Overview

This report covers GNSS+IMU integrated navigation systems applicable to hydrographic survey work in the global open commercial market, comprising 20 manufacturers and 56 models, divided into four classes: hydrographic POS, marine INS, subsea INS and OEM modules. Values are taken from current official manufacturer datasheets or product pages; unpublished items are marked as such, without back-calculation or conversion.

Accuracy figures are not comparable unless the correction source, statistical basis, antenna baseline and wave period are stated, so every table records its measurement conditions and cross-basis values serve only as tier references. On that foundation, five rankings are given for attitude, heading, heave, outage position hold and free inertial performance, together with summaries of interface protocols, correction services, alignment times and scenario suitability. Data cut-off is 12 August 2026.

1. Scope and Data Basis

1.1 Inclusion and Exclusion Criteria

Inclusion requires two conditions to hold simultaneously: the device itself contains both a GNSS receiver and an inertial measurement unit and outputs an integrated navigation solution; and the manufacturer’s public material explicitly lists at least one of hydrographic survey, hydrological survey, multibeam echosounding, uncrewed surface vessel or subsea survey work.

Table 1-1 Inclusion Categories and Criteria

Note: Model counts are based on independently named product models published by the manufacturer; depth-rating options and DVL frequency options of the same model are not counted separately.

The capability coverage of the four classes differs systematically, with Class G and Class O not providing published values for some indicators.

Table 1-2 Excluded Categories and Grounds for Exclusion

Note: Exclusion does not constitute an assessment of technical grade. The roll/pitch figures of standalone MRUs are comparable with the products in this report; the relevant values appear in the notes to Chapter 5.

1.2 Field Definitions

Table 1-3 Indicator Definitions Used in This Report

1.3 Differences in Statistical Basis

Manufacturers organize their performance tables inconsistently. Most high-end products list values by correction source, and figures for the same device can differ by a factor of 2 to 30 across columns. This report uniformly takes the RTK column, with the remaining columns listed separately in the corresponding chapters.

Table 1-4 Column Taken and Statistical Basis by Manufacturer

Note: Among the five statistical bases, CEP50 is the two-dimensional circular error probable, 1σ and RMS are one-dimensional standard deviations, 1DRMS is the two-dimensional distance root mean square, and TDRMS is the time-averaged distance root mean square. For the same true error distribution, a CEP50 figure is inherently smaller than a 1DRMS figure. Comparison of values across bases holds only at the tier level.

1.4 Data Confidence Grading

Table 1-5 Confidence Grade Definitions and Distribution in This Report

2. Product Classification

2.1 Classification Criteria

Classification rests on three dimensions: inertial sensor grade, operating medium and level of integration.

flowchart TD
    A["GNSS + IMU integrated navigation products"] --> B{"Contains a GNSS receiver"}
    B -->|No| X1["Excluded: standalone MRU / VRU<br/>Kongsberg MRU 5, Teledyne TSS DMS"]
    B -->|Yes| C{"Hydrographic use listed publicly"}
    C -->|No| X2["Excluded: naval INS, automotive-optimized models<br/>Safran Argonyx, OXTS RT3000"]
    C -->|Yes| D{"Attitude grade"}
    D -->|"0.5°-1.0° navigation-aid grade"| X3["Excluded: marine satellite compass<br/>Furuno SCX-20, JRC JLR-41"]
    D -->|"Better than 0.1° survey grade"| E{"Operating medium"}
    E -->|"Surface, MBES ecosystem"| H["Class H<br/>Hydrographic POS<br/>19 models"]
    E -->|"Surface, FOG/RLG denied-oriented"| M["Class M<br/>High-End Marine INS<br/>7 models"]
    E -->|"Subsea, INS+DVL"| G["Class G<br/>Subsea Survey INS<br/>9 models"]
    E -->|"Module level, integration required"| O["Class O<br/>OEM and Autonomous Platform<br/>21 models"]

Figure 2-1 Classification Criteria and Inclusion/Exclusion Path

Note: Products on the exclusion branches do not enter any subsequent ranking in this report.

2.2 Class Composition

pie showData title Share of models by class
    "Class O: OEM and Autonomous Platform" : 21
    "Class H: Hydrographic POS" : 19
    "Class G: Subsea Survey INS" : 9
    "Class M: High-End Marine INS" : 7

Figure 2-2 Share of Models by Class

Note: 56 models in total. Class O is the largest, reflecting that more manufacturers participate in the OEM module market than in the complete-system market.

2.3 Class Capability Matrix

Table 2-1 Capability Coverage of the Four Classes

Note: Class O generally provides no published values for heave or hydrographic protocols; that capability is implemented by the integrator at system level.

3. Manufacturer and Product Landscape

3.1 Distribution by Country

pie showData title Manufacturers by country
    "China" : 6
    "United States" : 4
    "Canada" : 2
    "France" : 2
    "Norway" : 1
    "United Kingdom" : 1
    "Australia" : 1
    "Belgium" : 1
    "Germany" : 1
    "Japan" : 1

Figure 3-1 Manufacturers by Country

Note: 20 manufacturers in total. China has the largest number of manufacturers, followed by the United States.

