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merged 5 commits into from
Jun 17, 2022
Merged

Add handling with extra precision in lat/long #80

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28b2d25
Add handling with extra precision in lat/long
gamblor21 Jun 13, 2022
d22cc67
Fix to handle other nmea data string lengths
gamblor21 Jun 14, 2022
4ccc6b9
Changed tests as internal representation of degrees changed
gamblor21 Jun 14, 2022
9f90c48
Refactor for mpy-cross
gamblor21 Jun 14, 2022
872ce6e
Spelling mistake, comment
gamblor21 Jun 16, 2022
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34 changes: 29 additions & 5 deletions adafruit_gps.py
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Original file line number Diff line number Diff line change
Expand Up @@ -80,10 +80,15 @@ def _parse_degrees(nmea_data):
# Where ddd is the degrees, mm.mmmm is the minutes.
if nmea_data is None or len(nmea_data) < 3:
return None
raw = float(nmea_data)
deg = raw // 100
minutes = raw % 100
return deg + minutes / 60
# To avoid losing precision handle degrees and minutes separately
# Return the final value as an integer. Further functions can parse
# this into a float or separate parts to retain the precision
raw = nmea_data.split(".")
degrees = int(raw[0]) // 100 * 1000000 # the ddd
minutes = int(raw[0]) % 100 # the mm.
minutes += int(f"{raw[1][:4]:0<4}") / 10000
minutes = int(minutes / 60 * 1000000)
return degrees + minutes # return parsed string in the format dddmmmmmm


def _parse_int(nmea_data):
Expand All @@ -105,12 +110,21 @@ def _parse_str(nmea_data):


def _read_degrees(data, index, neg):
x = data[index]
# This function loses precision with float32
x = data[index] / 1000000
if data[index + 1].lower() == neg:
x *= -1.0
return x


def _read_int_degrees(data, index, neg):
deg = data[index] // 1000000
minutes = data[index] % 1000000 / 10000
if data[index + 1].lower() == neg:
deg *= -1
return (deg, minutes)


def _parse_talker(data_type):
# Split the data_type into talker and sentence_type
if data_type[:1] == b"P": # Proprietary codes
Expand Down Expand Up @@ -208,7 +222,11 @@ def __init__(self, uart, debug=False):
# Initialize null starting values for GPS attributes.
self.timestamp_utc = None
self.latitude = None
self.latitude_degrees = None
self.latitude_minutes = None # Use for full precision minutes
self.longitude = None
self.longitude_degrees = None
self.longitude_minutes = None # Use for full precision minutes
self.fix_quality = 0
self.fix_quality_3d = 0
self.satellites = None
Expand Down Expand Up @@ -424,9 +442,11 @@ def _parse_gll(self, data):

# Latitude
self.latitude = _read_degrees(data, 0, "s")
self.latitude_degrees, self.latitude_minutes = _read_int_degrees(data, 0, "s")

# Longitude
self.longitude = _read_degrees(data, 2, "w")
self.longitude_degrees, self.longitude_minutes = _read_int_degrees(data, 2, "w")

# UTC time of position
self._update_timestamp_utc(data[4])
Expand Down Expand Up @@ -462,9 +482,11 @@ def _parse_rmc(self, data):

# Latitude
self.latitude = _read_degrees(data, 2, "s")
self.latitude_degrees, self.latitude_minutes = _read_int_degrees(data, 2, "s")

# Longitude
self.longitude = _read_degrees(data, 4, "w")
self.longitude_degrees, self.longitude_minutes = _read_int_degrees(data, 4, "w")

# Speed over ground, knots
self.speed_knots = data[6]
Expand Down Expand Up @@ -498,9 +520,11 @@ def _parse_gga(self, data):

# Latitude
self.latitude = _read_degrees(data, 1, "s")
self.latitude_degrees, self.latitude_minutes = _read_int_degrees(data, 1, "s")

# Longitude
self.longitude = _read_degrees(data, 3, "w")
self.longitude_degrees, self.longitude_minutes = _read_int_degrees(data, 3, "w")

# GPS quality indicator
# 0 - fix not available,
Expand Down
10 changes: 10 additions & 0 deletions examples/gps_simpletest.py
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,16 @@
)
print("Latitude: {0:.6f} degrees".format(gps.latitude))
print("Longitude: {0:.6f} degrees".format(gps.longitude))
print(
"Precise Latitude: {:2.}{:2.4f} degrees".format(
gps.latitude_degrees, gps.latitude_minutes
)
)
print(
"Precise Longitude: {:2.}{:2.4f} degrees".format(
gps.longitude_degrees, gps.longitude_minutes
)
)
print("Fix quality: {}".format(gps.fix_quality))
# Some attributes beyond latitude, longitude and timestamp are optional
# and might not be present. Check if they're None before trying to use!
Expand Down
14 changes: 7 additions & 7 deletions tests/adafruit_gps_test.py
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Expand Up @@ -21,9 +21,9 @@
@pytest.mark.parametrize(
("val", "exp"),
(
pytest.param("0023.456", 0.390933, id="leading zero"),
pytest.param("6413.9369", 64.23228, id="regular value"),
pytest.param("2747.416122087989", 27.79027, id="long value"),
pytest.param("0023.456", 390933, id="leading zero"),
pytest.param("6413.9369", 64232281, id="regular value"),
pytest.param("2747.416122087989", 27790268, id="long value"),
),
)
def test_parse_degrees(val, exp):
Expand Down Expand Up @@ -61,10 +61,10 @@ def test_parse_float_invalid(val):
@pytest.mark.parametrize(
("data", "neg", "exp"),
(
pytest.param([27.79027, "S"], "s", -27.79027, id="south negative"),
pytest.param([64.23228, "N"], "s", 64.23228, id="north not negative"),
pytest.param([123.4567, "W"], "w", -123.4567, id="west negative"),
pytest.param([10.7891, "E"], "w", 10.7891, id="east not negative"),
pytest.param([27790270, "S"], "s", -27.79027, id="south negative"),
pytest.param([64232280, "N"], "s", 64.23228, id="north not negative"),
pytest.param([123456700, "W"], "w", -123.4567, id="west negative"),
pytest.param([10789100, "E"], "w", 10.7891, id="east not negative"),
),
)
def test_read_degrees(data, neg, exp):
Expand Down