Lab 1: Introduction to QGIS — Being John Snow

Turn-in for grading: This lab includes material that must be turned in for grading. Complete the required deliverables and submit them as instructed by the course.

The Broad Street Outbreak: A Story of Spatial Thinking

In late August 1854, a devastating cholera outbreak erupted in the Soho neighborhood of London. Within three days, 127 people were dead. Within a week, three-quarters of the residents had fled the area, and the death toll would eventually climb to over 600.

At the time, the prevailing scientific theory — known as miasma theory — held that diseases like cholera were caused by "bad air" rising from rotting organic matter. Most physicians and public health officials believed that the foul smells of London's overcrowded neighborhoods were themselves the cause of illness. Under this theory, the solution was better ventilation and sanitation of the air, not the water.

Dr. John Snow, a physician and one of the founders of modern epidemiology, was skeptical. He had already published a paper in 1849 arguing that cholera was transmitted through contaminated water, but the medical establishment was unconvinced. The Broad Street outbreak gave him an opportunity to gather evidence.

Snow began by doing something deceptively simple: he made a map. He went door to door in the Soho neighborhood, recording the address and number of deaths at each household. He then plotted these locations on a map of the neighborhood alongside the locations of the public water pumps that served the area. The spatial pattern was striking — the deaths clustered tightly around a single pump at the intersection of Broad Street and Cambridge Street (now Broadwick and Lexington Streets).

But Snow didn't work alone. Reverend Henry Whitehead, the curate of St. Luke's Church in Soho, initially set out to disprove Snow's water theory. Whitehead knew the neighborhood intimately — he had visited hundreds of parishioners during the outbreak — and he was skeptical that a single pump could be responsible. However, as Whitehead conducted his own investigation, interviewing families and tracing the movements of victims, his evidence increasingly supported Snow's hypothesis.

Whitehead made a critical discovery: he identified what was likely the index case — a baby (at what is now The John Snow Pub at 43 Broad Street) whose soiled diapers had been emptied into a cesspool just three feet from the Broad Street pump well. The cesspool's brick lining had decayed, allowing sewage to seep into the well water. This was the spatial connection between the source of contamination and the deaths that Snow's map had revealed.

Together, Snow's spatial analysis and Whitehead's ground-level detective work convinced the local Board of Guardians to remove the handle of the Broad Street pump on September 8, 1854. The outbreak was already waning by then — most residents had fled — but their combined investigation became one of the founding examples of epidemiology and spatial analysis. It demonstrated that where something happens can be the key to understanding why it happens.

In this lab, you will retrace Snow's steps using modern GIS tools: plotting death addresses, mapping pump locations, and using spatial analysis to determine which pump was associated with the most deaths.

Background Viewing: Steven Johnson's TED Talk — How the "Ghost Map" Helped End a Killer Disease

Overview

Along the way, you will practice the fundamental skills of working with a desktop GIS:

  • Opening and saving a QGIS project
  • Adding and styling data layers (vector, raster, and CSV)
  • Understanding coordinate reference systems (CRS)
  • Performing basic spatial analysis (spatial mean)

Setup

Before starting this lab, you should have already completed the Week 00 setup materials:

Data

Download the data package from: https://github.com/mapninja/Earthsys144/blob/86e25f6d3ccfe42a312c920b002abb6819fa2cd9/data/Being_John_Snow.zip

Extract the zip file and place it in your local GIS working folder (remember — not in a cloud-synced folder like iCloud, OneDrive, or Dropbox! See the Week 00 guide if you need a reminder about why).

The project data folder contains the following datasets:

  • deathAddresses.csv — A table of latitude and longitude coordinates for addresses affected by the cholera outbreak. This table also contains the number of deaths at each address. This is an example of tabular data with embedded spatial information — it's not a spatial format by itself, but we can turn it into one using the coordinate columns.
  • Water_Pumps.geojson — A GeoJSON file containing the locations of all 13 water pumps from Snow's original map. As you learned in Week 00, GeoJSON is a single-file spatial format (unlike shapefiles), which makes it convenient for sharing.
  • John_Snow_Map.tif — A georeferenced image of the map from John Snow's original report on the cholera outbreak of 1854. Georeferencing means that real-world coordinates have already been assigned to this image, so QGIS knows exactly where on Earth it belongs.
  • Study_Area.shp — A rectangular polygon that describes our area of interest. This is a shapefile, which as you learned in Week 00, is actually a collection of multiple files (.shp, .shx, .dbf, .prj, etc.) that must stay together in the same folder.