The distribution by model count differs from the distribution by manufacturer count, because a single European product line generally contains more performance variants.

xychart-beta
    title "Models by country"
    x-axis ["China", "France", "Canada", "Norway", "UK", "USA", "Australia", "Belgium", "Germany", "Japan"]
    y-axis "Number of models" 0 --> 16
    bar [14, 10, 7, 7, 6, 5, 4, 1, 1, 1]

Figure 3-2 Models by Country

Note: 56 models in total. All 7 Norwegian models are performance variants of a single Kongsberg product line, and all 6 UK models belong to the Sonardyne SPRINT-Nav family.

3.2 Distribution of Inertial Sensor Technology

pie showData title Inertial sensor technology by model count
    "MEMS" : 19
    "FOG" : 16
    "Not published or configuration-dependent" : 13
    "RLG" : 7
    "FOG/MEMS hybrid" : 1

Figure 3-3 Distribution of Inertial Sensor Technology

Note: Of the 13 models in the “not published or configuration-dependent” group, the four Applanix POS MV models do not publish the sensor type, the six Kongsberg Seapath 385 variants take either an MGC or a 5th-generation MRU inertial head according to the order configuration, and Hi-Target MS08 and MS12 do not state the sensor type.

3.3 Technology Route Against Accuracy Tier

Table 3-1 Best Published Roll/Pitch Value by Technology Route

Note: The 0.0025° of Exail Hydrins holds on the precondition of first navigating at least 30 minutes under available GNSS and completing two turns of more than 60°. The 0.010° of Sonardyne is a 1DRMS value under unaided conditions, a different source condition from the RTK-aided rows.

xychart-beta
    title "Best Roll/Pitch value by technology route (unit: 0.001 deg)"
    x-axis ["FOG", "Not published", "RLG", "MEMS"]
    y-axis "Roll/Pitch (0.001 deg)" 0 --> 16
    bar [2.5, 3, 10, 15]

Figure 3-4 Best Roll/Pitch Value by Technology Route

Note: The vertical axis unit is 0.001°. The RLG value is higher than the FOG value because all RLG models in this report are subsea products whose manufacturers publish under unaided conditions; this is not a difference in sensor capability.

3.4 Manufacturer and Product Line Overview

Table 3-2 Manufacturer, Country and Product Line

Note: The acquisition of Inertial Labs by VIAVI Solutions was announced in December 2024 and completed in the first quarter of 2025. The relevant Kongsberg business unit is now named Kongsberg Discovery. Exail was formed by the 2022 merger of ECA Group and iXblue.

4. Core Performance Parameter Table

4.1 How the Parameter Table Is Read

Table 4-1 Value Selection Rules for the Parameter Table

4.2 Core Model Parameter Table

Table 4-2 Unified Parameters of Core Hydrographic Integrated Navigation Models

Note 1: The 0.0025° of Exail Hydrins holds on the precondition stated in the datasheet footnote — first navigating at least 30 minutes under available GNSS (1 m standard deviation) and completing two turns of more than 60°. The value is not attained immediately after power-on.

Note 2: The entire Kongsberg Seapath 385 range is published against a fixed 4 m antenna baseline, with no 2 m column. SBG Navsight Horizon publishes only the 2 m column, with no 4 m column.

Note 3: The outage values of the Sonardyne and Exail subsea models are CEP50 under fully unaided conditions, a different source condition from the 1σ/RMS values of surface models entering outage from RTK; the two groups cannot be compared directly by magnitude.

Note 4: The 3 m of SBG Navsight Ekinox corresponds to a 30-second outage, not 60 seconds; the reason appears in 8.6.

Note 5: Two sets of published attitude figures exist for the Honeywell HGuide n580 (superseded values Roll/Pitch <0.015°, Heading <0.03°; current published values Pitch/Roll 0.01°, Heading 0.05°). Determining which set corresponds to the current hardware version is not possible, so under the data principle neither set is used and this model does not enter any ranking in this report.

Note 6: The R of ComNav K825 denotes the dual-antenna baseline length in metres. A 2 m baseline corresponds to Heading 0.075° and Roll/Pitch 0.15°.

5. Attitude Accuracy

5.1 Roll/Pitch Ranking

The ranking admits real-time values only; post-processed values are not merged in. The measurement condition is RTK or GNSS-aided, with unaided values of subsea models marked separately.

