RAWEPHEM

Raw GPS L1 C/A ephemeris

Platform:

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

This log contains the raw binary information for subframes one, two and three from the GPS satellite L1 C/A signal with the parity information removed. Each subframe is 240 bits long (10 words - 24 bits each) and the log contains a total 720 bits (90 bytes) of information (240 bits x 3 subframes). This information is preceded by the PRN number of the satellite from which it originated. This message is not generated unless all 10 words from all 3 frames have passed parity.

Ephemeris data whose Time of Ephemeris (TOE) is older than six hours is not shown. Multiple logs are output, one for each GPS satellite with collected ephemeris information.

Message ID: 41

Log type: Asynch

Recommended input:

log rawephema onall

ASCII example:

#RAWEPHEMA,USB1,30,54.0,SATTIME,2209,496800.000,02000020,58ba,16809;1,2209,504000,8b0284a1b8a52850000724918b913e21a92dc6ee0b217b0c00ffb72fac04,8b0284a1b92b21fac82899520ec7b7fb31061550921d09a10d62b87b0c7c,8b0284a1b9adff7d74db71f3ffaa2840ed6e0fe024cddf1effadc82106c4*0ea3cca1

#RAWEPHEMA,USB1,29,54.0,SATTIME,2209,512730.000,02000020,58ba,16809;2,2209,518400,8b0284a6e82728500051d2718b913e21a92dc6eeda427e90000001aa606d,8b0284a6e8aa42f8f82d56addef337fa840a758d8d1c42a10d56437e907e,8b0284a6e92f00777124a07100c7275ca76f0e76c62e1e8bffad9c42067f*5581fdb5

#RAWEPHEMA,USB1,28,54.0,SATTIME,2209,496800.000,02000020,58ba,16809;3,2209,504000,8b0284a1b8a52850000724918b913e21a92dc6ee04167b0c00ff88e02542,8b0284a1b92b16057c326224c51f2604ed021ebf6a0db8a10cf92a7b0c7c,8b0284a1b9adffef9ef8203a001627ab6c56208226d033b4ffa63a160f90*73505674

...

#RAWEPHEMA,USB1,2,54.0,SATTIME,2209,489600.000,02000020,58ba,16809;30,2209,496800,8b02849f60a52850000724918b913e21a92dc6ee0847794a00fff3bad3c7,8b02849f612b47046033f40bb132b0041702f88bd31993a10e34eb794a7d,8b02849f61ad0032f5025ef6004b26264dc7108e922777edffa6fe47025e*9763ae6b

#RAWEPHEMA,USB1,1,54.0,SATTIME,2209,512730.000,02000020,58ba,16809;31,2209,518400,8b0284a6e82728500051d2718b913e21a92dc6eee34b7e9000fff2e8bc16,8b0284a6e6294b05352e16795ad6fd044f055757e01ac0a10df3d67e907e,8b0284a6e6afffe1f5457d19ffd026ed0e00105f0fe105f5ffab7a4bf840*7838d9ba

#RAWEPHEMA,USB1,0,54.0,SATTIME,2209,497010.000,02000020,58ba,16809;32,2209,504000,8b0284a1ca242850000724918b913e21a92dc6ee01317b0c00ffb4ef6fcd,8b0284a1c82b31f9a5348cc6e9b79bfa4d030cf2370e54a10cba597b0c7f,8b0284a1c8ad0066c953c01700082705b1a61f09a2dcac5bffa65331e786*f299f05c

A way to use only one receiver and achieve better than 1 metre accuracy is to use precise orbit and clock files. Three types of GPS ephemeris, clock and earth orientation solutions are compiled by an elaborate network of GNSS receivers around the world all monitoring the satellite characteristics. IGS rapid orbit data is processed to produce files that correct the satellite clock and orbit parameters. Since there is extensive processing involved, these files are available on a delayed schedule from the US National Geodetic Survey at: www.ngs.noaa.gov/orbits

Precise ephemeris files are available today to correct GPS data which was collected a few days ago. All you need is one GNSS receiver and a computer to process on. Replace the ephemeris data with the precise ephemeris data and post-process to correct range values.

Field

Field type

Description

Format

Binary bytes

Binary offset

1

Log header

RAWEPHEM header

For information about log headers, see ASCII, Abbreviated ASCII or Binary.

 

H

0

2

PRN

Satellite PRN number

Ulong

4

H

3

ref week

Ephemeris reference week number

Ulong

4

H+4

4

ref secs

Ephemeris reference time (s)

Ulong

4

H+8

5

subframe1

Subframe 1 data

Hex[30]

30

H+12

6

subframe2

Subframe 2 data

Hex[30]

30

H+42

7

subframe3

Subframe 3 data

Hex[30]

30

H+72

8

xxxx

32-bit CRC (ASCII and Binary only)

Hex

4

H+102

9

[CR][LF]

Sentence terminator (ASCII only)

-

-

-