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fixed sign of utc-gps time offset #1179

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b792920
fixed sign of utc-gps time offset
willat343 Nov 17, 2025
107dbe1
minor tweaks to ensure integer arithmetic
willat343 Nov 17, 2025
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10 changes: 5 additions & 5 deletions box_utils/box_auto/python/box_auto/scripts/cpt7/export_raw_imu_bag.py
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Original file line number Diff line number Diff line change
Expand Up @@ -38,10 +38,10 @@ def __init__(self, output_imu_msg_name):
self.times = None
self.expected_utc_offset = -18.0 # UTC time = GPS System Time + UTC offset
self.expected_gps_offset = 0.0
self.weeks_to_seconds = 604_800.0
self.weeks_to_seconds = 604_800
posix_start_in_utc = datetime(year=1970, month=1, day=1, hour=0, minute=0, second=0)
gps_start_in_utc = datetime(year=1980, month=1, day=6, hour=0, minute=0, second=0)
self.gps_epoch_start_in_POSIX_seconds = (gps_start_in_utc - posix_start_in_utc).total_seconds()
self.gps_epoch_start_in_POSIX_seconds = int((gps_start_in_utc - posix_start_in_utc).total_seconds())
self.x_accel = list()
self.minusy_accel = list()
self.z_accel = list()
Expand Down Expand Up @@ -83,15 +83,15 @@ def load_imu_times(self, imu_df: pd.DataFrame):
else:
self.logger.debug(f"IMU field name {imu_df.iloc[0, 0]} is correct {ColorLogger.GREEN_CHECK}")
WEEK_INDEX = 4
SOW_INDEX = 5 # Seconds of week
week = imu_df.iloc[:, WEEK_INDEX]
week = imu_df.iloc[:, WEEK_INDEX].astype(int)
SOW_INDEX = 5
seconds_of_week = imu_df.iloc[:, SOW_INDEX] - self.expected_gps_offset + self.expected_utc_offset
ns_of_seconds_of_week = [int(round(int(math.modf(x)[0] * 1e9) / 1000, 0)) * 1000 for x in seconds_of_week]
seconds_of_week_without_ns = seconds_of_week.astype(int)
seconds_since_gps_start_in_utc = week * self.weeks_to_seconds + seconds_of_week_without_ns
seconds_unix = seconds_since_gps_start_in_utc + self.gps_epoch_start_in_POSIX_seconds
self.logger.info(f"Log time starts at {datetime.utcfromtimestamp(seconds_unix[0])}")
self.ros_times = [rospy.Time(secs=int(x), nsecs=y) for x, y in zip(seconds_unix, ns_of_seconds_of_week)]
self.ros_times = [rospy.Time(secs=x, nsecs=y) for x, y in zip(seconds_unix, ns_of_seconds_of_week)]

def load_imu_data(self, imu_df: pd.DataFrame):
"""
Expand Down
4 changes: 2 additions & 2 deletions box_utils/boxi/boxi/set_cpt7_time.py
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ def set_internet_time():
gps_epoch_start = datetime.datetime(1980, 1, 6, 0, 0, 0)

print(response.tx_time)
delta_seconds = response.tx_time - datetime.datetime.timestamp(gps_epoch_start) - 18 - 3600
delta_seconds = response.tx_time - datetime.datetime.timestamp(gps_epoch_start) + 18 - 3600
gps_weeks = int(delta_seconds / 604800) # 604800 seconds in a GPS week
gps_seconds = delta_seconds % 604800 # 18 leap seconds since 1980
return gps_weeks, gps_seconds
Expand All @@ -38,7 +38,7 @@ def set_local_pc_time():
# Calculate the current GPS week and seconds since the start of GPS epoch (January 6, 1980 00:00:00 UTC)
gps_epoch_start = datetime.datetime(1980, 1, 6, 0, 0, 0)

delta_seconds = now - datetime.datetime.timestamp(gps_epoch_start) - 18 - 3600
delta_seconds = now - datetime.datetime.timestamp(gps_epoch_start) + 18 - 3600
gps_weeks = int(delta_seconds / 604800) # 604800 seconds in a GPS week
gps_seconds = delta_seconds % 604800 # 18 leap seconds since 1980
return gps_weeks, gps_seconds
Expand Down