            Real-time Roll/Pitch accuracy (degrees, lower is better)
                                      0.020   0.040   0.060   0.080   0.100
                                        │       │       │       │       │
 1  Exail Hydrins        0.0025  ▌                                         [A] GNSS-aided, 30 min convergence
 2  POS MV Elite         0.003   ▌                                         [A] IARTK, 1σ
 3  Boreas D90           0.005   ██                                        [B] RTK
 3  Seapath 385-5+/R4    0.005   ██                                        [A] RTK, RMS
 5  Seapath 385-R3       0.007   ███                                       [A] RTK, RMS
 5  SBG Horizon          0.007   ███                                       [A] RTK
 7  iPos MS08            0.008   ███                                       [B] RTK, 1σ
 7  SBG Apogee           0.008   ███                                       [A] RTK
 7  Seapath 385-5/60     0.008   ███                                       [A] RTK, RMS
10  POS MV OceanMaster   0.010   ████                                      [A] IARTK, 1σ
10  Seapath 385-3/40     0.010   ████                                      [A] RTK, RMS
10  iPos MS11            0.010   ████                                      [B] RTK, 1σ
10  SPRINT-Nav I/S/X     0.010   ████                                      [A] unaided, 1DRMS
10  Phins Subsea/Rovins  0.010   ████                                      [A] unaided, RMS
10  Boreas D70           0.010   ████                                      [B] RTK
16  SBG Ekinox           0.015   ██████                                    [A] RTK
17  POS MV WaveMaster II 0.020   ████████                                  [A] IARTK, 1σ
17  iPos MS12            0.020   ████████                                  [B] RTK, 1σ
19  POS MV SurfMaster    0.030   ████████████                              [B] IARTK, 1σ
19  iPos MS13            0.030   ████████████                              [B] RTK, 1σ
19  Certus Evo           0.030   ████████████                              [B] RTK
22  VectorNav VN-300     0.100   ████████████████████████████████████████  [A] dynamic RMS

Figure 5-1 Real-Time Roll/Pitch Accuracy Ranking

Note: Bar lengths are drawn linearly against the values, one cell representing 0.0025°. The horizontal scale marks share that scale, and the end of each bar falls exactly on its corresponding mark, so bars can be read against the scale directly. The bracketed letter is the confidence grade, followed by the measurement condition. The first and last entries differ by a factor of 40.

5.2 Accuracy Tiers

Table 5-1 Roll/Pitch Accuracy Tiers

Note: The Sonardyne and Exail subsea models in Tier 3 are published under unaided conditions and are no worse than those values under aided conditions; their tier placement is affected by the published basis.

5.3 Mechanism by Which Attitude Error Affects Lateral Position

The relationship between outer-beam lateral position error and attitude error is:

Lateral error = slant range × tan(attitude error)

Results calculated from that expression follow.

xychart-beta
    title "Outer-beam lateral error from attitude error (slant range 200 m)"
    x-axis ["0.0025°", "0.005°", "0.010°", "0.020°", "0.030°", "0.050°", "0.100°"]
    y-axis "Lateral error (cm)" 0 --> 36
    line [0.87, 1.75, 3.49, 6.98, 10.47, 17.45, 34.91]
    bar [0.87, 1.75, 3.49, 6.98, 10.47, 17.45, 34.91]

Figure 5-2 Attitude Error Against Lateral Position Error (Slant Range 200 m)

Note: The values are geometric quantities calculated directly from the expression above; they are derived figures, not manufacturer-published values. A slant range of 200 m corresponds approximately to the outer beam at 100 m water depth and ±60° swath angle.

Table 5-2 Lateral Error at Different Slant Ranges (unit: cm)

Note: The entire table consists of values derived from the geometric formula. This error is only one component of total propagated uncertainty; actual product accuracy is further affected by positioning, sound velocity profile, tide, draft and mounting-angle calibration residuals.

5.4 Distinction Between Aided and Unaided Bases

Table 5-3 Grouping of Attitude Values by Measurement Condition

Note: Values under the three conditions do not form a strictly comparable set. Unaided values do not degrade under aided conditions, so the actual capability of the third group is no lower than the values in the table.

6. Heading Accuracy

Dual-antenna heading accuracy is directly related to baseline length, and a heading figure without a stated baseline carries no comparative meaning.

6.1 Ranking at 2 m Baseline

              Dual-antenna heading accuracy @2 m baseline (degrees)
                                     0.020   0.040   0.060   0.080
                                       │       │       │       │
 1  SBG Horizon          0.010  ████                              [A]
 2  POS MV Elite         0.015  ██████                            [A]
 3  POS MV OceanMaster   0.020  ████████                          [A]
 3  SBG Apogee           0.020  ████████                          [A]
 3  iPos MS08            0.020  ████████                          [B]
 6  POS MV WaveMaster II 0.030  ████████████                      [A]
 6  SBG Ekinox           0.030  ████████████                      [A]
 6  iPos MS11            0.030  ████████████                      [B]
 9  iPos MS12            0.060  ████████████████████████          [B]
10  iPos MS13            0.080  ████████████████████████████████  [B]
10  Bynav X1-7H          0.080  ████████████████████████████████  [B]

Figure 6-1 Dual-Antenna Heading Accuracy Ranking (2 m Baseline)

Note: One cell represents 0.0025°, and the end of each bar falls exactly on its corresponding scale mark. The entire Kongsberg Seapath 385 range publishes only 4 m baseline values and does not appear in this figure.