Getting Started on a Project

In this section you will create a new QGIS project, get oriented to the interface, add a basemap, and load your first data layer.

Create a Map Document

  1. Open QGIS. If you set up a custom User Profile during Week 00, make sure you are using it (Settings > User Profiles).
  2. Save the empty project to the top level of your data folder (the one you extracted the zip into), using Project > Save As. Name it something meaningful like SnowMap.qgz or Cholera_Map.qgz.

What is a .qgz file? As you learned in Week 00, a QGIS project file is very small (usually under 1 MB). It does not contain your actual data — it only stores references to where your data files are on disk, plus your styling and layout choices. This is why keeping your .qgz file and your data folder together is so important.

Notice that when you save your map document, a new item called Project Home appears in the Browser panel. This is a shortcut to the folder containing your project file — you'll use it frequently to find your data.

The QGIS Interface

Here is a quick refresher on the three main parts of the QGIS interface:

The Map Canvas — This is the large central area where your data is visualized. As you add layers, change their styling (symbology), or reorder them, the map canvas updates to reflect those changes.

Panels (docked on the sides):

  • Browser Panel — A file explorer for navigating your drives and finding data to add to your project.
  • Layers Panel — Lists all the data layers currently loaded in your project. The order matters: layers at the top are drawn on top of layers below them.
  • Layer Styling Panel — A quick way to change how a layer looks (colors, symbols, labels) without opening the full Properties dialog. Enable it from View > Panels > Layer Styling.

Toolbars (across the top):

  • Project — New, Open, Save, Save As, and Print Layout tools.
  • Map Navigation — Pan, Zoom In/Out, Zoom to Full Extent, Zoom to Layer, and Refresh.
  • Attributes — Identify features, open the attribute table, measure distances/areas, and manage spatial bookmarks.
  • Data Source Manager — Add vector, raster, or delimited text layers.
  • Editing — Tools for creating and modifying features. These are grayed out until you start an edit session.
  • Selection — Select or deselect features by clicking, by attribute value, or by spatial location.

Tip: You can show or hide any toolbar or panel by right-clicking in the toolbar area, or from the View menu.

Customize the Interface

The default QGIS layout includes many toolbars that you may not need right away. You can rearrange the interface by dragging the dotted handles on toolbars or the title bars of panels. You can also toggle panels and toolbars on and off from View > Panels and View > Toolbars.

  1. Rearrange your toolbars and panels until your QGIS interface is comfortable to work with. A clean layout might look something like this:

Add a Basemap

A basemap is a background reference map (streets, satellite imagery, terrain, etc.) that gives geographic context to your data. We will use the QuickMapServices plugin to add one.

If you already installed QuickMapServices and downloaded the contributed pack during Week 00, skip to step 4. Otherwise:

  1. Go to Plugins > Manage and Install Plugins, search for QuickMapServices, and click Install Plugin.
  2. Go to Web > QuickMapServices > Settings, select the More Services tab, and click Get contributed pack.
  3. Click Save to close the Settings dialog.
  4. Go to Web > QuickMapServices > CartoDB > Stamen Toner Lite to add a simple black-and-white basemap.
  5. Save your project.

What is a basemap service? Unlike the data files on your hard drive, a basemap is streamed from the internet as a set of pre-rendered image tiles. You can see it but you can't edit it or query its attributes. It's purely for visual reference.

Add the Study Area Layer

Now we'll add our first real data layer — a shapefile that defines our study area in the Soho neighborhood of London.

Reminder: A shapefile is actually a bundle of files (.shp, .shx, .dbf, .prj, etc.) that must stay together in the same folder. You only need to open the .shp file — QGIS will find the others automatically. See Introduction to Spatial Data Formats for more detail.

