RTCM1004 and RTCM1077 pseudo-range fields don't match .. ?

[jonathanmuller]

Hi,

First of all thank you a lot for all this amazing project.

I'm trying to use RTCM message from a local basestation to calculate the location of my receiver using DGPS and state of the art algorithm.
I had success using RTCM1004 message, but not RTCM1077, even if their fields should contain the same value, but with different accuracy (if I understand correctly).

Here is my logic, and where is fails :
I'm looking at RTCM1004 and RTCM1077 messages from the same base-station, recorded at the same time, and compare the signal from the same satellites. I expected the pseudorange from both message (for the same satellite) to be the same, within few millimeters. However, There seem to have a problem with the DF405 field, or the way I use it.
Index 1 of RTCM1004 matches index 5 of RTCM1077, both are satellite 15

Type	RTCM1004	RTCM1077	Comment
Timestamp	DF004=379501000	DF004=379501000	Same timestamp
PRN	DF009_01=15	PRN_05=015	Same PRN
Phase modulo	DF014_01=81	DF397_05=81	Same modulo of the phase
Rough range	DF011_01=191957.32	DF398_05=0.640625 0.640625*299792458/1000=192054.54340625	Difference of −97,22...[m]
Accurate range	/	DF405_05=4.433095455169678e-05 4.433095455169678e-05*299792458/1000=13.29...	Why is it not close to −97,22 ?

It looks to me : the time, PRN, etc, all match. But for some reasons DF405 is completely ... random ?
I'm probably using it wrongly, but based on RTCM documentation it looks like the full range was divided into smaller fields : DF397, DF398 and DF405

What am I doing wrong, are RTCM1004 and RTCM1077 not representing the same "kind" of pseudo-range ?

Full code to replicate, with output.

from laika.constants import SPEED_OF_LIGHT

from pyrtcm import RTCMReader

'''

# a = RTCM1004
# b = RTCM1077
a = b'\xd3\x00\xa5>\xc0\x00Zz\xe7"\xa0=$\xe7U\xe8\xb6\xff\xd4j\x00\x03\xfa\xc7K\xfd\x02\xe8\xe8\xb6\x08\x00\x00t\xaa\xb8\x01\xac\x05\x98OY\x19%*-\x01\x03o\xf4\x9b\x83\xfa\x90Wj\xffX\xc3\x14fk\xfc\'\xbf\xa2d\x1f\xc1|^_\xfc\x01\x82k\xad\x81\xa3\x87\xfdJ\x90\x01\xd0\x1cp?\xd0@\'\xd6\xf0\xf6\xbc\xcf\xe9\xf5\x87\xf8?\x85Q\xfe\xa0\xc0p:\xdf\xdd\xf1\x7fD\xc8>\xbe\xf8s\x1f\xf8\x05)g)\xbc\x97\xbb\xfa\x95\x01\xff\xa7o`\xff\x9cM\xa0l\xae\x01F\xdf\xd2\xae\x08\x00 \x00\x03\xf8\x01k\xb6\x95\x9fc\x7f\x82\xab\x00\x04\x93\xfd\x81O\x1e\x00\xb41\x17'
b = b'\xd3\x01\x03CP\x00Zz\xe7"\x00\x00\x029\x11\xc0\x80\x00\x00\x00 \x00@\x00\x7f\xf7\xfa\x92\x92\xaa"\x8aR\xaa"Jx\x00\x00\x00\x00\x00\xafr\xe8\xe1\xfd!\xd2O\xdb\x92\x9aY}\xa0\x0f\xb7\xc9\x1f\xf6\x06\xcc\x0e\xc8W@\xcf\xfc\xbd\xf4\x06\xc9\xf4m \xa1\xca\xd0\x1c\x9f\xb8.|\x05vo:Tr<\xbe\xab\xf3\xea\xd0 \xae\xde\x8b*\xb0\xc1\xa8\x9a\xf0\x91\xa6D\xf1\x95\xaf\x13G\x177\x19o\x0f\x83Q\xf0y\xd0\xc9}\xf5P\x0c||\x80\x96\x8a\x81\xeb\xca\x83\xce\xd3~\xb5]\xfd\x93\x19\x009)\x88{w{L\x9f\x88c\xe1\x80\xa8\x8a~\xd5\xebw\xcc*\x03\xf9w}J,\x86\xd4]@O\xfc\xb1-4L\xe4\xcf3\xd0\x93\xcc\xda\xcb\xb3\xb3\xe4\xf9"H\xf14F\x00\x00)\n\x02\x80\x9c \x07\x83 \xc0*\n\x02\xe0\\\x19\x0c\x83\x00\xb8+\n\xc2\xa0\x14 "\x04f\xb1\x01a\xb5\xc2i@\x11\x00\x88\xec\xf9\xc7\x9c\x80/\xddP!\x80i\xc0\x82\x8a3\x13X6\xd8o\x98\x9b-\xe6'