6.2 Ranking at 4 m Baseline

              Dual-antenna heading accuracy @4 m baseline (degrees)
                                     0.020   0.040   0.060
                                       │       │       │
 1  Seapath 385-R4       0.007  ███                       [A]
 2  POS MV Elite         0.008  ███                       [A]
 3  Seapath 385-R3       0.010  ████                      [A]
 3  POS MV OceanMaster   0.010  ████                      [A]
 3  SBG Apogee           0.010  ████                      [A]
 3  iPos MS08            0.010  ████                      [B]
 7  POS MV WaveMaster II 0.015  ██████                    [A]
 7  iPos MS11            0.015  ██████                    [B]
 9  Seapath 385-5+/R2    0.020  ████████                  [A]
 9  SBG Ekinox           0.020  ████████                  [A]
11  iPos MS12            0.030  ████████████              [B]
11  Seapath 385-5/60     0.030  ████████████              [A]
13  Bynav X1-7H          0.050  ████████████████████      [B]
13  Seapath 385-3/40     0.050  ████████████████████      [A]
15  iPos MS13            0.060  ████████████████████████  [B]

Figure 6-2 Dual-Antenna Heading Accuracy Ranking (4 m Baseline)

Note: One cell represents 0.0025°, and the end of each bar falls exactly on its corresponding scale mark. SBG Navsight Horizon publishes only 2 m baseline values and does not appear in this figure. The leading model differs between the two rankings, which shows that baseline length has a decisive effect on placement.

6.3 Effect of Baseline Length

Published values of the same model at the two baselines compare as follows.

xychart-beta
    title "Heading accuracy at 2 m vs 4 m baseline, same model (unit: 0.001 deg)"
    x-axis ["POS MV Elite", "OceanMaster", "WaveMaster II", "SBG Apogee", "SBG Ekinox", "iPos MS08", "iPos MS11", "iPos MS12", "iPos MS13"]
    y-axis "Heading (0.001 deg)" 0 --> 85
    bar [15, 20, 30, 20, 30, 20, 30, 60, 80]
    line [8, 10, 15, 10, 20, 10, 15, 30, 60]

Figure 6-3 Effect of Baseline Length on Heading Accuracy

Note: Bars are 2 m baseline values and the line is 4 m baseline values, both in units of 0.001°. Eight of the nine models improve by roughly a factor of two when the baseline is doubled; SBG Ekinox improves by a factor of 1.5.

Table 6-1 Improvement Factor from Doubling the Baseline

Note: The improvement factor is the 2 m value divided by the 4 m value, obtained directly from the two published columns. In practice, baseline length is constrained by hull flexure, antenna mast deformation, multipath and baseline calibration error.

6.4 Distinction Between Dual-Antenna Heading and Gyrocompassing

Table 6-2 Comparison of the Two Heading Sources

Note: secLat is the reciprocal of the cosine of latitude. At 60° latitude, secLat equals 2 and the north-seeking heading error is twice the nominal value.

6.5 Gyrocompassing Capability Ranking

                                 Gyrocompass heading accuracy (degrees secLat)
                          0.010   0.025  0.040 0.050        0.100
                            │       │      │     │            │
 1  Boreas D90       0.010  ████                                      [B] GNSS-free north-seeking
 1  SPRINT-Nav X     0.010  ████                                      [A] dual-aided, 1DRMS
 1  Phins Subsea     0.010  ████                                      [A] GNSS/USBL/LBL and DVL
 4  SPRINT-Nav S     0.025  ██████████                                [A] dual-aided
 4  Phins Subsea     0.025  ██████████                                [A] single aiding source
 6  SPRINT-Nav S     0.030  ████████████                              [A] single-aid
 7  SPRINT-Nav I     0.040  ████████████████                          [A] dual-aided
 7  Exail Rovins     0.040  ████████████████                          [A] dual-aided
 9  SPRINT-Nav I     0.050  ████████████████████                      [A] single-aid
 9  Exail Hydrins    0.050  ████████████████████                      [A] gyro-only, no GNSS
11  Exail Rovins     0.070  ████████████████████████████              [A] single-aid
12  Boreas D70       0.100  ████████████████████████████████████████  [B] GNSS-free north-seeking

Figure 6-4 Gyrocompass Heading Accuracy Ranking

Note: This figure contains two bases. The Boreas and Hydrins values are north-seeking accuracy with no external aiding; the Sonardyne and Exail subsea values are heading-hold accuracy with DVL, USBL or LBL aiding. The two bases answer different capability questions, and their arrangement in one figure serves only to show orders of magnitude.

7. Heave Measurement

Heave accuracy carries no comparative meaning apart from the applicable wave-period limit. A device rated at 1 cm but guaranteed only to a 10 s period does not necessarily outperform a device rated at 5 cm and guaranteed to a 20 s period under a 20 s long swell.

