Clock error, orbit determination accuracy is relatively low

[gnss-freshman]

Dear ginan team： I used sample data to run the pod. Below is my pod.yaml file.

inputs:

include_yamls: [ /home/jddai/ginan/inputData/products/boxwing.yaml ] # required if using boxwing model

inputs_root: /home/jddai/ginan/inputData/products/

atx_files:  [ igs20.atx                             ] # required
egm_files:  [ tables/EGM2008.gfc                    ] # Earth gravity model coefficients file
igrf_files: [ tables/igrf13coeffs.txt               ]
erp_files:  [ finals.data.iau2000.txt        ]
planetary_ephemeris_files: [ tables/DE436.1950.2050 ]

troposphere:
    gpt2grid_files: [ tables/gpt_25.grd ]

tides:
    ocean_tide_loading_blq_files:   [ tables/OLOAD_GO.BLQ                  ] # required if ocean loading is applied
    atmos_tide_loading_blq_files:   [ tables/ALOAD_GO.BLQ                  ] # required if atmospheric tide loading is applied
    ocean_pole_tide_loading_files:  [ tables/opoleloadcoefcmcor.txt ] # required if ocean pole tide loading is applied
    ocean_tide_potential_files:     [ tables/fes2014b_Cnm-Snm.dat   ]

snx_files:
# - "*.SNX" # use a wild card to include all files matching the description in the directory
- tables/igs_satellite_metadata_2203_plus.snx
- tables/sat_yaw_bias_rate.snx
- tables/qzss_yaw_modes.snx
- tables/bds_yaw_modes.snx
- IGS1R03SNX_20191950000_07D_07D_CRD.SNX

satellite_data:
    nav_files: [ brdm1990.19p ]

gnss_observations:
    gnss_observations_root: /home/jddai/ginan/inputData/data
    rnx_inputs:
    - AREG00PER_R_20191990000_01D_30S_MO.rnx
    - ASCG00SHN_R_20191990000_01D_30S_MO.rnx
    - CEDU00AUS_R_20191990000_01D_30S_MO.rnx
    - COCO00AUS_R_20191990000_01D_30S_MO.rnx
    - CPVG00CPV_R_20191990000_01D_30S_MO.rnx
    - DARW00AUS_R_20191990000_01D_30S_MO.rnx
    - DGAR00GBR_R_20191990000_01D_30S_MO.rnx
    - DJIG00DJI_R_20191990000_01D_30S_MO.rnx
    - FAIR00USA_R_20191990000_01D_30S_MO.rnx
    - HERS00GBR_R_20191990000_01D_30S_MO.rnx
    - HOB200AUS_R_20191990000_01D_30S_MO.rnx
    - IISC00IND_R_20191990000_01D_30S_MO.rnx
    - JFNG00CHN_R_20191990000_01D_30S_MO.rnx
    - KARR00AUS_R_20191990000_01D_30S_MO.rnx
    - KIRI00KIR_R_20191990000_01D_30S_MO.rnx
    - KOKV00USA_R_20191990000_01D_30S_MO.rnx
    - LHAZ00CHN_R_20191990000_01D_30S_MO.rnx
    - LMMF00MTQ_R_20191990000_01D_30S_MO.rnx
    - MAW100ATA_R_20191990000_01D_30S_MO.rnx
    - MBAR00UGA_R_20191990000_01D_30S_MO.rnx
    - METG00FIN_R_20191990000_01D_30S_MO.rnx
    - MGUE00ARG_R_20191990000_01D_30S_MO.rnx
    - NICO00CYP_R_20191990000_01D_30S_MO.rnx
    - NKLG00GAB_R_20191990000_01D_30S_MO.rnx
    - OHI300ATA_R_20191990000_01D_30S_MO.rnx
    - POAL00BRA_R_20191990000_01D_30S_MO.rnx
    - QUIN00USA_R_20191990000_01D_30S_MO.rnx
    - REYK00ISL_R_20191990000_01D_30S_MO.rnx
    - RGDG00ARG_R_20191990000_01D_30S_MO.rnx
    - SAMO00WSM_R_20191990000_01D_30S_MO.rnx
    - SEY200SYC_R_20191990000_01D_30S_MO.rnx
    - SOLO00SLB_R_20191990000_01D_30S_MO.rnx
    - TONG00TON_R_20191990000_01D_30S_MO.rnx
    - TOPL00BRA_R_20191990000_01D_30S_MO.rnx
    - TOW200AUS_R_20191990000_01D_30S_MO.rnx
    - USN700USA_R_20191990000_01D_30S_MO.rnx
    - VACS00MUS_R_20191990000_01D_30S_MO.rnx
    - ZIM200CHE_R_20191990000_01D_30S_MO.rnx
    - CUSV00THA_R_20191990000_01D_30S_MO.rnx

