Added optionally distance calculation (fixes #86)

CHANGELOG.md

@@ -1,5 +1,6 @@
 # CHANGELOG
 ## not released
+- parser: Added optionally distance calculation (fixes #86)
 - parser: Added support for weather data from FANET ground stations
 - parser: Added support for latency in receiver messages (OGNSDR) (fixes #87)
 - parser: Added support for reference_timestamp with tzinfo (fixes #84)

ogn/parser/parse.py

@@ -1,7 +1,7 @@
 import re
 from datetime import datetime
 
-from ogn.parser.utils import createTimestamp, parseAngle, KNOTS_TO_MS, KPH_TO_MS, FEETS_TO_METER, fahrenheit_to_celsius
+from ogn.parser.utils import createTimestamp, parseAngle, KNOTS_TO_MS, KPH_TO_MS, FEETS_TO_METER, fahrenheit_to_celsius, CheapRuler
 from ogn.parser.pattern import PATTERN_APRS, PATTERN_APRS_POSITION, PATTERN_APRS_POSITION_WEATHER, PATTERN_APRS_STATUS, PATTERN_SERVER
 from ogn.parser.exceptions import AprsParseError
 
@@ -18,8 +18,12 @@ from ogn.parser.aprs_comment.spot_parser import SpotParser
 from ogn.parser.aprs_comment.inreach_parser import InreachParser
 from ogn.parser.aprs_comment.generic_parser import GenericParser
 
+positions = {}
+
+
+def parse(aprs_message, reference_timestamp=None, calculate_distances=False):
+    global positions
 
-def parse(aprs_message, reference_timestamp=None):
     if reference_timestamp is None:
         reference_timestamp = datetime.utcnow()
 
@@ -28,6 +32,13 @@ def parse(aprs_message, reference_timestamp=None):
         message.update(parse_comment(message['comment'],
                                      dstcall=message['dstcall'],
                                      aprs_type=message['aprs_type']))
+
+    if message['aprs_type'].startswith('position') and calculate_distances is True:
+        positions[message['name']] = (message['longitude'], message['latitude'])
+        if message['receiver_name'] in positions:
+            cheap_ruler = CheapRuler((message['latitude'] + positions[message['receiver_name']][1]) / 2.0)
+            message['distance'] = cheap_ruler.distance((message['longitude'], message['latitude']), positions[message['receiver_name']])
+
     return message
 
 

ogn/parser/utils.py

@@ -1,4 +1,5 @@
 from datetime import datetime, timedelta, timezone
+import math
 
 FEETS_TO_METER = 0.3048             # ratio feets to meter
 FPM_TO_MS = FEETS_TO_METER / 60     # ratio fpm to m/s
@@ -52,3 +53,24 @@ def createTimestamp(time_string, reference_timestamp):
             result += timedelta(days=1)
 
     return result
+
+
+class CheapRuler():
+    """Extreme fast distance calculating for distances below 500km."""
+
+    def __init__(self, lat):
+        c = math.cos(lat * 3.14159265359 / 180)
+        c2 = 2 * c * c - 1
+        c3 = 2 * c * c2 - c
+        c4 = 2 * c * c3 - c2
+        c5 = 2 * c * c4 - c3
+
+        self.kx = 1000 * (111.41513 * c - 0.09455 * c3 + 0.00012 * c5)  # longitude correction
+        self.ky = 1000 * (111.13209 - 0.56605 * c2 + 0.0012 * c4)       # latitude correction
+
+    def distance(self, a, b):
+        """Points a and b are from tuple(lon,lat)."""
+
+        dx = (a[0] - b[0]) * self.kx
+        dy = (a[1] - b[1]) * self.ky
+        return math.sqrt(dx * dx + dy * dy)

tests/parser/test_utils.py

@@ -1,7 +1,7 @@
 import unittest
 from datetime import datetime, timezone
 
-from ogn.parser.utils import parseAngle, createTimestamp
+from ogn.parser.utils import parseAngle, createTimestamp, CheapRuler
 
 
 class TestStringMethods(unittest.TestCase):
@@ -40,6 +40,14 @@ class TestStringMethods(unittest.TestCase):
 
         self.proceed_test_data(test_data)
 
+    def test_cheap_ruler(self):
+        koenigsdf = (11.465353, 47.829825)
+        hochkoenig = (13.062405, 47.420516)
+
+        cheap_ruler = CheapRuler((koenigsdf[1] + hochkoenig[1]) / 2)
+        distance = cheap_ruler.distance(koenigsdf, hochkoenig)
+        self.assertEqual(distance, 128381.47612138899)
+
 
 if __name__ == '__main__':
     unittest.main()