7.1 Real-Time Heave Ranking

                        Real-time heave accuracy and applicable wave period
                                   Accuracy (cm)                Wave period limit
 1  Seapath 385-5/60 and above  1 cm/1%   ██              ≤10 s          [A]
 2  Boreas D70/D90              2 cm/2%   ████            Not published  [B]
 2  Seapath 385-3/40            2 cm/2%   ████            ≤10 s          [A]
 4  SBG Navsight, all models    5 cm      ██████████      ≤20 s          [A]
 4  POS MV, all models          5 cm/5%   ██████████      ≤20 s          [A]
 4  Exail Hydrins               5 cm/5%   ██████████      ≤25 s          [A]
 4  SPRINT-Nav I/S/X            5 cm/5%   ██████████      ≤10 s          [A]
 4  Hi-Target iPos MS, all      5 cm/5%   ██████████      Not published  [B]

Figure 7-1 Real-Time Heave Accuracy Ranking

Note: Boreas D70/D90 is the only model in this figure with no published wave-period limit; its 2 cm value does not form a strictly comparable relationship with the 1 cm (≤10 s) of Seapath.

7.2 Two-Dimensional Relationship Between Accuracy and Wave Period

xychart-beta
    title "Real-time heave: accuracy value and wave period limit"
    x-axis ["Seapath 5/60+", "Seapath 3/40", "SPRINT-Nav", "SBG Navsight", "POS MV", "Exail Hydrins"]
    y-axis "Accuracy (cm) and period (s)" 0 --> 28
    bar [1, 2, 5, 5, 5, 5]
    line [10, 10, 10, 20, 20, 25]

Figure 7-2 Two-Dimensional Distribution of Real-Time Heave Accuracy and Wave Period Limit

Note: Bars are accuracy values (cm) and the line is the wave-period limit (s). A model with a lower bar and a higher line performs better overall under long-period swell. Boreas is absent from this figure because its period is not published.

7.3 Delayed Heave Comparison

Table 7-1 Comparison of Delayed Heave Implementations

Note: Delayed heave re-estimates the low-frequency heave component using data acquired after the epoch in question, and is superior to real-time heave in both accuracy and applicable period. Applanix public material states that TrueHeave requires no filter tuning for specific sea states and has no settling time, so no run-in line is needed.

7.4 Constraint Imposed by Latency on Application Scenarios

Table 7-2 Scenario Fit of Delayed Heave

Note: The 100 s fixed latency of Exail Smart Heave imposes no limitation in post-processed charting and constitutes an exclusion criterion in real-time control loops.

8. GNSS Outage Position Hold

Surface models and subsea models publish outage figures on different bases. Surface models publish the horizontal position error after entering outage from an RTK state; subsea models publish CEP50 under fully unaided conditions. The two groups cannot be compared directly by magnitude.

8.1 Surface Model 60-Second Outage Ranking

     Horizontal position error after 60 s outage entered from RTK (metres)
                                  1   2       4       6       8
                                  │   │       │       │       │
 1  Seapath 385-R4       0.08  █                                     [A] RMS
 2  Seapath 385-R3        0.2  █                                     [A] RMS
 3  Seapath 385-5+        0.3  █                                     [A] RMS
 3  Exail Hydrins        0.30  █                                     [A] RMS
 5  POS MV Elite         ~0.5  ██                                    [A] 1σ
 6  Seapath 385-R2        0.6  ██                                    [A] RMS
 6  Seapath 385-5/60      0.6  ██                                    [A] RMS
 8  SBG Horizon           1.0  ████                                  [A] Not stated
 9  Seapath 385-3/40      1.6  ███████                               [A] RMS
10  iPos MS08             2.5  ██████████                            [B] 1σ
11  POS MV OceanMaster     ~3  ████████████                          [A] 1σ
11  iPos MS11               3  ████████████                          [B] 1σ
13  SBG Apogee              4  ████████████████                      [A] Not stated
14  iPos MS12               6  ████████████████████████              [B] 1σ
15  POS MV WaveMaster II   ~9  ████████████████████████████████████  [A] 1σ
15  iPos MS13               9  ████████████████████████████████████  [B] 1σ

Figure 8-1 Surface Model 60-Second Outage Position Error Ranking

Note: One cell represents 0.25 m, and the end of each bar falls exactly on its corresponding scale mark. The first and last entries differ by a factor of 112, so the four models below 1 m all compress to a single cell on a linear scale; the value column governs for those entries. The 3 m of SBG Navsight Ekinox corresponds to a 30-second outage and is not merged into this figure.

8.2 Subsea Model Unaided Ranking

                        Position error with no external aiding (metres, CEP50)
                        0.06  0.2   0.3    0.5           1.2
                          │    │     │      │             │
 1  Exail Phins Subsea  0.06  ▌                                    [A] 60 s
 2  Exail Rovins        0.2   ███                                  [A] 60 s
 3  SPRINT-Nav X        0.3   █████                                [A] 60 s
 4  SPRINT-Nav S        0.5   ████████                             [A] 60 s
 5  SPRINT-Nav I        1.2   ████████████████████                 [A] 60 s

Figure 8-2 Subsea Model 60-Second Unaided Position Error Ranking

Note: All values are on a CEP50 basis. Exail publishes 120-second values as well; Sonardyne does not publish 120-second values.

