Interrogator Tool

The Interrogator tool answers demographic and dataset questions about whatever is currently selected on your map - for example, "how many people live near these stations?" or "how many jobs fall within this drawn area?" - without needing to run an isochrone or simulation first.

Reach for the Interrogator when you already know the area or entities you want to ask a question about, and just want a quick number. Select one or more entities on the map - stations, drawn polygons, or dataset features - then switch to the Interrogator tool to see live results in a legend at the bottom-right of your map.

If instead you want to explore accessibility from a point over a range of travel times, use the Isochrone tool - it uses the same query system as the Interrogator, but calculates catchment based on travel time rather than your current selection.

Note: Before the Interrogator can show any results, you need: at least one dataset imported and visible on the map, at least one query set up in the tool panel, and one or more entities selected.

1. Import and make visible the dataset you want to query (for example, population or employment data).
2. Using the Select tool, select the entities you want to ask a question about. This could be one or more stations, a drawn polygon, or entities from another dataset.
3. Switch to the Interrogator tool. The current selection is kept, so your queries run immediately.
4. Click Add to create a query, or use an existing one if you've already set one up.
5. Results appear as a legend in the bottom-right of the map, listing each query's name and its calculated value.

How your selection is interrogated

What counts as the "area" being queried depends on what you've selected:

• Selecting a point entity (such as a station) automatically creates an 800m buffer around it, and the query is run against that catchment.
• Selecting a polygon (such as a drawn shape, or a polygon dataset entity) runs the query against that exact shape.
• Selecting multiple entities combines all of their resulting areas, so a query can cover several stations or shapes at once.

Results update automatically whenever you change your selection, so you can compare different stations, routes, or areas just by reselecting them.

The Interrogator uses the same query editor as isochrone queries, so if you've built dataset queries there before, the settings will be familiar:

• Name - the label shown for this query in the results legend.
• Weight - what's being measured: a fixed value per entity (Total Per Entity), a percentage of a numeric attribute (From Attribute), or a simple entity count (Count Entities).
• Aggregation - how matching values are combined: Sum, Average, Minimum, or Maximum.
• Display As Percentage of Total - available for Sum, this shows the result as a percentage of the value across all matching entities in the dataset, rather than an absolute figure.
• Precision - the number of decimal places shown in the result.
• Accuracy - the sampling grid size used for polygon-based dataset entities; leave this on auto unless you need finer control over precision versus performance.
• Filter Dataset Entities - an optional query to restrict which entities are considered, for example only entities of a certain type or above a certain value.

See the full breakdown of these settings, including how to build filters, in the isochrone queries article.

Use the Settings button on an existing query to edit it, Duplicate to create a variant, or Delete to remove it.

Tip: If you regularly ask the same questions of a dataset across projects, consider setting up default queries for that dataset so they're available automatically wherever it's referenced.

• The Interrogator only considers dataset entities that are currently visible on the map, so if a query result looks wrong, check that the relevant layer isn't hidden.
• Results are recalculated automatically as your selection or the underlying dataset changes, so there's no separate "run" step.
• If you don't see the Interrogator tool on your toolbar, contact your Podaris representative or support to have it enabled for your project.