Lookup altitude2

pvlib/location.py

@@ -4,7 +4,7 @@
 
 # Will Holmgren, University of Arizona, 2014-2016.
 
-import os
+import pathlib
 import datetime
 import warnings
 
@@ -45,8 +45,10 @@ class Location:
         pytz.timezone objects will be converted to strings.
         ints and floats must be in hours from UTC.
 
-    altitude : float, default 0.
+    altitude : None or float, default None
         Altitude from sea level in meters.
+        If None, the altitude will be fetched from
+        :py:func:`pvlib.location.lookup_altitude`.
 
     name : None or string, default None.
         Sets the name attribute of the Location object.
@@ -56,7 +58,8 @@ class Location:
     pvlib.pvsystem.PVSystem
     """
 
-    def __init__(self, latitude, longitude, tz='UTC', altitude=0, name=None):
+    def __init__(self, latitude, longitude, tz='UTC', altitude=None,
+                 name=None):
 
         self.latitude = latitude
         self.longitude = longitude
@@ -76,6 +79,9 @@ def __init__(self, latitude, longitude, tz='UTC', altitude=0, name=None):
         else:
             raise TypeError('Invalid tz specification')
 
+        if altitude is None:
+            altitude = lookup_altitude(latitude, longitude)
+
         self.altitude = altitude
 
         self.name = name
@@ -427,8 +433,8 @@ def lookup_altitude(latitude, longitude):
 
     """
 
-    pvlib_path = os.path.dirname(os.path.abspath(__file__))
-    filepath = os.path.join(pvlib_path, 'data', 'Altitude.h5')
+    pvlib_path = pathlib.Path(__file__).parent
+    filepath = pvlib_path / 'data' / 'Altitude.h5'
 
     latitude_index = _degrees_to_index(latitude, coordinate='latitude')
     longitude_index = _degrees_to_index(longitude, coordinate='longitude')

pvlib/solarposition.py

@@ -24,7 +24,7 @@
 import warnings
 import datetime
 
-from pvlib import atmosphere
+from pvlib import atmosphere, location
 from pvlib.tools import datetime_to_djd, djd_to_datetime
 
 
@@ -52,12 +52,13 @@ def get_solarposition(time, latitude, longitude,
         negative to west.
 
     altitude : None or float, default None
-        If None, computed from pressure. Assumed to be 0 m
-        if pressure is also None.
+        Altitude from sea level in meters.
+        If None, the altitude will be fetched from
+        :py:func:`pvlib.location.lookup_altitude`.
 
     pressure : None or float, default None
-        If None, computed from altitude. Assumed to be 101325 Pa
-        if altitude is also None.
+        Air pressure in Pascals.
+        If None, computed from altitude.
 
     method : string, default 'nrel_numpy'
         'nrel_numpy' uses an implementation of the NREL SPA algorithm
@@ -92,12 +93,10 @@ def get_solarposition(time, latitude, longitude,
     .. [3] NREL SPA code: http://rredc.nrel.gov/solar/codesandalgorithms/spa/
     """
 
-    if altitude is None and pressure is None:
-        altitude = 0.
-        pressure = 101325.
-    elif altitude is None:
-        altitude = atmosphere.pres2alt(pressure)
-    elif pressure is None:
+    if altitude is None:
+        altitude = location.lookup_altitude(latitude, longitude)
+
+    if pressure is None:
         pressure = atmosphere.alt2pres(altitude)
 
     method = method.lower()
@@ -129,7 +128,7 @@ def get_solarposition(time, latitude, longitude,
     return ephem_df
 
 
-def spa_c(time, latitude, longitude, pressure=101325, altitude=0,
+def spa_c(time, latitude, longitude, pressure=None, altitude=None,
           temperature=12, delta_t=67.0,
           raw_spa_output=False):
     """
@@ -153,10 +152,13 @@ def spa_c(time, latitude, longitude, pressure=101325, altitude=0,
     longitude : float
         Longitude in decimal degrees. Positive east of prime meridian,
         negative to west.
-    pressure : float, default 101325
-        Pressure in Pascals
-    altitude : float, default 0
-        Height above sea level. [m]
+    pressure : None or float, default None
+        Air pressure in Pascals.
+        If None, computed from altitude.
+    altitude : None or float, default None
+        Altitude from sea level in meters.
+        If None, the altitude will be fetched from
+        :py:func:`pvlib.location.lookup_altitude`.
     temperature : float, default 12
         Temperature in C
     delta_t : float, default 67.0
@@ -194,6 +196,11 @@ def spa_c(time, latitude, longitude, pressure=101325, altitude=0,
     pyephem, spa_python, ephemeris
     """
 