8.3 Relationship Between Outage Duration and Error Growth

xychart-beta
    title "Growth of position error against outage duration"
    x-axis ["0 s", "30 s", "60 s", "120 s"]
    y-axis "Position error (m)" 0 --> 4.5
    line [0.01, 0.03, 0.06, 0.3]
    line [0.01, 0.09, 0.2, 0.6]
    line [0.01, 1.2, 4, 4]

Figure 8-3 Growth of Position Error Against Outage Duration

Note: The three curves from bottom to top are Exail Phins Subsea (60 s 0.06 m, 120 s 0.3 m), Exail Rovins (60 s 0.2 m, 120 s 0.6 m) and SBG Navsight Apogee (60 s 4 m). Apart from Apogee, the points at 30 s are interpolated for illustration and are not manufacturer-published values. Phins Subsea grows by a factor of 5 from 60 s to 120 s and Rovins by a factor of 3; both are non-linear, so outage values for different durations cannot be linearly extrapolated.

Table 8-1 Models Publishing Two Durations

Note: The growth factors of the two models differ, which shows that the error growth rate is related to inertial sensor grade and cannot be converted with a single coefficient.

8.4 Effect of Outage on Attitude

The degradation of position and of attitude during an outage differs by an order of magnitude.

Table 8-2 Attitude Before and After a 60-Second Outage

Note: The current Kongsberg datasheet states “Roll, pitch, heading and heave are unaffected by a 60-second GNSS dropout”. The position error of POS MV Elite grows by roughly a factor of 50 after a 60-second outage, while Roll/Pitch grows by roughly a factor of 13 and Heading by roughly a factor of 2. That difference indicates that the principal effect of a short outage on multibeam products is an overall translation rather than distortion of the beam fan.

8.5 Long-Term Free Inertial and DVL Aiding

                    Long-term free-inertial position hold (time to 1 nmi)
 SPRINT-Nav X     ████████████████████████████████  8 hours       [A] CEP50
 SPRINT-Nav S     ██████████                        2.5 hours     [A] CEP50
 SPRINT-Nav I     ███                               45 minutes    [A] CEP50

Figure 8-4 Long-Term Free-Inertial Position Hold Capability

Note: Bar lengths are drawn linearly against duration. Naval-grade INS products are excluded from this report because their application is not survey; their figures span 1 nmi over 4 to 72 hours.

Table 8-3 Position Drift Under DVL Aiding

Note: %TD denotes a percentage of travelled distance. The DVL-aided figures of surface INS and dedicated subsea INS differ by an order of magnitude, because the role of the DVL differs between the two product types — in a surface INS the DVL supplements short GNSS interruptions, whereas in a subsea INS the DVL is the primary navigation source.

8.6 30-Second Values Cannot Be Linearly Extrapolated to 60 Seconds

The outage value published by SBG Navsight Ekinox is 3 m under a 30-second condition. Growth of inertial error over time is a non-linear process, and the measured data in Section 8.3 show growth factors between 3 and 5 that vary by model. The 3 m at 30 seconds therefore cannot be converted into 6 m at 60 seconds, and this model is not listed in the ranking in Section 8.1.

9. Initialization and Alignment Time

9.1 Time Indicators

xychart-beta
    title "Initialization and alignment time (seconds)"
    x-axis ["K825 reacquisition", "K825 RTK init", "K825 hot start", "K825 cold start", "X1 warm start", "X1 cold start", "SPAN static coarse", "Boreas gyrocompass", "SPRINT-Nav DVL align"]
    y-axis "Time (s)" 0 --> 320
    bar [1, 5, 10, 20, 30, 45, 45, 120, 300]

Figure 9-1 Initialization and Alignment Time

Note: All values are manufacturer-published upper limits. The 45 s SPAN static coarse alignment applies to IMUs capable of sensing Earth rotation and does not apply to the CPT7; the explanation appears in Section 9.2.

Table 9-1 Initialization and Alignment Time Detail

9.2 Applicability of Alignment Methods

Table 9-2 Alignment Methods and Applicable Conditions

Note: NovAtel OEM7 official documentation states that HG4930-class IMUs cannot complete a static coarse alignment because gyroscopes of that grade cannot accurately sense Earth rotation. The NovAtel CPT7 uses precisely the HG4930, and its default alignment method is kinematic alignment. The CPT7 therefore cannot complete alignment while stationary alongside, and requires either entry into a navigating state or a dual-antenna configuration.

9.3 Distinction Between Completed Alignment and Attained Nominal Accuracy

The NovAtel SPAN official manual divides the states as follows: navigation mode is entered once coarse alignment is complete, IMU errors continue to be estimated through vehicle manoeuvre, and full specification is attained after filter convergence.

Alignment time and time to attain nominal accuracy are therefore two different indicators. The 0.0025° of Exail Hydrins requiring 30 minutes of navigation plus two turns of more than 60° is a concrete instance of that distinction. Manufacturer-published alignment times all refer to the former.

10. Interface Protocols and Time Synchronization

10.1 Protocol Capability Levels

Table 10-1 Definition of Protocol Capability Levels

Note: Hydrographic telegrams include TSS, Simrad, EM3000 and Kongsberg/Seatex formats. Level 4 adds PPS, PTP, Event Mark, and raw GNSS and raw IMU logging.

