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Handle NavSatFix NaN value to prevent crashes #63

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Handle NavSatFix NaN value to prevent crashes #63

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20 changes: 15 additions & 5 deletions scripts/ntrip_ros_base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
import json
import datetime
import importlib.util
from math import isnan

import rclpy
from rclpy.node import Node
Expand Down Expand Up @@ -129,17 +130,21 @@ def subscribe_fix(self, fix: NavSatFix):
millisecond = int(time.microsecond * 1e-4)
nmea_utc = f"{hour:02}{minute:02}{second:02}.{millisecond:02}"

# Handle NaN
latitude_nan = True if isnan(fix.latitude) else False
longitude_nan = True if isnan(fix.longitude) else False

# Figure out the direction of the latitude and longitude
nmea_lat_direction = "N"
nmea_lon_direction = "E"
if fix.latitude < 0:
if latitude_nan is False and fix.latitude < 0:
nmea_lat_direction = "S"
if fix.longitude < 0:
if longitude_nan is False and fix.longitude < 0:
nmea_lon_direction = "W"

# Convert the units of the latitude and longitude
nmea_lat = NMEAParser.lat_dd_to_dmm(fix.latitude)
nmea_lon = NMEAParser.lon_dd_to_dmm(fix.longitude)
nmea_lat = NMEAParser.lat_dd_to_dmm(fix.latitude) if latitude_nan is False else 0
nmea_lon = NMEAParser.lon_dd_to_dmm(fix.longitude) if longitude_nan is False else 0

# Convert the GPS quality to the right format for the sentence
status = fix.status.status
Expand All @@ -153,7 +158,12 @@ def subscribe_fix(self, fix: NavSatFix):
nmea_status = 0

# Assemble the sentence
nmea_sentence_no_checksum = f"$GPGGA,{nmea_utc},{nmea_lat},{nmea_lat_direction},{nmea_lon},{nmea_lon_direction},{nmea_status},05,1.0,100.0,M,-32.0,M,,0000"
nmea_sentence_no_checksum = (
f"$GPGGA,{nmea_utc},"
+ (f"{nmea_lat},{nmea_lat_direction}," if latitude_nan is False else ",,")
+ (f"{nmea_lon},{nmea_lon_direction}," if longitude_nan is False else ",,")
+ f"{nmea_status},05,1.0,100.0,M,-32.0,M,,0000"
)
nmea_checksum = NMEAParser.checksum(nmea_sentence_no_checksum)
nmea_sentence = f"{nmea_sentence_no_checksum}*{nmea_checksum:x}\r\n"

Expand Down