Positions

_|

This page covers position data representation using GemPosition and GemImprovedPosition classes for GPS-based systems.

---

tip

Don't confuse Coordinates with Position classes. The Coordinates class represents geographic locations (latitude, longitude, altitude) and is widely used throughout the SDK. In contrast, GemPosition and GemImprovedPosition classes contain additional sensor data and primarily represent the user's location and movement details.

Create positions

Instantiate the GemPosition class using methods in the SenseDataFactory class. You can also access it through methods exposed by the Maps SDK for Flutter.

For more details, refer to the Get Started with Positioning guide.

---

Raw position data

Raw position data represents unprocessed GPS sensor data from devices. It corresponds to the GemPosition interface.

Map matched position data

Map matching aligns raw GPS data with a digital map, correcting inaccuracies by snapping the position to the nearest logical location (such as roads). It corresponds to the GemImprovedPosition interface.

---

Compare position types

Map matched positions provide more information than raw positions:

Attribute	Raw	Map Matched	When is available	Description
acquisitionTime	✅	✅	always	The system time when the data was collected from sensors.
satelliteTime	✅	✅	always	The satellite timestamp when position was collected by the sensors.
provider	✅	✅	always	The provider type (GPS, network, unknown)
latitude & longitude	✅	✅	hasCoordinates	The latitude and longitude at the position in degrees
altitude	✅	✅	hasAltitude	The altitude at the given position. Might be negative
speed	✅	✅	hasSpeed	The current speed (always non-negative)
speedAccuracy	✅	✅	hasSpeedAccuracy	The current speed accuracy (always non-negative). Typical accuracy is 2 m/s in good conditions
course	✅	✅	hasCourse	The current direction of movement in degrees (0 north, 90 east, 180 south, 270 west)
courseAccuracy	✅	✅	hasCourseAccuracy	The current heading accuracy is degrees (typical accuracy is 25 degrees)
accuracyH	✅	✅	hasHorizontalAccuracy	The horizontal accuracy in meters. Always positive. (typical accuracy 5-20 meters)
accuracyV	✅	✅	hasVerticalAccuracy	The vertical accuracy in meters. Always positive.
fixQuality	✅	✅	always	The accuracy quality (inertial – based on extrapolation, low – inaccurate, high – good accuracy, invalid – unknown)
coordinates	✅	✅	hasCoordinates	The coordinates of the position
roadModifiers	❌	✅	hasRoadLocalization	The road modifiers (such as tunnel, bridge, ramp, etc.)
speedLimit	❌	✅	always	The speed limit on the current road in m/s. It is 0 if no speedLimit information is available
terrainAltitude	❌	✅	hasTerrainData	The terrain altitude in meters. Might be negative. It can be different than altitude
terrainSlope	❌	✅	hasTerrainData	The current terrain slope in degrees. Positive values for ascent, negative values for descent.
address	❌	✅	always	The current address.

info

The speedLimit field may not always have a value, even if the position is map matched. This can happen if data is unavailable for the current road segment or if the position is not on a road. In such cases, the speedLimit field will be set to 0.

tip

To check if a user is exceeding the legal speed limit, use the AlarmService class. Refer to the speed warnings guide for more details.