outputs:

outputs_root:                   /home/jddai/ginan/out/output_pod_example_300/

metadata:
    config_description:         pod_example
    analysis_agency:            GAA
    analysis_centre:            Geoscience Australia -----FILE NOT FOR OPERATIONAL USE-----
    analysis_software:          Ginan v3.0
    rinex_comment:              AUSNETWORK1
    gradient_mapping_function:  Chen & Herring, 1992        # (string) Name of mapping function used for mapping horizontal troposphere gradients
    ocean_tide_loading_model:   FES2014                     # (string) Ocean tide loading model applied
    reference_system:           igs20                       # (string) Terrestrial Reference System Code
    time_system:                G                           # (string) Time system - e.g. "G", "UTC"

trace:
    level:                      3
    output_receivers:           true
    output_network:             true
    receiver_filename:          <RECEIVER>_<CONFIG>_<YYYY><DDD><HH>.TRACE
    network_filename:           <RECEIVER>_<CONFIG>_<YYYY><DDD><HH>.TRACE
    output_residuals:           true
    output_residual_chain:      true
    output_config:              true

network_statistics:
    output:                     true                             # (bool) Enable exporting network statistics data to file
    directory:                  ./pod_network                          # (string) Directory to export network statistics data
    filename:                   <CONFIG>_network_statistics.json # (string) Network statistics data filename

gpx:
    output: true

sinex:
    output:                     true
    directory:                  ./pod_snx
    filename:                   <CONFIG>_<YYYY><DDD><HH>.SNX

sp3:
    output:                     true
    directory:                  ./pod_sp3
    filename:                   <CONFIG>_<YYYY><DDD><HH>.SP3
    output_interval:            30 # (int) Update interval for sp3 records

clocks:
    output:                     true
    directory:                  ./pod_clk
    filename:                   <CONFIG>_<YYYY><DDD><HH>.CLK

erp:
     output:                     true
     directory:                  ./pod_erp
     filename:                   <CONFIG>_<YYYY><DDD><HH>.ERP

orbex:
    output:                     true
    filename:                   <CONFIG>_<YYYY><DDD><HH>.OBX
    directory:                  ./pod_orbex
    attitude_sources:           [MODEL, NOMINAL]

satellite_options:

global:

    #clock_codes:                       [AUTO, AUTO]

    models:
        clock:
            enable:                    true
            sources:                   [KALMAN, PRECISE, BROADCAST]
        pos:
            enable:                    true
            sources:                   [KALMAN, PRECISE, BROADCAST]
        attitude:
            enable:                    true
            sources:                   [MODEL, PRECISE, NOMINAL]
        pco:
            enable:                    true
        pcv:
            enable:                    true
        code_bias:
            enable:                    true
            default_bias:              0
            undefined_sigma:           0
        phase_bias:
            enable:                    false
            default_bias:              0
            undefined_sigma:           0

    orbit_propagation:
        albedo:                   cannonball
        antenna_thrust:           true
        empirical:                true
        empirical_dyb_eclipse:    [true,false,false]
        planetary_perturbations:  [moon,sun,mercury,venus,mars,jupiter,saturn,uranus,neptune,pluto]
        pseudo_pulses:
            enable:               false
        solar_radiation_pressure: boxwing
        mass:                     1000
        area:                     15
        srp_cr:                   1.75
        power:                    20