  1. In the Browser panel, find the data folder for this lab (look for Project Home) and double-click on Study_Area.shp to add it to your project.

  2. In the Layers panel, right-click on Study_Area and select Zoom to Layer.

  3. Open the Layer Styling panel (if not already visible, enable it from View > Panels > Layer Styling), or click on the Styling Icon

  4. In the Layer Styling panel, click on Simple Fill, then change the Fill style to No Brush so the polygon is just an outline. Optionally adjust the Stroke color and Stroke width to make it stand out against the basemap.

  5. Save your project.

Explore Navigation Tools

The Map Navigation Toolbar provides the main tools for moving around the Map Canvas. Take a moment to try each one:

Tool Name What it does
Pan Map Click and drag to move around the map without changing the zoom level.
Pan to Selection Centers the map on the currently selected feature(s).
Zoom In / Zoom Out Click or drag a box to zoom. You can also use your scroll wheel.
Zoom Full Zooms out to show all layers. (This sometimes zooms too far out if you have a global basemap loaded.)
Zoom to Selection Zooms to fit the currently selected feature(s) in the canvas.
Zoom to Layer Zooms to fit a specific layer's extent.
Zoom Last / Zoom Next Undo/redo your zoom and pan history — very useful if you accidentally zoom to the wrong place.
Refresh Redraws the map canvas.

Keyboard shortcut: You can also pan by holding the spacebar and dragging, and zoom with your scroll wheel, regardless of which tool is active.

Understanding Map Scale

As you zoom in and out, notice the Scale value displayed at the bottom of the QGIS window (e.g., 1:10,000). This ratio tells you the relationship between a distance on screen and the real-world distance it represents.

  • 1:1,000 means 1 cm on screen = 1,000 cm (10 m) in the real world — this is a large scale (zoomed in, showing a small area in great detail).
  • 1:1,000,000 means 1 cm on screen = 10 km in the real world — this is a small scale (zoomed out, showing a large area with less detail).

The naming is counterintuitive: large scale = small area. Think of it this way: on a large-scale map, the features themselves appear large.

Spatial Bookmarks

Spatial bookmarks save a specific map extent (location + zoom level) so you can return to it quickly. This is useful when you need to zoom around the map but want to snap back to your study area.

  1. Right-click in any empty area of the toolbar and enable the Spatial Bookmarks panel.
  2. Right-click on your Study_Area layer in the Layers Panel and select Zoom to Layer.

  3. In the Spatial Bookmarks panel, click Add Bookmark and name it SOHO, and save it in your Project Bookmarks.

  4. Now use your Scroll Wheel or the Zoom Out tool to zoom out to the world. Then use the Zoom to Bookmark button to jump back to your study area — much faster than panning and zooming manually.

Working with Coordinate Reference Systems (CRS)

Every spatial dataset has a Coordinate Reference System (CRS) that defines how its coordinates map to locations on Earth. Each CRS is identified by an EPSG code — a unique numeric identifier (e.g., EPSG:4326 for standard latitude/longitude). If this concept is fuzzy, review the CRS section above in this lab.

In QGIS, the Project CRS controls how all layers are displayed on screen. QGIS can reproject layers on-the-fly so that data in different CRS can be shown together, but it's good practice to set your project CRS to match the CRS you want to work in.

Examine the CRS of a Data Layer

  1. Right-click on the Study_Area layer and select Properties.

  2. Click on the Source tab and note the Coordinate Reference System listed:

    EPSG:32630 — WGS 84 / UTM zone 30N

    What is UTM? Universal Transverse Mercator (UTM) is a projected coordinate system that divides the world into 60 zones. Each zone uses meters as its unit, which makes it ideal for measuring distances and areas. London falls in UTM Zone 30N. The "WGS 84" part tells you which model of the Earth's shape (datum) is being used.

  3. Click OK to close the Properties dialog.

  4. Now check the Project CRS: go to Main Menu > Project > Properties and click the CRS tab. It should currently show:

    EPSG:3857 — WGS 84 / Pseudo-Mercator

    This is the CRS of the basemap (the first layer added to the project), and it has become the default Project CRS.