10.2 Protocol Support Matrix

Table 10-2 Protocol Support of Principal Models

Note: Exail publishes support for more than 130 output protocols across its range. Class O products generally provide no hydrographic telegrams; that part is implemented by the integrator at system level.

10.3 Output Rate

xychart-beta
    title "Maximum attitude data output rate (Hz)"
    x-axis ["Boreas D70/D90", "iPos MS all", "VN-300", "POS MV", "Seapath 385", "Exail Hydrins", "SPAN CPT7", "HGuide n580", "CGI-610", "K825"]
    y-axis "Output rate (Hz)" 0 --> 1050
    bar [1000, 500, 400, 200, 200, 200, 200, 100, 100, 20]

Figure 10-1 Maximum Attitude Data Output Rate

Note: The 400 Hz of the VN-300 is the run rate of the built-in extended Kalman filter. The output range of Exail Hydrins is continuously configurable from 0.1 Hz to 200 Hz. Maximum NMEA output is 50 Hz for Hi-Target iPos MS and 50 Hz for POS MV.

10.4 Time Synchronization Accuracy

Table 10-3 Time Synchronization Capability

Note: The 20 ns of ComNav K825 is a timing accuracy figure. That model is an OEM module, and the definition does not fully coincide with the 1PPS output accuracy figure of complete systems.

10.5 Capability Boundary of Standard NMEA

The traditional NMEA sentences GGA, RMC and HDT were designed for low-rate navigation. The data items required for multibeam echosounding include attitude at 100 Hz to 500 Hz, precise timestamps, angular rate, heave, velocity, quality flags and latency; the standard NMEA sentence set does not cover the last four.

The typical architecture of Level 3 and Level 4 products is therefore three parallel output paths: NMEA for navigation and compatible equipment, manufacturer binary for multibeam acquisition software, and PPS or PTP for system-wide time synchronization.

11. GNSS Correction Service Support

Performance tables of high-end products are listed by correction source, and position accuracy of the same model can differ by more than a factor of 30 across correction sources. Availability of correction services in the operating area directly determines the position accuracy actually attained.

11.1 Types of Correction Source

Table 11-1 Definition of Correction Source Types

Note: Among commercial PPP services, Fugro Marinestar has the widest installed base in the marine sector and offers multiple grades including G4 and G4+; Veripos Apex targets the offshore dynamic positioning market; Trimble CenterPoint RTX Marine is natively supported by POS MV.

11.2 Correction Source Support by Model

Table 11-2 Correction Source Support and Corresponding Accuracy

Note: The POS MV performance table has seven columns: DGNSS, Fugro Marinestar, IARTK, POSPac PPP, POSPac IAPPK, 60 s outage and CenterPoint RTX Marine. The Seapath 385 performance table has five columns: non-differential, Galileo HAS, RTK, real-time PPP and dead reckoning 60 s.

11.3 Magnitude of the Correction Source Effect

xychart-beta
    title "Exail Hydrins horizontal position accuracy by correction source (cm)"
    x-axis ["RTK/PPK", "PPP", "DGNSS", "SPS standalone"]
    y-axis "Horizontal accuracy (cm)" 0 --> 130
    bar [0.6, 6, 30, 120]

Figure 11-1 Span of Position Accuracy Across Correction Sources for One Model

Note: Taking Exail Hydrins as the example, horizontal accuracy differs by a factor of 200 between the best and worst correction sources. The corresponding span for Kongsberg Seapath 385 runs from RTK 0.01 m to non-differential 0.3 m, a factor of 30.

11.4 Non-Differential Positioning Capability

The published non-differential horizontal accuracy of Kongsberg Seapath 385 is 0.3 m, described in the datasheet as a unique high-precision non-differential position algorithm. That figure indicates that the bare positioning accuracy of a modern high-end POS has reached the decimetre level with the correction link completely interrupted.

For shallow-water echosounding, a horizontal error of 0.3 m falls within the acceptable range in most cases. Assurance of the vertical datum relies on tide observation or GNSS height combined with a geoid model, and is not covered by this figure.

12. Overall Tiers and Scenario Suitability

12.1 Overall Tiers

Table 12-1 Overall Tiers by Published Indicators

Note: Tier assignment rests on the completeness and values of published indicators, and excludes price, delivery lead time and service capability factors.

12.2 Scenarios and Capability Requirements

Table 12-2 Key Indicator Thresholds by Operating Scenario

Note: In scenarios where attitude accuracy is not the dominant error source, further improvement yields limited benefit to the final product.

12.3 Scenarios and Candidate Models

Table 12-3 Candidate Models by Scenario

Note: Indicators differ markedly between Kongsberg Seapath 385 variants — heading differs by a factor of 7 and 60-second outage by a factor of 20 between 385-R4 and 385-3/40 — so selection is confirmed against the specific variant.

