the ones that are also (the AND) populated places. As with maths, the parentheses ensure we solve the OR first.

You should now have a lot fewer Named Places scattered through the map, and if you inspect the attribute table, you will see only the filtered results. It is as if the rest of the data doesn’t exist! You will always know if a layer is being filtered by the ‘funnel’ symbol to the right of the layer name (and you can click on the symbol to edit or clear the filter).

  1. Now follow the same procedure you used to label Bamburgh Castle to label the populated places, using the DISTNAME attribute - but use a font size of 10 to keep the visual hierarchy in relation to the castle, and keep the Placement option as the default Cartographic option.

  2. Change the Symbology of the NU_NamedPlaces layer to the preset symbol topo pop capital (a white circle with a black dot in the middle), with a Size of 2.4.

  3. Add the NU_RailwayStation.shp file to your map, and label it using the DISTNAME attribute as well (you should see only one station, ‘Chathill’). Make the label size 10, colour it blue and make its style bold italic; do not use a buffer this time.

  4. Now go to the Symbology tab for the railway station layer, and pick Single Symbol. Select the Simple Marker sub-item, and then change the Symbol layer type from Simple Marker to SVG Marker. SVG stands for ‘Scalable Vector Graphics’ and is a commonly used format to store figures in desktop publishing.

  5. Once you change the Symbol layer type, a new SVG Browser section will appear below. In there, find the transport folder on the browser to the left, and pick the railway symbol (looks like a train). Then above it, change the Fill Color to the same blue you used for the label, and decrease the Stroke Width until it says No stroke. Increase the size of the symbol to 6 (width and height should be linked by default). Your options should look like this (stroke colour doesn’t matter):

Good job with labelling! Your map should now be looking like this:

  1. Save your project.

8.4 Guided Exercise 3 - Laying out the final map

We have now added everything we want to our map, and styled and labelled it properly. Now it is time to work on the final page layout for our map. This is where we add the critical cartographic elements that turn a figure into a map (legend, scale, graticule, north arrow), and include some map insets and annotations to facilitate map interpretation.

8.4.1 The Legend

The map legend is the most important cartographic element, as it associates meaning to all the visual variables (colours, symbols, sizes, patterns) you have used on your map. QGIS has a handy tool to generate the legend automatically, but we should always tweak the end results to improve map readability.

  1. Go to the menu Project > Layouts and pick the layout you created in the previous lab, when you were deciding on the scale and coverage of your map. The Layout editor window will launch separately from the main QGIS window.

  2. Either go to the menu Add Item > Add Legend or click the Add Legend button () on the vertical toolbar to the right. The cursor will turn into a cross. Then click and drag to create a legend on the lower right corner of the page. It will look to big and go outside the page - don’t worry, we will fix it next.

  1. The first thing we will do is clean up the legend. By default QGIS will add all active layers to the legend. Select the Legend item on the top left of the Layout window (under Items), and then select the Item Properties tab on the bottom right.

  2. First set the name of the legend as Legend (type it on the box). Then uncheck the Auto Update option, and start removing items by selecting them and clicking on the red ‘minus’ button at the bottom of the layer list. You want to end up with a legend like the one below (use the green ‘plus’ button to add a layer back if you remove it by mistake):

  1. In my case, I also used the same symbology for Primary Road and Primary Road Collapsed Dual Carriageway, so no need to have both in the legend. Again, I can expand the NU_Road_clip layer on the legend layer list, select only the Primary Road Collapsed Dual Carriageway item and remove it with the red minus button.

  2. For the OS_50_DEM_NU layer, we don’t need the Band 1(Grey) sub-name, so remove it as well. The legend should now be looking like this:

  1. This legend is occupying a lot of space in our map. Scroll down past the layer list on the legend Item Properties, until you find the option Fonts and Text Formatting. Expand it by clicking on the arrow, and then reduce the font sizes of the several options by 4 points. To do that, click on the down-arrow to the right of each Font box, and change the font size at the top of the menu.

  1. The spacing between items seems to be excessive now, so find the Spacing option for the Legend item and reduce all non-zero spacing by 1mm, except for the Column Space option - set that one to 3. It will have an effect later.

Our legend is looking much better, but there is a big problem: the item names reflect the file names, and your map readers won’t know what NU_NamedPlace means. So we should rename our layers to have intelligible names. You can rename your layers in the Map Layout by going back to the legend Item Properties and double clicking each item. But I think it is a better idea to rename the actual layers in the QGIS project. This way, if you decide to add/remove other layers to the legend, you won’t need to rename then again.

  1. Go back to the main QGIS window, and rename all the layers in the legend to proper, readable names. For example, NU_RailwayStation to Railway Station, NU_NamedPlace to City/Town, etc. Try to use short names:

  1. Now that we have nice and short names, we can also save space by breaking the legend into columns. Go back to the Layout editor, and on the Legend Item Properties find the Columns option and increase Count to 2. Your legend should now have two columns, spaced 3mm (remember the Column Space option you set a few steps above?)