a_parsed = RTCMReader.parse(a)
b_parsed = RTCMReader.parse(b)

print(a_parsed, end="\n\n")
print(b_parsed, end="\n\n")

a_msg_time_of_week = a_parsed.DF004 / 1000
b_msg_time_of_week = b_parsed.DF004 / 1000

a_sat_num = a_parsed.DF006
print(f"{a_msg_time_of_week=} {b_msg_time_of_week=} -> {a_msg_time_of_week - b_msg_time_of_week}")
for a_idx in range(a_sat_num):
    a_prn = int(getattr(a_parsed, f"DF009_{a_idx + 1:02}"))

    a_phase_mod = getattr(a_parsed, f"DF014_{a_idx + 1:02}")  # integer
    a_phase = getattr(a_parsed, f"DF011_{a_idx + 1:02}")  # float part

    b_idx = None
    for j in range(a_sat_num):
        b_prn = int(getattr(b_parsed, f"PRN_{j + 1:02}"))
        if a_prn != b_prn:
            continue
        b_idx = j
        break
    b_prn = int(getattr(b_parsed, f"PRN_{b_idx + 1:02}"))

    b_phase_mod = float(getattr(b_parsed, f"DF397_{b_idx + 1:02}"))  # integer
    b_phase = getattr(b_parsed, f"DF398_{b_idx + 1:02}") * SPEED_OF_LIGHT / 1000  # float part
    b_phase_plus = float(getattr(b_parsed, f"DF405_{b_idx + 1:02}")) * SPEED_OF_LIGHT / 1000  # float part more accurate
    b_phase += b_phase_plus
    print(f"Comparison A vs B : {a_phase_mod=} VS {b_phase_mod=} ({a_phase_mod - b_phase_mod})// {a_phase} VS {b_phase} ({a_phase - b_phase}) // 0 vs {b_phase_plus=} ")

<RTCM(1004, DF002=1004, DF003=0, DF004=379501000, DF005=1, DF006=10, DF007=0, DF008=0, DF009_01=15, DF010_01=0, DF011_01=191957.32, DF012_01=-23.8445, DF013_01=127, DF014_01=81, DF015_01=42.0, DF016_01=0, DF017_01=0.3, DF018_01=-42.775, DF019_01=127, DF020_01=40.0, DF009_02=23, DF010_02=0, DF011_02=186835.84, DF012_02=-262.144, DF013_02=58, DF014_02=85, DF015_02=23.0, DF016_02=0, DF017_02=4.28, DF018_02=5.729, DF019_02=61, DF020_02=25.0, DF009_03=25, DF010_03=0, DF011_03=97425.16, DF012_03=4.1505, DF013_03=127, DF014_03=73, DF015_03=46.0, DF016_03=0, DF017_03=-1.74, DF018_03=11.189, DF019_03=127, DF020_03=43.0, DF009_04=24, DF010_04=0, DF011_04=258342.92, DF012_04=-1.969, DF013_04=127, DF014_04=68, DF015_04=50.0, DF016_04=0, DF017_04=-2.52, DF018_04=-14.874500000000001, DF019_04=127, DF020_04=48.0, DF009_05=6, DF010_05=0, DF011_05=25382.0, DF012_05=26.8495, DF013_05=127, DF014_05=82, DF015_05=41.0, DF016_05=0, DF017_05=2.32, DF018_05=14.56, DF019_05=127, DF020_05=40.0, DF009_06=32, DF010_06=0, DF011_06=52218.56, DF012_06=-18.97, DF013_06=127, DF014_06=79, DF015_06=43.0, DF016_06=0, DF017_06=-1.26, DF018_06=-7.852, DF019_06=127, DF020_06=42.0, DF009_07=12, DF010_07=0, DF011_07=18387.74, DF012_07=-8.719, DF013_07=127, DF014_07=68, DF015_07=50.0, DF016_07=0, DF017_07=-6.44, DF018_07=-15.4635, DF019_07=127, DF020_07=48.0, DF009_08=10, DF010_08=0, DF011_08=217070.84, DF012_08=-27.913, DF013_08=127, DF014_08=82, DF015_08=40.0, DF016_08=0, DF017_08=-0.24, DF018_08=-37.0235, DF019_08=127, DF020_08=39.0, DF009_09=19, DF010_09=0, DF011_09=272907.98, DF012_09=1.307, DF013_09=127, DF014_09=74, DF015_09=46.0, DF016_09=0, DF017_09=-163.84, DF018_09=-262.144, DF019_09=127, DF020_09=0.0, DF009_10=11, DF010_10=0, DF011_10=245644.02000000002, DF012_10=-20.0325, DF013_10=65, DF014_10=85, DF015_10=32.0, DF016_10=0, DF017_10=11.700000000000001, DF018_10=-2.555, DF019_10=60, DF020_10=30.0)>

