maritime-schema

Python package containing data classes and corresponding JSON schemata for common types used in generating traffic scenarios and testing of autonomous navigation systems.

The data classes in the package are implemented as data models using the pydantic framework.

All data classes reside in subpackage maritime_schema.types.caga and can be imported from there.

Installation

pip install maritime-schema

Getting Started

Creating an Input Schema File (Traffic Situation)

This section will guide you through the process of creating a traffic situation using this package.

Creating a Ship

Let's start by defining static information relating to a ship - information which will not change during the scenario. This includes things such as length, the ship type, name, and MMSI and IMO numbers. We will define static information using the ShipStatic class.

• Each ship must have a unique id, in the form of a UUID. For this, the uuid module from the standard library can be used.
• The GeneralShipType class lists several general ship types, similar to those found in AIS.
• Note that some of these fields (such as MMSI & IMO) can be left as None, as not all ships are required to have this data.

from maritime_schema.types.caga import ShipStatic, GeneralShipType
from uuid import uuid4

my_own_ship_static = ShipStatic(
    id=uuid4(),
    length=200, width=30, height=10,
    ship_type=GeneralShipType.FISHING,
    speed_max=20,
    name="Starfish 2",
    mmsi=None, imo=None,
)

Next, we can define the initial conditions for this ship, using the Initial and Position classes.

The AISNavStatus class is used to set the nav_status of the ship. This contains several navigational statuses from AIS.

from maritime_schema.types.caga import Initial, Position, AISNavStatus

initial_state = Initial(
    position=Position(latitude=58.61, longitude=10.59),
    sog=10, cog=100, heading=200,
    nav_status=AISNavStatus.UNDER_WAY_USING_ENGINE
)

Now, let's put it all together into an OwnShip object. An OwnShip has static information, an initial state, and could also have waypoints. However, in this simple example, waypoints will be set to None.

from maritime_schema.types.caga import OwnShip

own_ship = OwnShip(static=my_own_ship_static, initial=initial_state, waypoints=None)

The exact same process can be used to create target ships. However, instead of using the OwnShip class, the TargetShip class. should be used.

Creating the Traffic Situation

Let's put the own_ship we just created into a traffic situation.

import datetime
from maritime_schema.types.caga import TrafficSituation

traffic_situation = TrafficSituation(
    title="example situation",
    description="an example traffic situation generated using the maritime-schema python package",
    start_time=datetime.datetime.now(),
    own_ship=own_ship,
    target_ships=[],
    environment=None,
)

If we now want to save this traffic situation to a file, we simply call traffic_situation.model_dump_json(by_alias=True).

IMPORTANT: Always use by_alias=True when using model_dump_json, otherwise the output won't comply with the maritime-schema.

traffic_situation_json = traffic_situation.model_dump_json(by_alias=True, indent=4)

with open("traffic_situation.json", "w") as f:
    _ = f.write(traffic_situation_json)

Let's see the output:

{
    "title": "example situation",
    "description": "an example traffic situation generated using the python package maritime-schema",
    "startTime": "2024-04-03T14:13:21.756135",
    "ownShip": {
        "static": {
            "id": "14c94b5f-00ee-4c30-97c9-507862915076",
            "length": 200.0,
            "width": 30.0,
            "height": 10.0,
            "speedMax": 20.0,
            "mmsi": null,
            "imo": null,
            "name": "Starfish 2",
            "shipType": "Fishing"
        },
        "initial": {
            "position": {
                "latitude": 58.61,
                "longitude": 10.59
            },
            "sog": 10.0,
            "cog": 100.0,
            "heading": 200.0,
            "navStatus": "Under way using engine"
        },
        "waypoints": [
            {
                "position": {
                    "latitude": 58.61,
                    "longitude": 10.59
                },
                "turnRadius": null,
                "data": null
            },
            {
                "position": {
                    "latitude": 58.594299006647965,
                    "longitude": 10.759356798943921
                },
                "turnRadius": null,
                "data": null
            }
        ]
    },
    "targetShips": [],
    "environment": null
}

A valid scenario in JSON format has been created!

Creating an Output Schema File

Creating output schema files is similar to creating traffic situations, however, some additional classes are required.

Caga Configuration

Let's start by creating a caga configuration. Note: additional properties about the configuration can be added by adding extra keyword arguments.

from maritime_schema.types.caga import CagaConfiguration
caga_configuration = CagaConfiguration(name="CAGA System 1", vendor="VendorABC", version="1.2.3")

Route (Event Data)

Next we will create the route. A route is simply a list of waypoint objects. In this example, we are also adding speed data for each leg to the route.

The m_before_leg_change, m_after_leg_change, and interp_method can be set to none. These properties are only used if the route shall also contain information about how the ship speed changes between legs. In this example, we will assume instantaneous speed changes between legs.

from maritime_schema.types.caga import DataPoint, Data, Waypoint, Position

# Each route leg should have an associated speed.
wp1_sog_data = DataPoint(value=10, m_after_leg_change=0, m_before_leg_change=0, interp_method=None)
wp2_sog_data = DataPoint(value=10, m_after_leg_change=0, m_before_leg_change=0, interp_method=None)

# The sog data is added to a Data class.
wp1_data = Data(sog=wp1_sog_data)  # type: ignore
wp2_data = Data(sog=wp2_sog_data)  # type: ignore

# Create the individual waypoints.
wp1 = Waypoint(position=Position(latitude=1, longitude=1), turn_radius=100, data=wp1_data)
wp2 = Waypoint(position=Position(latitude=1.1, longitude=1.2), turn_radius=None, data=wp2_data)

new_route = [wp1, wp2]

With the route created, we can now add this to a CagaEvent. Then the CagaEvent can be added to CagaData.