Change the Project CRS

For spatial analysis, we want our project in the same projected (meter-based) CRS as our Study Area layer. Let's change it:

  1. In the CRS tab of Project Properties, type 32630 into the Filter box, or find it under "Recently used coordinate reference systems."

  2. Select EPSG:32630 — WGS 84 / UTM zone 30N and click OK.
  3. Save your project by clicking the Save button on the toolbar.

You should see the study area rectangle rotate slightly — it is now oriented true north-south, because UTM Zone 30N aligns its grid to the north in this part of the world.

Adding and Visualizing Data

Create a Point Layer from a CSV Table

As you learned in Week 00, spatial data doesn't always come in a spatial format. A very common scenario is receiving a CSV (comma-separated values) file that has columns for latitude and longitude. QGIS can convert these coordinates into map points.

Key concept: Creating points from a CSV produces a temporary, dynamic layer — it references the original CSV file on disk. If you move or delete the CSV, the layer breaks. To make it permanent, you would export it to a spatial format like GeoJSON or shapefile. (We'll practice exporting later in this lab.)

  1. Click the Data Source Manager button on the toolbar (or go to Layer > Add Layer > Add Delimited Text Layer).
  2. Click the Delimited Text tab and configure the settings as follows:
  3. For File Name, browse to the data folder and select deathAddresses.csv.
Setting Value
File Format CSV
Record and Field Options "First record has field names" = checked; "Detect field types" = checked
Geometry Definition Point coordinates:X field = xcoord, Y field = ycoord
Geometry CRS EPSG:4326 - WGS 84

  1. Click Add & Close to import the layer.

You should now see a cluster of points in the Soho area — these are the addresses where cholera deaths occurred.

Why EPSG:4326? The coordinates in this CSV are in latitude and longitude (decimal degrees), which is the WGS 84 geographic coordinate system (EPSG:4326). It is necessary to tell QGIS what the coordinates ACTUALLY ARE, not what we WANT them to be, in this step. Even though our project is now in UTM (EPSG:32630), QGIS reprojects the points on-the-fly so everything lines up.

Layer Symbology — Proportional Symbols

Symbology is how you control the visual appearance of your data on the map. You've already applied a symbology to the Study Area polygon layer, so now let's get a little more complex.

Right now, all the death address points look the same, but the data includes a Num_Cases field — the number of deaths at each address. Let's make the symbol size reflect this value.

  1. Click on the deathAddresses layer in the Layers panel to ensure it's selected in the Layer Styling panel.
  2. Apply the following symbology settings:
Setting Value
Symbology Type Graduated
Value Num_Cases
Symbol click to change the color if you like
Legend Precision 1
Method Size
Size from 10, 50, 'Map Units'
Classes > Mode Equal Interval
Classes 3

Because QGIS updates symbology live, you should see the changes apply as you adjust each setting.

What is "Graduated" symbology? Unlike Single Symbol (all features look the same) or Categorized (one symbol per unique value), Graduated symbology maps a continuous numeric field to a visual variable like size or color. This is also called a proportional symbol map — a core technique in cartography.

Bonus: Adding Drop Shadows

  1. At the bottom of the Layer Styling panel, check the Draw Effects option, then click the star icon that becomes active.

  2. Enable Drop Shadow and experiment with the settings.
  3. Save your project.

Viewing the Attribute Table

Every vector layer has an attribute table — a spreadsheet-like table where each row is a geographic feature and each column is an attribute (a piece of information about that feature). This is the non-spatial side of your spatial data.

  1. Right-click on the deathAddresses layer in the Layers panel and select Open Attribute Table.

  2. Explore the table: you can sort columns by clicking on their headers, scroll through records, and select features by clicking on row numbers. Notice how selected rows highlight the corresponding points on the map.
  3. Close the Attribute Table when you're done.

Analysis Tools in QGIS

Many of the actual "workhorse" tools in QGIS are accessed through tool dialogs like the ones you are about to use. These dialog windows are where you tell QGIS what data to work on, which fields or parameters to use, and what to call the output.

