Routing API Developer's Guide

Setting the level of detail

The isoline polygon can contain a lot of points which may be a problem for visualizing it on higher zoom levels.

Below is an example of the 10km isoline calculated in the center of Berlin.

https://isoline.route.cit.api.here.com/routing/7.2/calculateisoline.json
?app_id={YOUR_APP_ID}
&app_code={YOUR_APP_CODE}
&mode=shortest;car;traffic:disabled
&rangetype=distance
&start=geo!52.51461,13.37827
&range=10000
Figure 1. Example of isoline with many points.

There are two ways to control the level of detail of the isoline polygon. The first one is view resolution. The view resolution allows the client to specify the level of detail needed for visualizing the polygon. It is specified in meters per pixel and reflects the client's zoom level and screen resolution. The isoline service will use this value in order to find the optimal level of detail.

Below is an example of the same isoline request, with view resolution parameter:

https://isoline.route.cit.api.here.com/routing/7.2/calculateisoline.json
?app_id={YOUR_APP_ID}
&app_code={YOUR_APP_CODE}
&mode=shortest;car;traffic:disabled
&rangetype=distance
&start=geo!52.51461,13.37827
&range=10000
&resolution=50
Figure 2. Example of isoline with view resolution applied.

The second way is to set the maximum number of points allowed in the isoline. Once a number is provided in the request the service will automatically adjust the level of detail and perform shape simplification in order to fit within the limit.

Note: This option should be used if client has some physical limitation on the amount of points it is able to process. Please avoid using this option to control zoom level, use view resolution instead. View resolution and max points can be used at the same time.

Below is an example of the same isoline request, with max points parameter:

https://isoline.route.cit.api.here.com/routing/7.2/calculateisoline.json
?app_id={YOUR_APP_ID}
&app_code={YOUR_APP_CODE}
&mode=shortest;car;traffic:disabled
&rangetype=distance
&start=geo!52.51461,13.37827
&range=10000
&maxpoints=50
Figure 3. Example of isoline with max points applied.