<RTCM(1077, DF002=1077, DF003=0, DF004=379501000, DF393=1, DF409=0, DF001_7=0, DF411=0, DF412=0, DF417=0, DF418=0, DF394=320357560454479872, NSat=10, DF395=1073774592, NSig=2, DF396=1048319, NCell=19, PRN_01=006, PRN_02=010, PRN_03=011, PRN_04=012, PRN_05=015, PRN_06=019, PRN_07=023, PRN_08=024, PRN_09=025, PRN_10=032, DF397_01=82, DF397_02=82, DF397_03=85, DF397_04=68, DF397_05=81, DF397_06=74, DF397_07=85, DF397_08=68, DF397_09=73, DF397_10=79, ExtSatInfo_01=0, ExtSatInfo_02=0, ExtSatInfo_03=0, ExtSatInfo_04=0, ExtSatInfo_05=0, ExtSatInfo_06=0, ExtSatInfo_07=0, ExtSatInfo_08=0, ExtSatInfo_09=0, ExtSatInfo_10=0, DF398_01=0.0849609375, DF398_02=0.7236328125, DF398_03=0.8193359375, DF398_04=0.0615234375, DF398_05=0.640625, DF398_06=0.91015625, DF398_07=0.623046875, DF398_08=0.861328125, DF398_09=0.3251953125, DF398_10=0.173828125, DF399_01=-304, DF399_02=502, DF399_03=-440, DF399_04=-20, DF399_05=870, DF399_06=473, DF399_07=698, DF399_08=415, DF399_09=-418, DF399_10=-384, CELLPRN_01=006, CELLSIG_01=1C, CELLPRN_02=006, CELLSIG_02=2X, CELLPRN_03=010, CELLSIG_03=1C, CELLPRN_04=010, CELLSIG_04=2X, CELLPRN_05=011, CELLSIG_05=1C, CELLPRN_06=011, CELLSIG_06=2X, CELLPRN_07=012, CELLSIG_07=1C, CELLPRN_08=012, CELLSIG_08=2X, CELLPRN_09=015, CELLSIG_09=1C, CELLPRN_10=015, CELLSIG_10=2X, CELLPRN_11=019, CELLSIG_11=1C, CELLPRN_12=023, CELLSIG_12=1C, CELLPRN_13=023, CELLSIG_13=2X, CELLPRN_14=024, CELLSIG_14=1C, CELLPRN_15=024, CELLSIG_15=2X, CELLPRN_16=025, CELLSIG_16=1C, CELLPRN_17=025, CELLSIG_17=2X, CELLPRN_18=032, CELLSIG_18=1C, CELLPRN_19=032, CELLSIG_19=2X, DF405_01=-0.00029568374156951904, DF405_02=-0.0002879723906517029, DF405_03=0.0004375576972961426, DF405_04=0.0004367660731077194, DF405_05=4.433095455169678e-05, DF405_06=8.33515077829361e-05, DF405_07=-0.0001885145902633667, DF405_08=-0.00021000392735004425, DF405_09=-0.0003242958337068558, DF405_10=-0.0003232881426811218, DF405_11=0.00016676820814609528, DF405_12=0.0001703910529613495, DF405_13=0.00018468685448169708, DF405_14=0.0004110671579837799, DF405_15=0.00040270574390888214, DF405_16=-0.00021996162831783295, DF405_17=-0.00022575631737709045, DF405_18=0.0003542359918355942, DF405_19=0.0003500562161207199, DF406_01=0.00020264089107513428, DF406_02=-0.0003774678334593773, DF406_03=-0.00012461841106414795, DF406_04=0.0007621017284691334, DF406_05=3.589177504181862e-05, DF406_06=0.00011725211516022682, DF406_07=0.00023241620510816574, DF406_08=-7.882947102189064e-05, DF406_09=-0.00014803465455770493, DF406_10=1.3628508895635605e-05, DF406_11=0.0005177175626158714, DF406_12=-0.0002869074232876301, DF406_13=0.0005120947025716305, DF406_14=4.0182843804359436e-05, DF406_15=-7.106829434633255e-05, DF406_16=-0.0005006399005651474, DF406_17=0.0002425825223326683, DF406_18=-0.00016542105004191399, DF406_19=0.0004168422892689705, DF407_01=514, DF407_02=511, DF407_03=600, DF407_04=602, DF407_05=418, DF407_06=412, DF407_07=615, DF407_08=615, DF407_09=644, DF407_10=633, DF407_11=621, DF407_12=407, DF407_13=413, DF407_14=636, DF407_15=636, DF407_16=580, DF407_17=583, DF407_18=550, DF407_19=547, DF420_01=0, DF420_02=0, DF420_03=0, DF420_04=0, DF420_05=0, DF420_06=0, DF420_07=0, DF420_08=0, DF420_09=0, DF420_10=0, DF420_11=0, DF420_12=0, DF420_13=0, DF420_14=0, DF420_15=0, DF420_16=0, DF420_17=0, DF420_18=0, DF420_19=0, DF408_01=41.0, DF408_02=40.0, DF408_03=40.0, DF408_04=39.0, DF408_05=32.0, DF408_06=30.0, DF408_07=50.0, DF408_08=48.0, DF408_09=42.0, DF408_10=40.0, DF408_11=46.0, DF408_12=23.0, DF408_13=25.0, DF408_14=50.0, DF408_15=48.0, DF408_16=46.0, DF408_17=43.0, DF408_18=43.0, DF408_19=42.0, DF404_01=0.2576, DF404_02=0.2177, DF404_03=0.3286, DF404_04=0.4118, DF404_05=0.3502, DF404_06=0.2469, DF404_07=0.0034000000000000002, DF404_08=0.013600000000000001, DF404_09=-0.2436, DF404_10=-0.3609, DF404_11=0.4101, DF404_12=-0.0555, DF404_13=0.0268, DF404_14=0.042300000000000004, DF404_15=0.0261, DF404_16=0.2611, DF404_17=0.24760000000000001, DF404_18=0.35100000000000003, DF404_19=0.35710000000000003)>

