A 100% python weather routing library for sailing.
Read the LICENSE file.
This work is partially based and inspired by Riccardo Apolloni Virtual Sailing Simulator.
pip install git+https://github.com/dakk/libweatherrouting.git
For a comprehensive usage reference example pleace refer to wind_forecast_routing QGIS plugin or GWeatherRouting standalone application
Almost one external function has to be implemented as a preliminary requirement for library usage:
A function that accept a datetime item, a float latitude and float longitude as parameters,
performs a wind forecast analysis for the specified time and location (usually sampling a grib file)
and returns a tuple with true wind direction (twd
) expressed in radians and true wind speed (tws
) expressed in meters per second or None
if running out of temporal/geographic grib scope.
def getWindAt( t, lat, lon)
# wind forecast analysys implementation
...
return (twd, tws)
A function that accept a float latitude and float longitude as parameters, performs a test to check if the specified location is eligible as waypoint (i.e. lay or not on sea) and returns a boolean (True if valid, False if invalid)
def point_validity(lat, lon)
#
...
return True/False
A function that accept a vector defined as four float parameters (latitude1, longitude1, latitude2, longitude2) performs a test to check whether the specified line between two waypoints is valid (i.e. lays completely or not on sea, or in other words is in line of sight) and returns a boolean (True if valid, False if invalid)
def line_validity(lat1, lon1, lat1, lon1)
#
...
return True/False
from weatherrouting import Routing, Polar
from weatherrouting.routers.linearbestisorouter import LinearBestIsoRouter
from datetime import datetime
Define a list of trackpoints as lat,long tuples (almost 2) that have to be reached by the route
track = ((5.1, 38.1), (5.2, 38.4), (5.7, 38.2))
Define the polar object from a polar file describing the performance of the boat at different wind speeds (tws
) and different angles (twd
)
polar_obj = Polar("polar_files/bavaria38.pol")
Define the polar object from a polar file describing the performance of the boat at different wind speeds (tws
) and different angles (`twd~)
start = datetime.fromisoformat('2021-04-02T12:00:00')
routing_obj = Routing(
LinearBestIsoRouter, # specify a router type
polar_obj, # the polar object for a specific sail boat
track, # the list of track points (lat,lon)
getWindAt, # the function that returns (twd,tws) for a specified (datetime, lat, lon)
start, # the start datetime
start_position = (4.8,37.8) # the start location (lat lon, optional, the first track point if undefined)
pointValidity = point_validity # the point validity function (optional)
lineValidity = line_validity # the line validity function (optional)
)
Calculate subsequent steps until the end track point is reached
while not self.routing_obj.end:
res = self.routing_obj.step()
the step method returns a RoutingResult object with the following informations during routing calculation:
res.time # the datetime of step
res.isochrones # all points reached at a specified datetime
res.progress # the calculation progress
and after the end of the routing calculation contains a list of tuple containing the waypoints informations (lat,lon,datetime, twd, tws, speed, heading)
res.path # the list of route waypoints
The path could be exported as a geojson object for cartographic representation
from weatherrouting.utils import pathAsGeojson
import json
json.dumps(pathAsGeojson(res.path))