GPS:
    clock_codes: [ L1W,L2W ]

# G04:
#     exclude:                           true
G15:
    exclude:                           true

E05: { exclude: true }
E06: { exclude: true }
E10: { exclude: true }
E16: { exclude: true }
E17: { exclude: true }
E23: { exclude: true }
E28: { exclude: true }
E29: { exclude: true }
E32: { exclude: true }
E34: { exclude: true }
E35: { exclude: true }

receiver_options: # Options to configure individual stations or global configs

USN7:
    aliases: [PIVOT]

global:

    error_model:                elevation_dependent         # uniform, elevation_dependent
    elevation_mask:             10
    code_sigma:                 0.4
    phase_sigma:                0.002
    clock_codes:                [AUTO, AUTO]
    zero_dcb_codes:             [NONE, NONE]
    models:
        eccentricity:
            enable:             true                            # (bool) Enable modelling of antenna eccentricities
        attitude:
            enable:             true                            # (bool) Enables non-nominal attitude types
            sources:            [MODEL, NOMINAL]       # List of sourecs to use for attitudes
        clock:
            enable:             true                            # (bool) Enable modelling of clocks
        pco:
            enable:             true                            # (bool) Enable modelling of phase center offsets
        pcv:
            enable:             true                            # (bool) Enable modelling of phase center variations
        code_bias:
            enable:             true                            # (bool) Enable modelling of code biases
            default_bias:       0                               # (float) Bias to use when no code bias is found
            undefined_sigma:    0                               # (float) Uncertainty sigma to apply to default code biases
        phase_bias:
            enable:             false                           # (bool) Enable modelling of phase biases
            default_bias:       0                               # (float) Bias to use when no phase bias is found
            undefined_sigma:    0                               # (float) Uncertainty sigma to apply to default phase biases
        pos:
            enable:             true                            # (bool) Enable modelling of position
        ionospheric_components:                                 # Ionospheric models produce frequency-dependent effects
            enable: true                                        # Enable ionospheric modelling
            use_2nd_order:  true
            use_3rd_order:  true
        troposphere:
            enable: true
            models: [gpt2]
        eop:
            enable: true

    apriori_sigma_enu:      [0.003, 0.003, 0.009]                 # Use these fixed igma'sfor sites listed below
    mincon_scale_apriori_sigma:  1                                # Use ALL fixed and/or SINEX file sigma's (!! first preference to the fixed sigma's !!)
    mincon_scale_filter_sigma:   0
#ABMF: {mincon_scale_apriori_sigma: 3 }
#ALBH: {mincon_scale_apriori_sigma: 3 }
#ALGO: {mincon_scale_apriori_sigma: 3 }

processing_options:

process_modes:
    preprocessor:                 true
    spp:                          true
    ppp:                          true
    ionosphere:                   false

epoch_control:
    epoch_interval:               30
    wait_next_epoch:              3600     # Wait up to an hour for next data point - When processing RINEX causes PEA to wait a long as need for last epoch to be processed.
    wait_all_receivers:           1

gnss_general:
    rec_reference_system:         gps
    minimise_sat_clock_offsets:   true
    sys_options:
        gps:
            process:              true
            ambiguity_resolution: false
            reject_eclipse:       false
            code_priorities:      [ L1W, L1C, L2W ]
        # gal:
        #     process:                true
        #     ambiguity_resolution:   false
        #     reject_eclipse:         false
        #     code_priorities:        [ L1C, L5Q, L1X, L5X ]
        # glo:
        #     process:                true
        #     ambiguity_resolution:   false
        #     reject_eclipse:         true
        #     code_priorities:        [ L1P, L1C, L2P, L2C ]
        # qzs:
        #     process:                true
        #     ambiguity_resolution:   false
        #     reject_eclipse:         true
        #     code_priorities:        [ L1C, L2L, L2X ]