CagaData contains all the caga-related data. This can include multiple CagaEvents (in cases where the proposed route by the system changes over time).

from maritime_schema.types.caga import CagaEvent, CagaData
import datetime

# create the event - a route was generated
event_1 = CagaEvent(time=datetime.datetime.now(), route=new_route, calculation_time=1.32)

# add the event to caga_data
caga_data = CagaData(configuration=caga_configuration, time_series_data=[], event_data=[event_1])

Time series data

In addition, it is also possible to add time series data to CagaData under the time_series_data section. This should be used if the system is collecting information (e.g. Target information) at a regular time interval. Let's add some time series data to our CagaData object in this example:

from uuid import uuid4
from maritime_schema.types.caga import DetectedShip, CagaTimeStep, AISNavStatus, EncounterType
detected_ship_1_t1 = DetectedShip(
    id=uuid4(),
    position=Position(latitude=1.23, longitude=1.24),
    sog=2.31,
    cog=11,
    heading=10,
    nav_status=AISNavStatus.ENGAGED_IN_FISHING,
    encounter_type=EncounterType.HEAD_ON,
    colreg_rules_applied=[],
    distance_to_target=1023.21,
    dcpa=100,
    tcpa=121,
    predictions=None,
)

detected_ship_1_t2 = DetectedShip(
    id=uuid4(),
    position=Position(latitude=1.231, longitude=1.242),
    sog=2.31,
    cog=11,
    heading=9,
    nav_status=AISNavStatus.ENGAGED_IN_FISHING,
    encounter_type=EncounterType.HEAD_ON,
    colreg_rules_applied=[],
    distance_to_target=1023.21,
    dcpa=100,
    tcpa=121,
    predictions=None,
)

time_step_0 = CagaTimeStep(time=datetime.datetime.now(), target_ships=[detected_ship_1_t1], internal_status={"cpu_temp": 55})
time_step_1 = CagaTimeStep(
    time=datetime.datetime.now() + datetime.timedelta(seconds=1),
    target_ships=[detected_ship_1_t2],
    internal_status={"cpu_temp": 57},
)

CagaData & Output Schema

Now that we have created both EventData and TimeSeriesData let's add them to CagaData. Then, we will create an OutputSchema. The process of saving the OutputSchema to a file is the same as for the TrafficSituation; using output_schema.model_dump_json(by_alias=True)

from maritime_schema.types.caga import CagaData
caga_data = CagaData(configuration=caga_configuration, time_series_data=[time_step_0, time_step_1], event_data=[event_1])

# include the original traffic situation in the output file, in this example, we will load it from a file
with open("traffic_situation.json", "r") as f:
    data = f.read()
traffic_situation = TrafficSituation.model_validate_json(data)

# create the output_schema
output_schema = OutputSchema(
    creation_time=datetime.datetime.now(),
    traffic_situation=traffic_situation,
    caga_data=caga_data,
    simulation_data=None,
)

# serialize the output_schema as a json string
output_schema_file_json = output_schema.model_dump_json(by_alias=True, indent=4)

# save the json string to a file
with open("output_schema_file.json", "w") as f:
    _ = f.write(output_schema_file_json)

Development Setup

1. Install Python 3.9 or higher, i.e. Python 3.10 or Python 3.11

2. Update pip and setuptools:

   python -m pip install --upgrade pip setuptools
   

3. git clone the maritime-schema repository into your local development directory:

   git clone https://github.com/dnv-opensource/maritime-schema path/to/your/dev/maritime-schema
   

4. In the maritime-schema root folder:

   Create a Python virtual environment:

   python -m venv .venv
   

   Activate the virtual environment:

   ..on Windows:

   > .venv\Scripts\activate.bat
   

   ..on Linux:

   source .venv/bin/activate
   

   Update pip and setuptools:

   (.venv) $ python -m pip install --upgrade pip setuptools
   

   Install maritime-schema's dependencies:

   (.venv) $ pip install -r requirements-dev.txt
   

   This should return without errors.

   Finally, install maritime-schema itself, yet not as a regular package but as an editable package instead, using the pip install option -e:

   (.venv) $ pip install -e .
   

5. Test that the installation works (in the maritime-schema root folder):

   (.venv) $ pytest .
   

Development Usage Example

Note: This section is only relevant if you plan to modify the maritime-schema!

API:

from maritime_schema.types import ...

CLI:

The JSON schemata are contained in the repository in folder ./schema If you did not clone the repository but installed the maritime-schema package as a dependency in your project you can call publish-schema on the command line to (re-)generate the schemata:

publish-schema

The publish-schema command will generate the JSON schemata in (current working directory)/schema
and a corresponding html documentation of the schemata in (current working directory)/docs/schema

For more examples and usage, please refer to maritime-schema's documentation.

Meta

Copyright (c) 2024 DNV AS. All rights reserved.

Minos Hemrich - minos.hemrich@dnv.com

Tom Arne Pedersen - tom.arne.pedersen@dnv.com

Claas Rostock - @LinkedIn - claas.rostock@dnv.com

Distributed under the MIT license. See LICENSE for more information.

https://github.com/dnv-opensource/maritime-schema

Contributing

1. Fork it (https://github.com/dnv-opensource/maritime-schema/fork)
2. Create your branch (git checkout -b my-branch-name)
3. Commit your changes (git commit -am 'place a descriptive commit message here')
4. Push to the branch (git push origin my-branch-name)
5. Create a new Pull Request in GitHub

For your contribution, please make sure you follow the STYLEGUIDE before creating the Pull Request.