  2. The extra space gives us the chance to expand our elevation bar a bit. Go back to the list of legend layers in the Legend Item Properties, and double click on the Elevation colour bar. Leave the Width as default, and set the height to 20. Also add m as the Suffix so we have clearly labelled units. Your final legend should now look like this:

  1. Save your layout.

8.4.2 Adding a scale bar

Every proper map needs a scale bar. Luckily, since all data in QGIS is georeferenced, the Map Layout editor can automatically calculate the correct size for indicating scaled distances in our map.

  1. Go to the menu Add Item > Add Scale Bar, or click the Add Scale Bar button (), and drag a box to add a scale to the top left of the map area, over the ‘ocean’.
Tip

We want to make sure the cartographic elements do not cover information on the map. Because we have a large plain ocean area in this map, which is not of much interest, it is OK to add the scale bar there. But if the map had relevant info throughout, it would be better to place the scale outside the map area.

  1. Repeat this process and add a second scale bar below the first. Then select one of the scale bars on the Items list, and then on its Item Properties change the units from Kilometers to Miles. We now made our map accessible to both civilized and barbarian people metric and imperial thinkers.
Tip

Feel free to play with the Style, Segments and other Item Properties of your scale bars to tailor them to your taste.

  1. Save your layout.

8.4.3 Adding a Graticule

The graticule (coordinate grid) is another essential cartographic element - without it our map is not showing proper spatial information. A good graticule facilitates navigation without obscuring the map elements. Let us add a graticule to our map:

  1. On the Items list, select the Map 1 object. That is your main map frame. Go to its Item Properties and find the Grids option. Expand it and click on the green plus button to create a new graticule, which will show up below it as Grid 1.

  2. Select Grid 1 and click on Modify Grid. A new set of options will appear:

  1. We will set several options here to have a nice grid. First, we need to decide our Interval in the X and Y directions. This is the spacing between coordinate lines. We are using the OSGB CRS (EPSG:27700) with metric coordinates, so this interval will be in meters. Let us add coordinates every 5km by changing both X and Y spacing to 5000. You should now see a grid of lines in the map.

  2. The squares formed by the lines seem a bit ‘offset’ in relation to the map area. We can shift them so they are nicely centred in the vertical and horizontal direction by adding X and Y offsets. On my map, an X offset of 500 and a Y offset of -1500 centres the grid nicely. You may need to use different values depending on your choice of framing.

  3. I now have coordinate lines, but they have no coordinate numbers, thus so far my grid is useless. Next set the Frame Style option to Exterior Ticks, then keep scrolling down until you reach the Draw Coordinates option. Check the box and coordinate numbers will appear at each line. But they do not align well with the frame, and also have useless decimal places.

  4. Our coordinates also have no axis indication, so change the Format option from Decimal to Decimal with Suffix. That will add the easting (E) and Northing(N) indicators.

  5. Below Draw Coordinates, you see sets of options labelled Left, Right, Top and Bottom. Change the third option for Left from Horizontal to Vertical Ascending, and for Right to Vertical Descending. Then at the bottom of the Draw Coordinates section, set Coordinate Precision to 0 to remove the decimal places.

  6. If we expected our map users to navigate using a compass, the actual grid lines would be useful. But since this is unlikely, the actual black grid lines are too obtrusive. Go back to the top of the Map Grid Properties, and change the Grid Type from Solid to Frame and Annotations Only.

  7. Finally, let us add a black border to our map for aesthetic purposes. Go back to the main Item Properties for Map 1, and find the Frame option. Enable the checkbox to add a frame. Save your layout.

My map layout is now looking like this:

8.4.4 Adding a North Arrow

A North Arrow is only strictly necessary if your longitude grid lines are not parallel, but we will add one so you know how (and make sure you show us you’ve learned how on the assessment!).

  1. Go to the menu Add Item > Add North Arrow or click on the Add North Arrow button (can you spot it?), and drag the mouse where you want your North arrow to be. It is by convention usually placed on the top left corner, so I’ll move the scale bars a little to the left and then place my arrow there.

  2. If you select the North Arrow item and go to its Item Properties you will see there are many SVG symbols for north arrows, in the arrows and wind roses folders. Pick any one you like. Save your layout.

8.5 Guided Exercise 4 - Adding map annotations

Annotations help our readers understand the map. The main piece of annotation any standalone map should have is a title (you can omit the title if your map is a figure in a document, where there will be an explanatory caption under it). We also want to add some information such as data sources, map author, the CRS used and the map scale.

  1. Add an annotation frame under the map legend using Add Item > Add Label or the Add Label button (). On the Item Properties for your new label, you will see a text box saying Lorem Ipsum. These are two words in Latin from a text passage that has historically been used by designers to indicate placeholder text (see lorem ipsum). Replace the Lorem Ipsum by the following text, including the line breaks and line spaces:

EPSG:27700

1:80000

Author: (your student number)

Data source: Digimap 2024

  1. Under the text box, select Center for Horizontal Alignment, and set font size to 8. Then move your legend up until you can fit this annotation under it.

