aburka
 lvl.1
United States
Offline
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I am receiving GPS data from an M210v2 drone using the OSDK 4.0.1, and I have several questions about the GPSDetail struct (https://developer.dji.com/onboard-api-reference/structDJI_1_1OSDK_1_1Telemetry_1_1GPSDetail.html):
typedef struct GPSDetail
{
float32_t hdop; /*!< horizontal dilution of precision */
float32_t pdop; /*!< position dilution of precision */
float32_t fix; /*!< the state of GPS fix */
float32_t gnssStatus; /*!< vertical position accuracy (mm) */
float32_t hacc; /*!< horizontal position accuracy (mm) */
float32_t sacc; /*!< the speed accuracy (cm/s) */
uint32_t usedGPS; /*!< the number of GPS satellites used for pos fix */
uint32_t usedGLN; /*!< the number of GLONASS satellites used for pos fix */
uint16_t NSV; /*!< the total number of satellites used for pos fix */
uint16_t GPScounter; /*!< the accumulated times of sending GPS data */
} GPSDetail; // pack(1)
1. The only information that I could find on the values of the "fix" field is this 2 year old post (https://djisdksupport.zendesk.com/hc/en-us/articles/360023651393-What-is-the-Parameter-Range-and-Meaning-of-GPSDetail-fix-?mobile_site=false):
0x00:no fix
0x01:dead reckoning only
0x02:2D-fix
0x03:3D-fix
0x04:GPS+dead reckoning combined
0x05:Time only fix
Is this still accurate? If so, what does a "time only fix" mean, and can I use the latitude/longitude estimates in that case?
2. Precisely what kind of accuracy measures are given in gnssStatus, hacc and sacc? Are these RMS, 2DRMS, CEP, R95, SEP, or some other statistic? (ref: https://www.gpsworld.com/gps-accuracy-lies-damn-lies-and-statistics/)
3. What are the units of HDOP and PDOP?
4. Is NSV always the sum of usedGPS and usedGLN?
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