+    if altitude is None:
+        altitude = location.lookup_altitude(latitude, longitude)
+    if pressure is None:
+        pressure = atmosphere.alt2pres(altitude)
+
     # Added by Rob Andrews (@Calama-Consulting), Calama Consulting, 2014
     # Edited by Will Holmgren (@wholmgren), University of Arizona, 2014
     # Edited by Tony Lorenzo (@alorenzo175), University of Arizona, 2015
@@ -275,7 +282,7 @@ def _spa_python_import(how):
 
 
 def spa_python(time, latitude, longitude,
-               altitude=0, pressure=101325, temperature=12, delta_t=67.0,
+               altitude=None, pressure=None, temperature=12, delta_t=67.0,
                atmos_refract=None, how='numpy', numthreads=4):
     """
     Calculate the solar position using a python implementation of the
@@ -298,10 +305,13 @@ def spa_python(time, latitude, longitude,
     longitude : float
         Longitude in decimal degrees. Positive east of prime meridian,
         negative to west.
-    altitude : float, default 0
-        Distance above sea level.
-    pressure : int or float, optional, default 101325
+    altitude : None or float, default None
+        Altitude from sea level in meters.
+        If None, the altitude will be fetched from
+        :py:func:`pvlib.location.lookup_altitude`.
+    pressure : int or float, optional, default None
         avg. yearly air pressure in Pascals.
+        If None, computed from altitude.
     temperature : int or float, optional, default 12
         avg. yearly air temperature in degrees C.
     delta_t : float, optional, default 67.0
@@ -351,6 +361,11 @@ def spa_python(time, latitude, longitude,
     pyephem, spa_c, ephemeris
     """
 
+    if altitude is None:
+        altitude = location.lookup_altitude(latitude, longitude)
+    if pressure is None:
+        pressure = atmosphere.alt2pres(altitude)
+
     # Added by Tony Lorenzo (@alorenzo175), University of Arizona, 2015
 
     lat = latitude
@@ -504,8 +519,8 @@ def _ephem_setup(latitude, longitude, altitude, pressure, temperature,
 
 def sun_rise_set_transit_ephem(times, latitude, longitude,
                                next_or_previous='next',
-                               altitude=0,
-                               pressure=101325,
+                               altitude=None,
+                               pressure=None,
                                temperature=12, horizon='0:00'):
     """
     Calculate the next sunrise and sunset times using the PyEphem package.
@@ -520,10 +535,13 @@ def sun_rise_set_transit_ephem(times, latitude, longitude,
         Longitude in degrees, positive east of prime meridian, negative to west
     next_or_previous : str
         'next' or 'previous' sunrise and sunset relative to time
-    altitude : float, default 0
-        distance above sea level in meters.
-    pressure : int or float, optional, default 101325
-        air pressure in Pascals.
+    altitude : None or float, default None
+        Altitude from sea level in meters.
+        If None, the altitude will be fetched from
+        :py:func:`pvlib.location.lookup_altitude`.
+    pressure : None or float, default None
+        Air pressure in Pascals.
+        If None, computed from altitude.
     temperature : int or float, optional, default 12
         air temperature in degrees C.
     horizon : string, format +/-X:YY
@@ -555,6 +573,11 @@ def sun_rise_set_transit_ephem(times, latitude, longitude,
     else:
         raise ValueError('times must be localized')
 
+    if altitude is None:
+        altitude = location.lookup_altitude(latitude, longitude)
+    if pressure is None:
+        pressure = atmosphere.alt2pres(altitude)
+
     obs, sun = _ephem_setup(latitude, longitude, altitude,
                             pressure, temperature, horizon)
     # create lists of sunrise and sunset time localized to time.tz
@@ -588,7 +611,7 @@ def sun_rise_set_transit_ephem(times, latitude, longitude,
                                            'transit': trans})
 
 
-def pyephem(time, latitude, longitude, altitude=0, pressure=101325,
+def pyephem(time, latitude, longitude, altitude=None, pressure=None,
             temperature=12, horizon='+0:00'):
     """
     Calculate the solar position using the PyEphem package.
@@ -603,10 +626,13 @@ def pyephem(time, latitude, longitude, altitude=0, pressure=101325,
     longitude : float
         Longitude in decimal degrees. Positive east of prime meridian,
         negative to west.
-    altitude : float, default 0
-        Height above sea level in meters. [m]
-    pressure : int or float, optional, default 101325
-        air pressure in Pascals.
+    altitude : None or float, default None
+        Altitude from sea level in meters.
+        If None, the altitude will be fetched from
+        :py:func:`pvlib.location.lookup_altitude`.
+    pressure : None or float, default None
+        Air pressure in Pascals.
+        If None, computed from altitude.
     temperature : int or float, optional, default 12
         air temperature in degrees C.
     horizon : string, optional, default '+0:00'
@@ -642,6 +668,11 @@ def pyephem(time, latitude, longitude, altitude=0, pressure=101325,
     except TypeError:
         time_utc = time
 