a_msg_time_of_week=379501.0 b_msg_time_of_week=379501.0 -> 0.0
Comparison A vs B : a_phase_mod=81 VS b_phase_mod=81.0 (0.0)// 191957.32 VS 192067.83349208056 (-110.51349208055763) // 0 vs b_phase_plus=13.290085830539464 
Comparison A vs B : a_phase_mod=85 VS b_phase_mod=85.0 (0.0)// 186835.84 VS 186728.23885308483 (107.60114691517083) // 0 vs b_phase_plus=-56.51525238391757 
Comparison A vs B : a_phase_mod=73 VS b_phase_mod=73.0 (0.0)// 97425.16 VS 97393.88061934698 (31.27938065302442) // 0 vs b_phase_plus=-97.22144510613754 
Comparison A vs B : a_phase_mod=68 VS b_phase_mod=68.0 (0.0)// 258342.92 VS 258156.71814471134 (186.20185528867296) // 0 vs b_phase_plus=-62.95759356992319 
Comparison A vs B : a_phase_mod=82 VS b_phase_mod=82.0 (0.0)// 25382.0 VS 25382.004531433613 (-0.004531433613010449) // 0 vs b_phase_plus=-88.64375567576289 
Comparison A vs B : a_phase_mod=79 VS b_phase_mod=79.0 (0.0)// 52218.56 VS 52015.44151634462 (203.11848365538026) // 0 vs b_phase_plus=-96.91934693662822 
Comparison A vs B : a_phase_mod=68 VS b_phase_mod=68.0 (0.0)// 18387.74 VS 18575.201727362346 (-187.4617273623444) // 0 vs b_phase_plus=130.9391746279709 
Comparison A vs B : a_phase_mod=82 VS b_phase_mod=82.0 (0.0)// 217070.84 VS 216853.32759799852 (217.5124020014773) // 0 vs b_phase_plus=-86.33195082961024 
Comparison A vs B : a_phase_mod=74 VS b_phase_mod=74.0 (0.0)// 272907.98 VS 272882.96750495874 (25.0124950412428) // 0 vs b_phase_plus=24.988153396252542 
Comparison A vs B : a_phase_mod=85 VS b_phase_mod=85.0 (0.0)// 245644.02000000002 VS 245761.9111284486 (-117.89112844859483) // 0 vs b_phase_plus=131.17649758923054