This is an important pattern to recognize early:

  • You choose one or more input layers.
  • You set any needed parameters or analysis options.
  • You decide whether the output should be temporary or saved as a new file.
  • You click Run and then inspect the result.

Some QGIS tool dialogs include helpful short explanations of what the tool does and what each option means. Sometimes the help text is excellent; sometimes it is minimal or missing. When a tool is unclear, that is normal. It is often useful to search the web, look at the official QGIS documentation, or read forum discussions to better understand what a tool expects and what kind of output it will produce.

Statistics on a Field

The Num_Cases field records the number of cholera deaths at each address. Let's get a quick statistical summary to understand the distribution of deaths, by household, and give ourselves an example of a typical processing tool workflow.

  1. Go to Vector > Analysis Tools > Basic Statistics for Fields.
  2. Set Input layer to deathAddresses and Field to calculate statistics on to Num_Cases.

  3. You can use the convenient [Create temporary layer] option, for the outputs, which creates reports/layers/outputs that disappear if you don't make them permanent before closing the Project Document.

  4. Click Run, then Close.

  5. Look for the Results Viewer panel (it should appear automatically) and click the hyperlink to open the summary report.

What do these statistics tell you? The mean, max, and standard deviation give you a sense of whether deaths were evenly spread across addresses or concentrated at a few locations. This kind of exploratory summary is often the first step in any spatial analysis.

Adding the Water Pump Locations

Now let's add the water pump data. Snow's original map marked 13 public water pumps in the Soho neighborhood. These locations have been captured for you in a GeoJSON file.

Add the Water Pumps Layer

  1. In the Browser panel, navigate to your project's data folder and double-click on Water_Pumps.geojson to add it to your project.
  2. You should see 13 pump points appear on the map, scattered across the Soho neighborhood.

Change the Water Pump Symbology

Before labeling the pumps, change their symbol so they stand out clearly against both the basemap and the historic Snow map.

  1. Select the Water_Pumps layer in the Layers panel.
  2. In the Layer Styling panel, make sure you are on the Symbology tab.
  3. Leave the symbol type as Single Symbol.
  4. Click the symbol preview to edit the marker.
  5. Change the marker color to blue.
  6. Change the marker size to 25 Map Units.
  7. Apply Drop Shadow effect, as before.
  8. Click Apply if needed, and save your project.

This will make the pumps much easier to see as important reference points in the rest of the lab.

Add Labels to the Water Pumps

  1. Select the Water_Pumps layer in the Layers panel.
  2. In the Layer Styling panel, click the Labels tab .
  3. Change the dropdown from No Labels to Single Labels.
  4. Set Value to the Name field.
  5. Increase Text Size to 14.

  6. Click the Buffer

    tab and enable Draw text buffer to add a halo around the text for readability.

Add the Georeferenced Snow Map

The data folder also includes a georeferenced version of John Snow's original cholera map. Let's add it as a visual reference layer.

What is a georeferenced image? A georeferenced image is a picture (like a scanned map or satellite photo) that has been assigned real-world coordinates so QGIS knows where on Earth it belongs. Without georeferencing, a map image is just a picture with no spatial information. We'll cover the georeferencing process itself in a later lab — for now, we're using a map that has already been georeferenced for you.

  1. In the Browser panel, double-click on John_Snow_Map.tif to add it to your project.
  2. The georeferenced map should appear overlaid on your basemap, aligned with the study area. If it's covering your other layers, drag it below the deathAddresses and Water_Pumps layers in the Layers panel.

Important note about drawing order: The order in which layers are displayed in the map is controlled by the order of the layer list in the Layers panel. Layers at the top of the list draw on top of layers below them. The default order in which data is added is not always the best order for visibility, so one of the first things you often need to do in QGIS is reorder layers so the most important information is not hidden.

  1. Use the navigation tools to zoom in and explore — you should be able to see street names, building outlines, and the pump locations marked on Snow's original map lining up with the GeoJSON points.