  2. Now add a Map title, using the same Text Label tool, such as Bamburgh Castle - Northumberland, UK. You may want to resize your main map frame a bit to make room for the title above it. Set it to bold and font size 14.

My map now looks like this:

  1. Save your layout.

8.6 Guided Exercise 5 - Adding map insets

A common element of maps that aids map use is the inclusion of map insets, ‘sub maps’ that show either a portion of the main map in higher detail or the location of the main map on a broader scale map. We will add both to our design

  1. Insert a new map area on the top left corner of your layout using the Add Map () button. It will by default be named as Map 2 on the Items list:

  1. Before we move forward, let us rename our map items to make our work easier. Double-click on Map 1 in the Items list and rename it to Main Map, then double-click on Map 2 and rename it to Overview Map. Save your layout.

For now our overview map shows the exact same content as the main map - the maps are by default tied to the QGIS main window. To be able to show separate maps, we need to associate each map with a QGIS theme. We will do this now.

  1. First, go back to the main QGIS window, and add the GB_Overview_Plus.tif file to your layers. Turn its visibility off.

  2. Now make sure all (and only) the layers you want to be visible on the main map are on, and the others are off. Then click on the small ‘eye’ button on the top of the Layers panel, and click on Add Theme. Name your theme Main Map.

  3. Now turn off all layers except the GB Overview Layer, and repeat the steps above to create an Overview theme.

  4. Click again on the ‘eye’ button and select the Main Map theme. It will revert to the selection of layers you had turned on when you created the theme. Themes are a useful way to have shortcuts to different sets of visible layers.

Tip

If you need to change an existing theme, activate/deactivate the layers you want, and then click on the eye button and select Replace Theme.

  1. Now go back to the Layout Editor window, and select the Main Map item. On its Item Properties, find the Layers option and enable the Follow Map Theme option, picking the Main Maptheme. Then do the same with the Overview Map, and set it to the Overview theme.

  2. Set the scale of the overview map (on its Item Properties) to 5000000 (five million), and use the Move item content () tool so that Newcastle is about centred on the map. This map has ‘painted-on’ labels, so make sure you don’t cut off any labels when placing your map.

Now we need to indicate ‘where’ in the overview map is the main map located. QGIS has a nice feature to do that for us automatically:

  1. Go to the Item Options of the Overview Map and find the Overviews option. Expand it and click on the green plus symbol to add an overview. Select the newly created Overview 1, and on the Map Frame option below it, select Main Map. You should now see a transparent pink box indicating the location and coverage of the Main Map on the Overview map inset.

The map should now look like this:

8.7 Independent Exercise 1 - Adding a second coordinate grid and a second inset map

  1. Now add a coordinate grid to the Overview map. following the same steps as you did for the main map, but with the following changes:

  • Instead of the OSGB CRS, use WGS84 as the CRS, so that the coordinates are in degrees (to determine ‘where in the world’ somewhere is, degrees make more sense than meters). To do that, manually pick EPSG:4326 as the CRS on the Map Grid Properties of the new grid.

  • Use Frame and Annotations Only as for the Main Map, but this time we want coordinates and ticks just on the top and right of the map. So under the Frame options uncheck the Bottom side and Left side boxes, and on the Draw Coordinates section, change the first option of Bottom and Left from Show all to Disabled.

  • Make the font size 8, make the coordinates on the right Vertical Descending, and get rid of the unnecessary decimal places (i.e. the zeroes).

  • Set the Overview map Frame option to on.

The final Overview map should look like this:

  1. Now add a second inset map showing the aerial photo view of the castle. Follow the steps used for the Overview map, with the following changes:

  • Create a third theme on QGIS, where only the air photo is visible, and name it Close Up.

  • Add a new map frame in the space left between the Overview map and the Legend, rename it from Map 3 to Close Up, and set it to follow the Close Up theme.

  • Adjust this inset map scale to show all of the castle as close up as possible. Around 15000 should work well.

  • Do not add a coordinate grid to this map inset, but do add a Scale Bar. To make the scale relative to the Close Up map, create the scale bar then go to its Item Properties, and on the first option called Map, make sure it is set to Close Up Map. Make the scale only one segment long, and place it within the close up image.

  • Add a small text below the Close Up Map, saying Aerial View of Bamburgh Castle.

Your final map should look like this:

8.8 Independent Exercise 2 - Exporting your map

Your map is done! Now all is left is to export it. Your main choices are to export it as an image (to add it in a report or similar), or as a PDF if you want the map to be a standalone file.

  • To export as an image, on the Layout Editor window go to Layout > Export as Image.... Pick a folder and file name to save it, and then it will show you some options. You can normally use the default options, or check the Crop to Content box if you want your image edges to cover only the content of the map (i.e. no white margins).

  • To export as a PDF, go to Layout > Export as PDF.... Pick a folder and file name to save it, and then it will show you some options as well. The defaults are fine for most cases.

Well done! You havemade a very complex and (arguably) nice looking map! You are now ready to take on the first module Assessment, and make a beautiful map showing the not-so-beautiful issue of deforestation in the Amazon.