Source code for stonesoup.reader.aishub

import json
from datetime import datetime

import numpy as np

from .base import DetectionReader
from .file import TextFileReader
from ..types.detection import Detection
from stonesoup.buffered_generator import BufferedGenerator

[docs]class JSON_AISDetectionReader(DetectionReader, TextFileReader): """A simple detection reader for JSON files of AIS (maritime transponder) detections. This particular JSON AIS reader is written to read the JSON format used by files downloaded from '' (must be a contributor to their AIS database to download their files). JSON format:: [{"ERROR": "false"}, [{"NAME": "MARTCILINO", "MMSI": 205466990, "LONGITUDE": 3078401, "TIME": "1516233686", "LATITUDE": 31215032, ...}, {"NAME": "MARTCILINO", "MMSI": 205466990, "LONGITUDE": 3064592, "TIME": "1516234275", "LATITUDE": 31227463, ...}]] Notes ----- * TIME is in Linux Epoch format * LONGITUDE and LATITUDE are (long/lat degrees)*(600,000) * MMSI is unique ship identifier * The AIS detection attributes for lattitude, longitude, and timestamp are saved as the attributes of a 'Detection'; the other attributes are saved as the dictionary 'metadata' attribute of a 'Detection'. """ # path - inherited from 'TextFileReader'->'FileReader' def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs)
[docs] @BufferedGenerator.generator_method def detections_gen(self): # read data from the JSON file with as json_file: file_data = json.load(json_file) file_data = file_data[1] # sort the imported AIS Detection list by time of detection file_data.sort(key=lambda x: x['TIME']) for record in file_data: # extract latitude and longitude values from JSON record lat_value = float(record['LATITUDE'])/600000 lon_value = float(record['LONGITUDE'])/600000 # extract timestamp values from JSON record time_value = datetime.utcfromtimestamp(float( record['TIME'])) # delete lat, lon, timestamp from JSON record; # the rest is metadata del record['LATITUDE'] del record['LONGITUDE'] del record['TIME'] # form Detection object from JSON record detect = Detection( np.array([[lon_value], [lat_value]], dtype=np.float32), time_value, metadata=record) yield time_value, {detect}