SDK for iOS performs Map Matching automatically when it needs to match a raw position to the road network, e.g. during drive guidance when there may be inaccuracies in the road rendering or GPS data. Map matching also supports cases when the GPS signal is lost while entering a road tunnel. The position is extrapolated and updated based on the driver’s speed and knowledge of the tunnel layout.
Automotive Map Matching
SDK for iOS supports high-accuracy map matching through the
NMAPositionDataSourceAutomotive class. As a requirement to use this class, you should have positioning data input from a GNSS module that supports dead reckoning. This ensures a continuous and reliable stream of position updates even in cases when GPS becomes unavailable (for example, when the user is driving in a tunnel). It is strongly recommended that position updates are provided at a constant rate of 10 Hz together with standard deviations of the following:
- Horizontal radial error (large component)
- Horizontal radial error (small component)
- Automotive Map Matching is currently offered as a beta feature. APIs may change without notice.
- Automotive Map Matching does not support tunnel extrapolation.
Custom Data Sources
In general, you can also use any custom positioning data by implementing
NMAPositionDataSource class and setting it to
dataSource property in
NMAPositioningManager before starting the positioning manager.