In typical GI systems, reachability tests are usually carried out via Point-In-Polygon tests. Several problems occur due to these tests:
- We need to generate the polygons first
- Depending on the complexity of the polygon, especially for transit polygons and high travel times, this can be a time consuming task
- We need to transfer the generated polygon over the wire (unzipped polygons for large travel times can be >2MB in size) and we have to render them
- The Point-In-Polygon test (PIP) needs to be performed
- This is actually a complex task and can take a lot of time in case of a large number of targets and huge polygons
- Point-In-Polygon tests won’t give you precise travel times for your targets
- Our polygons render at different levels of precision for performance and readability, depending on the zoon level.
To sum this up: Our polygons are great for visualizing travel times. For analyzing them, use our Time service.
- Get precise travel time to all of your source points
- Measure for multiple sources
- Configure travel options to finetune the results
The most powerful part of the Reachability service is that we can get actual measures - not classified distance groups. So we know exactly how far away each point is. In the demo below, we use that precision to determine symbology by applying a d3 color scale to the points, to really visualize precise distance. You can use this for filtering by distance as well..