Isochrone Queries

Podaris allows you to perform advanced geospatial analysis on the areas serviced by your networks by generating queries related to your data layers.

Street based isochrones

Isochrone queries can help you understand how travel-time and catchment in your networks relate to the distribution of entities within a dataset. This feature can help you answer questions such as:

  • How many people live within 10 mins of stops along a bus route?
  • How many more low-income units does Scenario A provide connectivity to compared to Scenario B?
  • If I move our office to location X, how many employees can reach it in 15 mins? 30 mins? 45 mins?

In this tutorial, we will use the isochrone query tool to explore this in relation to rental developments in the Santa Clara area.

Exploring reach and travel time from a specific point

  1. Having constructed your transport network, import the dataset you wish to query, as per the instructions on datasets.
  2. Click isochrone to open the isochrone panel.
  3. If you have selected travel time you will be able to explore accessibility either from or to a specific point on your map, at a time designated by the respective service day and departure/arrival time.
  4. Click a point on your map to set it as either a start or destination point.
  5. Click add on the QUERIES section of the isochrone tool panel to load the Isochrone Query editor.
  6. Having given our query a name, we're going to take a specific attribute from our dataset - in this case, total_affo, a number representing the amount of affordable units associated with that entity.
    Isochrone Query Editor
  7. Click OKAY and then update to generate a list of affordable units within a range of travel times.

Constructing Queries

In constructing a query, you are required to specify several values:

  • Name:  This will be displayed on the travel time chart.
  • Total per entity/From Attribute: Whether this query applies to each entity in a dataset, or to a specific attribute.
  • Weight: A multiplier of either your total per entity or attribute value.
  • Aggregation: Sum/average/minimum/maximum.

With each amendment to your query, you are required to click update on the isochrone tool panel before you can see your changes.

Filtering Dataset Entries

dataset filtering

With dataset filtering, you can create complex filters using logical operations on the attributes of your data layers. Once you have added more than one rule with the add rule button, you can apply either an and or or boolean operator between them.

Rules can also be nested in groups with the add group button.

All dataset entries visible when filtering are derived from the dataset's attributes with the exception of Layer (which can be used to reference the entire layer by name) and Geometry Type.

You can read more about constructing queries and the available properties usable as filters here.

attribute types

Filtering and Understanding Travel Time by Geometry Type

Below is an example of using the isochrone tool to quickly select all dataset features of a particular type (polygons, representing offices), and perform travel time analysis using them.

Further examples

You can find a range of examples of isochrone analysis that use queries to explore travel time and access time here.