Mapping Geographic Data Flashcards

An analyst is attempting to map customer locations using a field named 'Postal Code'. When the field is dragged into the view, Tableau does not automatically generate a map. In the Data pane, the field has an 'Abc' icon next to it. What is the most likely first step the analyst should take to resolve this?

Answer: Right-click the 'Postal Code' field, go to 'Geographic Role', and assign it 'ZIP Code/Postcode'.

Tableau uses geographic roles to interpret and geocode location data. If a field like 'Postal Code' is not automatically recognized (indicated by the 'Abc' or string icon), the user must manually assign the correct geographic role (e.g., 'ZIP Code/Postcode') so Tableau can generate the necessary latitude and longitude coordinates to create a map.

A city planner is creating a single map visualization to analyze public transportation usage. The goal is to show each individual bus stop as a point, overlaid on top of a filled map representing the population density by neighborhood. Which Tableau feature is the most efficient way to combine these two distinct geographic layers on one map?

Answer: Add the bus stop data as a new Marks Layer on top of the neighborhood map.

The Map Layers feature is specifically designed to add multiple layers of geographic information onto a single map, even from different data sources. This is more flexible than the older dual-axis map method, which was limited to two layers. By creating a base map (filled neighborhoods), the planner can simply drag the geographic fields for bus stops onto the map to create a new marks layer.

An energy company needs to map its proprietary pipeline segments, which are identified by custom names like 'Alpha-Line' and 'Beta-Spur'. These are not standard geographic entities that Tableau recognizes. To map these custom locations, the company has a separate file that links each segment name to its correct latitude and longitude. What should the analyst do?

Answer: From the Map menu, select 'Geocoding' and 'Import Custom Geocoding' to load the file with location data.

When Tableau does not recognize geographic data, you can extend its capabilities by importing custom geocoding. This involves creating a file (e.g., a .csv) that maps your custom location names to latitudes and longitudes, and then importing it into Tableau. This creates a new, custom geographic role that can be assigned to your field.

A user has a dataset with thousands of individual customer addresses plotted on a map. Because many customers live close together, the marks overlap significantly, making it difficult to see where the highest concentrations of customers are. Which of the following map types is best suited to clearly visualize these areas of high concentration?

Answer: A density map (heatmap).

A density map, or heatmap, is specifically designed to visualize the concentration of marks in an area, especially when many points overlap. It uses color intensity to represent the number of points, making it easy to identify clusters and hot spots that would be obscured on a standard symbol map.

An analyst has a data source that contains two separate numeric fields: `[Customer_Lat]` for latitude and `[Customer_Lon]` for longitude. To plot these exact locations as points on a map, which Tableau calculation should be used?

Answer: MAKEPOINT([Customer_Lat], [Customer_Lon])

The `MAKEPOINT` function is a spatial function in Tableau that takes latitude and longitude values as inputs and generates a spatial geometry point. The resulting calculated field has a geographic data type and can be placed on a worksheet to create a map.

When mapping sales by city, a user notices a small indicator in the bottom-right corner of the map that says '12 ambiguous'. This occurs because a city name like 'Durham' exists in both the UK and the USA within the dataset. What is the most direct way to resolve this ambiguity within the view?

Answer: Add a higher-level geographic field, such as 'Country' or 'State', to Detail on the Marks card.

Tableau can resolve ambiguous location names when provided with more geographic context. By adding a higher-level geographic dimension (like State, Province, or Country) to the view (typically on the Detail shelf), you give Tableau the necessary information to distinguish between identical lower-level names (e.g., Durham, North Carolina vs. Durham, England).