spp:
    always_reinitialise: false
    max_lsq_iterations: 12
    outlier_screening:
        max_gdop: 30
        postfit:
            sigma_check: true

ppp_filter:
    ionospheric_components:
        common_ionosphere:        true
        use_if_combo:             false
    outlier_screening:
        prefit:
            max_iterations: 2
            sigma_check: true
            sigma_threshold: 5
            omega_test: false
        postfit:
            max_iterations: 10
            sigma_check: true
            sigma_threshold: 3

    rts:
        enable:                   true

model_error_handling:
    meas_deweighting:
        deweight_factor:          10000
    state_deweighting:
        deweight_factor:          10000
    ambiguities:
        outage_reset_limit:       3

        phase_reject_limit:       2
        reset_on:
            gf:    true
            lli:   true
            mw:    true
            scdia: true
    exclusions:
        gf:      true
        lli:     true
        mw:      true
        scdia:   true
        eclipse: false
    ionospheric_components:
        outage_reset_limit: 3
    orbit_errors:
        enable:                      false
        pos_process_noise:           10
        vel_process_noise:           1
        vel_process_noise_trail:     0
        vel_process_noise_trail_tau: 0

minimum_constraints:
    enable:                       true
    rotation:
        estimated:                [true]
    scale:
        estimated:                [true]
    translation:
        estimated:                [true]
    application_mode:             weight_matrix
    constrain_orbits:             false
    outlier_screening:                             # Statistical checks allow for detection of outliers that exceed their confidence intervals
        postfit:
            max_iterations:       10               # Maximum number of measurements to exclude using postfit checks while iterating filter
            sigma_check:          true             # Enable sigma check
            sigma_threshold:      3                # Sigma threshold
        prefit:
            max_iterations:       2                # Maximum number of measurements to exclude using prefit checks before attempting to filter
            omega_test:           false            # Enable omega-test
            sigma_check:          true             # Enable sigma check
            sigma_threshold:      5                # Sigma threshold

orbit_propagation:
    integrator_time_step:         60    # Timestep for the integrator, must be smaller than the processing time step, might be adjusted if the processing time step isn't a integer number of time steps
    central_force:                true
    egm_field:                    true  # Acceleration due to the high degree model of the Earth gravity model (exclude degree 0, made by central_force)
    egm_degree:                   15    # J2 acceleration perturbation due to the Sun and Moon
    solid_earth_tide:             true  # Model accelerations due to solid earth tides
    ocean_tide:                   true  # Model accelerations due to ocean tides model
    pole_tide_solid:              true  # Model accelerations due to solid pole tide (degree 2 only)
    pole_tide_ocean:              true
    general_relativity:           true
    indirect_J2:                  true

estimation_parameters:

global_models:
    eop:
        estimated:              [true]
        sigma:                  [10,10,1e-9]
    eop_rates:
        estimated:              [true]
        sigma:                  [10]

receivers:

    PIVOT:
        #clock:
        #    estimated:     [true]
        #    process_noise: [0]
        #    sigma:         [1e-9]
        code_bias:
            estimated: [false]

    global:
        pos:
            estimated:          [true]
            sigma:              [1]
            process_noise:      [0.0]
            # process_noise_dt:   second
        clock:
            estimated:          [true]
            sigma:              [1000]
            process_noise:      [10] # [100]
        ambiguities:
            estimated:          [true]
            sigma:              [1000]
            process_noise:      [0]
            # process_noise_dt:   day
        trop:
            estimated:          [true]
            sigma:              [0.3]
            process_noise:      [0.0001]
            # process_noise_dt:   second
        trop_grads:
            estimated:          [true]
            sigma:              [0.03]
            process_noise:      [1.0E-6]
            # process_noise_dt:   second
        ion_stec:
            estimated:          [true]
            sigma:              [500]
            process_noise:      [10]
        code_bias:
            estimated:          [true]
            sigma:              [20]
            process_noise:      [0]
    # USN7:
    #     clk:
    #         estimated:          [false]    # Set reference (pivot) station clock
    #     code_bias:
    #         estimated:          [false]