Tip: You can adjust the transparency of the Snow map layer to see both the historic map and the modern basemap at the same time. In the Layer Styling panel, look for the Opacity slider.

Exploring Spatial Patterns

Now that we have the death addresses and water pump locations on our map, let's use a simple spatial analysis tool to quantify where the center of the outbreak is. The mean center helps you see whether the deaths are clustered near a particular pump.

Spatial Mean (Mean Center)

The mean center (or spatial mean) is simply the average x-coordinate and average y-coordinate of all features — the geographic "center of gravity" of the distribution.

  1. Go to Vector > Analysis > Mean Coordinate(s).
  2. Set Input layer to deathAddresses.
  3. Leave Weight field and Unique ID field blank (optional).

  4. Save the output as Deaths_Spatial_Mean.shp (change the Save As type dropdown) in your data folder.

  5. Click Run, then Close.
  6. Style the resulting point with a distinctive symbol so it stands out.

Weighted Spatial Mean

A simple mean center treats every address equally, but addresses with more deaths should "pull" the center more strongly. A weighted spatial mean accounts for this.

  1. Run the Mean Coordinate(s) tool again.
  2. This time, set Weight field to Num_Cases.

  1. Save the output as Deaths_Weighted_Spatial_Mean.shp.
  2. Style the result with a different symbol.

Notice how the weighted mean center shifts toward the Broad Street pump — addresses with more deaths pull the center in that direction.

Making a Map layout

Now that your data and analysis layers are in place, the last step is to turn your project into a simple map layout for export. A layout is the printable page version of your map. It lets you combine the map itself with cartographic elements like a title, legend, scale bar, credits, and your name.

Important idea: The map canvas is where you explore and edit your data. The Layout Manager is where you compose a finished page for presentation or submission.

Create a New Layout

  1. Save your project.
  2. Go to Project > New Print Layout.

  3. Give the layout a name such as John_Snow_Layout.

  4. Click OK.

You should now see a blank page in the Layout window

Add a Map Frame

The Map Frame is the actual map on the page. It displays whatever area is currently visible in your main QGIS map canvas.

  1. In the Layout window, click Add Item > Add Map or use the Add Map

    tool

  2. Click and drag a rectangle on the page to create the map frame.

  3. If needed, click the map frame to select it, then in the Item Properties panel click Set to map canvas extent so the layout matches the area you were viewing in the main QGIS window.

If the map frame does not look right at first, do not worry. This is normal. You can go back to the main QGIS window, change the zoom or pan position, and then use Set to map canvas extent again.

Clean Up the Map Before Adding Layout Elements

Before you start adding titles, legends, and other layout elements, return to the main QGIS window and make one more decision about what should actually be visible in the final map.

  1. In the Layers panel, turn off the visibility of the Study_Area polygon.
  2. If you want a cleaner, simpler final map, you can also turn off the visibility of the historic John_Snow_Map raster layer.
  3. Return to the Layout window.
  4. Select the map frame and use Set to map canvas extent or the layout refreshcontrols so the map frame updates to match the current map view.

Window-switching tip: On a Mac, you can usually switch between open QGIS windows with Command + `. On Windows, use Alt + Tab to move between open windows, or use the Window menu inside QGIS if needed.

Doing this now will save you time later. It is much better to decide what belongs in the map before you spend time cleaning up the legend, because layers that are turned off or removed may not need legend entries at all.

Add a Title

  1. Click Add Item > Add Label or use the Add Labeltool.
  2. Click near the top of the page and drag a text box.
  3. Enter a title such as John Snow Cholera Outbreak, Soho, 1854.

  4. In Item Properties, click on the Appearance > Font tool

    to increase the font size and adjust the styling so the title stands out clearly.

Add a Legend

  1. Click Add Item > Add Legend, or use the Legend tool.
  2. Click on the page to place the legend.
  3. In the Item Properties panel, review the legend entries.
  4. Uncheck the Auto update feature
  5. Check the Only show items inside linked maps option and note that some of teh legend items disappear from the Legend Items panel, as well as your Legend in the Layout

You will probably notice that some layer names come into the legend exactly as they appear in the Layers panel, including underscores or file-like naming. This is very common, and part of making a clean map is fixing that.