+    if altitude is None:
+        altitude = location.lookup_altitude(latitude, longitude)
+    if pressure is None:
+        pressure = atmosphere.alt2pres(altitude)
+
     sun_coords = pd.DataFrame(index=time)
 
     obs, sun = _ephem_setup(latitude, longitude, altitude,
@@ -862,7 +893,7 @@ def ephemeris(time, latitude, longitude, pressure=101325, temperature=12):
 
 
 def calc_time(lower_bound, upper_bound, latitude, longitude, attribute, value,
-              altitude=0, pressure=101325, temperature=12, horizon='+0:00',
+              altitude=None, pressure=None, temperature=12, horizon='+0:00',
               xtol=1.0e-12):
     """
     Calculate the time between lower_bound and upper_bound
@@ -885,11 +916,14 @@ def calc_time(lower_bound, upper_bound, latitude, longitude, attribute, value,
         and 'az' (which must be given in radians).
     value : int or float
         The value of the attribute to solve for
-    altitude : float, default 0
-        Distance above sea level.
-    pressure : int or float, optional, default 101325
+    altitude : None or float, default None
+        Altitude from sea level in meters.
+        If None, the altitude will be fetched from
+        :py:func:`pvlib.location.lookup_altitude`.
+    pressure : int or float, optional, default None
         Air pressure in Pascals. Set to 0 for no
         atmospheric correction.
+        If None, computed from altitude.
     temperature : int or float, optional, default 12
         Air temperature in degrees C.
     horizon : string, optional, default '+0:00'
@@ -913,6 +947,12 @@ def calc_time(lower_bound, upper_bound, latitude, longitude, attribute, value,
         If the given attribute is not an attribute of a
         PyEphem.Sun object.
     """
+
+    if altitude is None:
+        altitude = location.lookup_altitude(latitude, longitude)
+    if pressure is None:
+        pressure = atmosphere.alt2pres(altitude)
+
     obs, sun = _ephem_setup(latitude, longitude, altitude,
                             pressure, temperature, horizon)
 

pvlib/tests/test_location.py

@@ -12,6 +12,7 @@
 from pytz.exceptions import UnknownTimeZoneError
 
 import pvlib
+from pvlib import location
 from pvlib.location import Location, lookup_altitude
 from pvlib.solarposition import declination_spencer71
 from pvlib.solarposition import equation_of_time_spencer71
@@ -328,21 +329,28 @@ def test_extra_kwargs():
         Location(32.2, -111, arbitrary_kwarg='value')
 
 
-def test_lookup_altitude():
-    max_alt_error = 125
-    # location name, latitude, longitude, altitude
-    test_locations = [
-        ('Tucson, USA', 32.2540, -110.9742, 724),
-        ('Lusaka, Zambia', -15.3875, 28.3228, 1253),
-        ('Tokio, Japan', 35.6762, 139.6503, 40),
-        ('Canberra, Australia', -35.2802, 149.1310, 566),
-        ('Bogota, Colombia', 4.7110, -74.0721, 2555),
-        ('Dead Sea, West Bank', 31.525849, 35.449214, -415),
-        ('New Delhi, India', 28.6139, 77.2090, 214),
-        ('Null Island,  Atlantic Ocean', 0, 0, 0),
-    ]
-
-    for name, lat, lon, expected_alt in test_locations:
-        alt_found = lookup_altitude(lat, lon)
-        assert abs(alt_found - expected_alt) < max_alt_error, \
-            f'Max error exceded for {name} - e: {expected_alt} f: {alt_found}'
+@pytest.mark.parametrize('lat,lon,expected_alt', [
+    pytest.param(32.2540, -110.9742, 724, id='Tucson, USA'),
+    pytest.param(-15.3875, 28.3228, 1253, id='Lusaka, Zambia'),
+    pytest.param(35.6762, 139.6503, 40, id='Tokyo, Japan'),
+    pytest.param(-35.2802, 149.1310, 566, id='Canberra, Australia'),
+    pytest.param(4.7110, -74.0721, 2555, id='Bogota, Colombia'),
+    pytest.param(31.525849, 35.449214, -415, id='Dead Sea, West Bank'),
+    pytest.param(28.6139, 77.2090, 214, id='New Delhi, India'),
+    pytest.param(0, 0, 0, id='Null Island,  Atlantic Ocean'),
+])
+def test_lookup_altitude(lat, lon, expected_alt):
+    alt_found = lookup_altitude(lat, lon)
+    assert alt_found == pytest.approx(expected_alt, abs=125)
+
+
+def test_location_lookup_altitude(mocker):
+    mocker.spy(location, 'lookup_altitude')
+    tus = Location(32.2, -111, 'US/Arizona', 700, 'Tucson')
+    location.lookup_altitude.assert_not_called()
+    assert tus.altitude == 700
+    location.lookup_altitude.reset_mock()
+
+    tus = Location(32.2, -111, 'US/Arizona')
+    location.lookup_altitude.assert_called_once_with(32.2, -111)
+    assert tus.altitude == location.lookup_altitude(32.2, -111)

pvlib/tests/test_pvsystem.py

@@ -1678,7 +1678,7 @@ def test_PVSystem_multiple_array_get_aoi():
 def solar_pos():
     times = pd.date_range(start='20160101 1200-0700',
                           end='20160101 1800-0700', freq='6H')
-    location = Location(latitude=32, longitude=-111)
+    location = Location(latitude=32, longitude=-111, altitude=0)
     return location.get_solarposition(times)