satellites:
    global:
        clock:
            estimated:          [true]
            sigma:              [1000]
            process_noise:      [1]
            tau:                [100]
            #mu:                 [10000]
        code_bias:
            estimated:          [true]
            sigma:              [10]
            process_noise:      [0]
        orbit:                                            # Orbital state
            estimated:          [true]                    # [bools] Estimate state in kalman filter
            sigma:              [10, 10, 10, 0.01]   # [floats] Apriori sigma values - if zero, will be initialised using least squares
            process_noise:      [0]

        emp_d_0: { estimated: [true], sigma: [10]}
        emp_y_0: { estimated: [true], sigma: [1]}
        emp_b_0: { estimated: [true], sigma: [1]}

        # emp_d_1: { estimated: [true], sigma: [1]}
        # emp_y_1: { estimated: [true], sigma: [1]}
        emp_b_1: { estimated: [true], sigma: [1]}

        emp_d_2: { estimated: [true], sigma: [1]}
        # emp_y_2: { estimated: [true], sigma: [1]}
        # emp_b_2: { estimated: [true], sigma: [1]}

        # emp_d_3: { estimated: [true], sigma: [1]}
        # emp_y_3: { estimated: [true], sigma: [1]}
        # emp_b_3: { estimated: [true], sigma: [1]}

        # emp_d_4: { estimated: [true], sigma: [1]}
        # emp_y_4: { estimated: [true], sigma: [1]}
        # emp_b_4: { estimated: [true], sigma: [1]}

mongo:

enable: primary

enable:                     none
output_components:          primary
output_states:              primary
output_measurements:        primary
output_test_stats:          none
output_trace:               none
delete_history:             primary

debug:

instrument: true

#output_mincon: true
#mincon_filename: preMinconState.bin
#mincon_only: true
# mincon_only: true

It was found that there was a large error in the orbit accuracy assessment. Are there any corrective measures? Among them I use https://github.com/GeoscienceAustralia/gnssanalysis for accuracy comparison

I found that the program performs backward Kalman data processing. How can I modify the pod.yaml file to improve the accuracy of orbit determination（do post-processing）?

[seballgeyer]

Hello,

I've reviewed the issues you're experiencing with the orbit accuracy assessment using the pod.yaml file and the sample data. It's clear that the inclusion of satellite G04, which was the first GPS BLK-IIIA SV and not fully operational at the time, has led to large errors.

The status of G04 as unhealth is detrimental to the accuracy of the orbit determination. Its exclusion is necessary to maintain the integrity of the data processing and to ensure the accuracy of the results.

For the backward Kalman data processing, please refer to the _smoothed files for detailed information on the backward smoothed run. To further improve the accuracy of orbit determination through post-processing, you will need to use those file in the comparison scripts.

Additionally, for the comparison script you are using, it would be beneficial to include the -h ECF option to correct a potential offset in the ECF reference frame of the orbits by fitting a Helmert transform. Also, using -n daily -n epoch to compare the clocks will help remove an epoch-wise and a daily offset. Implementing these options should enhance the results. Your updated command line would be :

orbq -i pod_example_201919900.SP3_smoothed  igs20624.sp3 -h ECF
clkq -i pod_example_201919900.CLK_smoothed  igs20624.clk_30s  -n daily -n epoch

I hope these recommendations will assist you in achieving more accurate orbit determinations. Should you need any more help, please don't hesitate to ask.

Best regards, Sebastien