Obtaining Active vehicle data

Hello, I’m trying to present the telemetry data in QGCS in a different way in my custom version. How would I obtain the active vehicle data, for example, the relative altitude? I took a look at the TelemetryValuesBar.qml, but I’m not sure how it accesses the raw data. So far, I have tried things like property real _vehicleAltitude: _activeVehicle ? _activeVehicle.altitudeRelative.rawValue : 0 ,
to obtain the altitude data but its not working.