The DUAL Status app sends GPS accuracy data to ForeFlight using the NACp (Navigational Accuracy Category for Position) aviation standard. NACp values are based on Estimated Position Uncertainty (EPU), a measure indicating a 95% chance that the actual position lies within a certain radius around the reported position.
If the DUAL Status app determines that the position information has an NACp value of 9, then ForeFlight will show an accuracy of 30m. The accuracy is somewhere between 10m and 30m.
If the NACp value is calculated as 10, then ForeFlight will show an accuracy of 10m, and the actual accuracy will be between 3m and 10m.
Refer to the table below for a complete list of NACp values and corresponding accuracy levels.
| NACp Value | GPS Accuracy Limits | GPS Accuracy Value Shown in ForeFlight |
| 8 | Value is between 92.6m and 30m | 92.6m |
| 9 | Value is between 10m and 30m | 30m |
| 10 | Value is between 3m and 10m | 10m |
| 11 | Value is less than 3 meters | 3m |
NACp values, accuracy limits, and what is shown within ForeFlight
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