Clean Up the Legend

  1. Click on the legend in the Layout window so its Item Properties appear.
  2. In the Legend Items panel, edit the labels so they read cleanly.

  3. Double-click each item you want to rename.

    • For example, double-click Water_Pumps and change it to Water Pumps.

    • You can also change something like Deaths_Weighted_Spatial_Mean to Deaths: Weighted Spatial Mean.

  4. Remove items that do not help the reader understand the map.

    • For example, Positron usually does not need to appear in the legend, and it often does not have a useful legend patch because it is the basemap.
  5. Use the minus icon in the Legend Items panel to select and remove unneeded legend entries.

Cartographic tip: File names are for computers. Legend labels are for people.

Add a Scale Bar

  1. Click Add Item > Add Scale Bar or use the Scale Bartool.

  2. Click on the page to place it below or in an unused area of the map.

  3. In Item Properties, make sure it is linked to your map frame.

  4. Choose a style that is simple and easy to read.

  5. Experiment with the Scalebar Styling options to find one you like. If you make everything horrible, you can always just delete the current Scalebar, and place a new one!

Add the CRS

Including the Coordinate Reference System helps document how your map is referenced.

  1. Using the same method you use to place your Map Title, place a small text box near the bottom of the page.

  2. Type the CRS information for your project, for example:

    CRS: EPSG:32630 - WGS 84 / UTM zone 30N

  3. Explore the options for Appearance, especially the very useful alignment tools.

Add Your Name and the Date

  1. Again, use the Add Labe tools to place a text box.
  2. Add your name.
  3. Add the date on the same label or in a second label nearby.

These details are important because they identify the map as your work and document when it was produced.

Bonus: Add the Statistical Summary

If you want to add a bit more analytical context to your map, you can include a short text summary of the statistics you calculated earlier for the Num_Cases field.

  1. Return to the main QGIS window.

  2. If needed, open the Results Viewer panel and click the hyperlink to the statistics summary report.

  3. Copy a few useful values from the report, such as the mean, maximum, or standard deviation.
  4. Return to the Layout window.
  5. Use the Add Label tool to draw a text box in an open area of the layout.

  6. Paste or type a short summary, for example:

    Deaths per address summary: mean = ..., max = ..., standard deviation = ...

  7. Resize and position the text box so it supports the layout without covering important content.

This is optional, but it is a nice way to connect the analysis step to the final map you are turning in.

Review and Adjust the Layout

Before exporting, take a minute to clean things up:

  • Make sure the map frame is large enough to be readable.
  • Make sure labels are not covering important map content.
  • Make sure the legend is readable and uses clean names.
  • Make sure the scale bar is connected to the map.
  • Make sure the title, CRS, name, and date are all present.
  • The Move Item Content tool is useful for nudging the map content within the Map Frame.

Export the Layout

  1. In the Layout window, go to Layout > Export as PDF.
  2. Save the file with a clear name such as sunetid_week00_john_snow_map.pdf.
  3. Dismiss the warning about WMS services, if it pops up.
  4. Use the default Export Options, but explore the other options, for later.
  5. Open the PDF to check the Export.
  6. Keep the exported PDF in your project folder so it stays with the rest of your work.

This exported Map PDF is the map you will submit for the Week 00 assignment.

Conclusion

In this lab, you retraced the spatial investigation that helped establish germ theory and modern epidemiology. You:

  • Created a QGIS project and learned to navigate the QGIS interface
  • Added basemap, vector, raster, and CSV-based layers
  • Learned about coordinate reference systems and why projections matter
  • Turned a CSV table into map points using coordinates
  • Used the spatial mean and weighted spatial mean to see where the outbreak was centered

The weighted spatial mean shifts toward the Broad Street pump — the same conclusion Snow and Whitehead reached in 1854, using pen, paper, and shoe leather.

In future labs, we'll build on these skills with georeferencing, digitizing, spatial joins, Voronoi analysis, hotspot mapping, and more.

Further reading on QGIS cartography and map layouts:

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