12.4 Publication Status of Chinese Models

Table 12-4 Indicator Publication Completeness of Chinese Models

Note: The Bynav X9 series publishes sensor-level figures such as gyro bias instability (X910 ≤0.015°/h, X904 and X906 ≤0.05°/h, X903 ≤0.1°/h) and does not publish the four hydrographic system-level indicators. No convertible relationship exists between sensor-level and system-level figures.

xychart-beta
    title "Hi-Target iPos MS vs international peers, Roll/Pitch (0.001 deg)"
    x-axis ["POS MV Elite", "iPos MS08", "SBG Apogee", "iPos MS11", "POS MV OceanMaster", "iPos MS12", "POS MV WaveMaster II", "iPos MS13", "POS MV SurfMaster"]
    y-axis "Roll/Pitch (0.001 deg)" 0 --> 32
    bar [3, 8, 8, 10, 10, 20, 20, 30, 30]

Figure 12-1 Comparable Indicators of Chinese and International Peer Models

Note: Only Chinese models with all four hydrographic indicators published are included. The four models of the Hi-Target iPos MS series sit in the same value tiers as SBG Apogee, Applanix POS MV OceanMaster, WaveMaster II and SurfMaster respectively.

12.5 Effect of Publication Completeness

Some high-end Chinese models publish gyro bias, accelerometer bias, RTK accuracy and an interface list, but lack Roll/Pitch under marine conditions, 60-second outage, delayed heave and sea trial data. Without those indicators, inclusion in the horizontal rankings of this report is not possible.

That situation reflects a difference in the completeness of published material and does not constitute an assessment of actual product performance.

13. Data Sources and Versions

13.1 Documents Underlying Grade A Data

Table 13-1 Datasheet Versions Underlying Grade A Data

Note: Values may differ between documents of the same name under different version numbers; the versions listed in this table govern any re-check.

13.2 Official Manufacturer Sources

Table 13-2 Official Manufacturer Entry Points

13.3 Update Notes

The retrieval date of this report is 2026-08-12. Manufacturer specifications are updated continuously, and the procurement stage involves downloading the latest datasheet for the corresponding hardware version afresh and checking it against the version numbers listed in Table 13-1.

The Kongsberg website path has migrated from kongsberg.com/what-we-do/ocean-space/inertial-solutions/ to kongsberg.com/discovery/. The Applanix direct link applanix.com/downloads/products/specs/posmv/ is no longer valid, and the current datasheet is obtained through the product page.

Appendix A: Complete Parameter Database

Grouped by manufacturer, one row per model. Gaps are marked “Not published” under the data principle.

Table A-1 Complete Parameters of Class H Hydrographic POS

Note: The complete parameters of Kongsberg Seapath 130 are not published alongside the 385 series in the current datasheet and are not included in this table. Exail Hydrins supports single-antenna heading and has no dual-antenna baseline configuration.

Table A-2 Complete Parameters of Class M High-End Marine INS and Class G Subsea Survey INS

Note: The gyrocompass heading column for SPRINT-Nav takes the dual-aided value; single-aid values appear in Section 6.5. Position values for Sonardyne and Exail are all CEP50. Heave for the entire SPRINT-Nav range is 5 cm or 5% with an applicable wave period ≤10 s. Export of SPRINT-Nav is not ITAR controlled, and Exail products are marked ITAR-free.

Table A-3 Complete Parameters of Class O OEM and Autonomous Platform Modules

Note: The R of ComNav K825 denotes the dual-antenna baseline length in metres. Gyro bias figures for the Bynav X9 series are values under room temperature with 10 s smoothing. No convertible relationship exists between sensor-level bias figures and system-level accuracy.

Appendix B: Data Confidence Grading

B.1 Grade Definitions

Table B-1 Confidence Grades

B.2 Grade Distribution of Data in This Report

pie showData title Confidence distribution of models listed in Appendix A
    "Grade B: manufacturer web page" : 31
    "Grade A: current official datasheet" : 19
    "Not stated: model- or configuration-dependent" : 5

Figure B-1 Confidence Distribution of Core Parameter Data

Note: The statistical population is the 55 models actually listed in the three tables of Appendix A (the complete parameters of Kongsberg Seapath 130 are not published alongside the 385 series and do not enter the Appendix A tables, so 55 of the 56 models are listed). The 5 models in the “not stated” group are the iMAR iNAT series and Exail Phins Compact, Atlans, Octans and Quadrans, whose parameters vary with the specific model. All rankings use only Grade A and Grade B data.

B.3 Rules for Handling Conflicting Data

Table B-2 Treatment of Data Conflicts

B.4 Statistics on Unpublished Items

Table B-3 Publication Status of the Four Core Hydrographic Indicators

Note 1: The statistical base is 56 models. The criterion for “published” is the presence of an explicit value; qualitative expressions such as “configuration-dependent”, “model-dependent” and “available” count as not published.

Note 2: The 18 listed Class H models have publication rates of 89% to 100% across the four indicators, while the 21 Class O models have a publication rate of 0 for real-time heave and 60-second outage. The low overall rate is driven mainly by Class O, where that capability is implemented and verified by the integrator at system level.

Note 3: SBG Navsight Ekinox publishes a 30-second outage value and counts as not published under the 60-second outage item. Honeywell HGuide n580 counts as not published under Roll/Pitch and Heading because of the conflict between superseded and current values.