GPSEPHEM

Decoded GPS L1 C/A ephemerides

Platform:

OEM719, OEM729, OEM7500, OEM7600, OEM7700, OEM7720, PwrPak7, CPT7, CPT7700, SMART7, SMART2

This log contains a single set of GPS ephemeris parameters.

Message ID: 7

Log Type: Asynch

Recommended Input:

log gpsephema onall

ASCII Example:

#GPSEPHEMA,USB1,30,52.5,SATTIME,2209,496800.000,02000020,1214,16809;
1,496800.0,0,33,33,2209,2209,504000.0,2.656034748e+07,3.711940331e-09,
2.013999822e+00,1.1881368468e-02,9.0331062162e-01,-2.292916179e-06,
1.384504139e-05,1.27000000e+02,-4.17500000e+01,-2.440065145e-07,
-1.601874828e-07,9.8797254649e-01,1.546492989e-10,2.868107379e+00,
-7.51745599e-09,33,504000.0,5.122274160e-09,3.63708e-04,-8.29914e-12,
0.00000,TRUE,1.458576941e-04,4.00000000e+00*b892b91a

#GPSEPHEMA,USB1,29,52.5,SATTIME,2209,506310.000,02000020,1214,16809;
2,506310.0,0,59,59,2209,2209,511200.0,2.656030527e+07,4.114457098e-09,
-3.065876369e+00,2.0427562180e-02,-1.419168291e+00,-3.142282367e-06,
1.297891140e-05,1.24593750e+02,-6.54062500e+01,3.781169653e-07,1.844018698e-07,
9.6608612461e-01,9.000374902e-11,2.777002903e+00,-7.50781273e-09,59,511200.0,
-1.769512892e-08,-6.53255e-04,1.13687e-13,0.00000,TRUE,1.458584443e-04,
4.00000000e+00*613e9e7e

...

#GPSEPHEMA,USB1,1,52.5,SATTIME,2209,506310.000,02000020,1214,16809;
31,506310.0,0,73,73,2209,2209,511200.0,2.656107835e+07,4.222318734e-09,
1.928386048e+00,1.0431749630e-02,3.8970372621e-01,2.447515726e-06,
1.280941069e-05,1.34125000e+02,4.61250000e+01,-1.508742571e-07,2.980232239e-08,
9.5538846447e-01,-2.110802209e-10,-2.6326210009e-01,-7.85925594e-09,
73,511200.0,-1.350417733e-08,-1.77489e-04,-1.59162e-12,0.00000,TRUE,
1.458521844e-04,4.00000000e+00*085ac00a

#GPSEPHEMA,USB1,0,52.5,SATTIME,2209,497010.000,02000020,1214,16809;
32,497010.0,0,49,49,2209,2209,504000.0,2.655950009e+07,4.804485840e-09,
-1.401126814e+00,5.9581462992e-03,-2.285950321e+00,-2.717599273e-06,
6.832182407e-06,2.48281250e+02,-5.08437500e+01,1.899898052e-07,1.490116119e-08,
9.5774991123e-01,-5.596661695e-10,-1.341873629e+00,-8.19927010e-09,49,504000.0,
4.656612873e-10,-1.26368e-04,-8.64020e-12,0.00000,TRUE,1.458657670e-04,
4.00000000e+00*82ba7dc8

The GPSEPHEM log can be used to monitor changes in the orbits of GPS satellites.

To obtain copies of IS-GPS-200, refer to the GPS website (https://www.gps.gov/technical/icwg/).

Field	Field type	Description	Format	Binary Bytes	Binary Offset
1	Log header	GPSEPHEM header For information about log headers, see ASCII, Abbreviated ASCII or Binary.		H	0
2	PRN	Satellite PRN number	Ulong	4	H
3	tow	Time stamp of subframe 1 (s)	Double	8	H+4
4	health	Health status bits 0-5: 6-bit health code as defined in IS-GPS-200, bit 6: Alert flag	Ulong	4	H+12
5	IODE1	Issue of ephemeris data 1	Ulong	4	H+16
6	IODE2	Issue of ephemeris data 2	Ulong	4	H+20
7	week	toe week number computed from Z count week (GPS reference week number)	Ulong	4	H+24
8	z week	Z count week number. This is the week number from subframe 1 of the ephemeris. The ‘toe week’ (field #7) is derived from this to account for rollover	Ulong	4	H+28
9	toe	Reference time for ephemeris (s)	Double	8	H+32
10	A	Semi-major axis (m)	Double	8	H+40
11	ΔN	Mean motion difference (radians/s)	Double	8	H+48
12	M₀	Mean anomaly of reference time (radians)	Double	8	H+56
13	ecc	Eccentricity, dimensionless	Double	8	H+64
14	ω	Argument of perigee (radians)	Double	8	H+72
15	cuc	Amplitude of cosine harmonic correction term to the argument of latitude (radians)	Double	8	H+80
16	cus	Amplitude of sine harmonic correction term to the argument of latitude (radians)	Double	8	H+88
17	crc	Amplitude of cosine harmonic correction term to the orbit radius (m)	Double	8	H+96
18	crs	Amplitude of sine harmonic correction term to the orbit radius (m)	Double	8	H+104
19	cic	Amplitude of cosine harmonic correction term to the angle of inclination (radians)	Double	8	H+112
20	cis	Amplitude of sine harmonic correction term to the angle of inclination (radians)	Double	8	H+120
21	I₀	Inclination angle at reference time (radians)	Double	8	H+128
22	I⁰	Rate of inclination angle (radians/s)	Double	8	H+136
23	Ω_o	Longitude of ascending node of orbit plane (radians)	Double	8	H+144
24	ώ	Rate of right ascension (radians/s)	Double	8	H+152
25	iodc	Issue of data clock	Ulong	4	H+160
26	toc	SV clock correction term (s)	Double	8	H+164
27	tgd	Estimated group delay difference (s)	Double	8	H+172
28	a_f0	Clock aging parameter (s)	Double	8	H+180
29	a_f1	Clock aging parameter (s/s)	Double	8	H+188
30	a_f2	Clock aging parameter (s/s/s)	Double	8	H+196
31	AS	Anti-spoofing on: 0 = FALSE 1 = TRUE	Bool	4	H+204
32	N	Corrected mean motion (radians/s) This field is computed by the receiver.	Double	8	H+208
33	URA	User Range Accuracy variance (m)² The ICD specifies that the URA index transmitted in the ephemerides can be converted to a nominal standard deviation value using an algorithm listed there. We publish the square of the nominal value (variance). The correspondence between the original URA index and the value output is shown in Table: URA Variance	Double	8	H+216
34	xxxx	32-bit CRC (ASCII and Binary only)	Ulong	4	H+224
35	[CR][LF]	Sentence terminator (ASCII only)	-	-	-

URA Variance
Index Value (m)	A: Standard Deviations (m)	Variance: A² (m²)
0	2.0	4
1	2.8	7.84
2	4.0	16
3	5.7	32.49
4	8	64
5	11.3	127.69
6	16.0	256
7	32.0	1024
8	64.0	4096
9	128.0	16384
10	256.0	65536
11	512.0	262144
12	1024.0	1048576
13	2048.0	4194304
14	4096.0	16777216
15	8192.0	67108864