Re: [pysolar-discuss] Strange azimuth values

[Brandon Stafford <brandon@xxxxxxxxxxxxxxx>]

Hi Jay,

That's a beautiful pair of charts! Is that a PV tracker you're building or what?

One other question: what version of Pysolar are you needing to make
azimuth corrections with?

Brandon

On Mon, May 11, 2015 at 10:48 AM, Jay Doscher <jay@xxxxxxxxxxxxx> wrote:
> Looks like two curves to me, here's a graph of heading (corrected azimuth)
> and elevation of my project.  Negative solar altitude simply means the sun
> is below the horizon.
>
> On Mon, May 11, 2015 at 4:41 AM, Frank Lazzarini <flazzarini@xxxxxxxxx>
> wrote:
>>
>> When I apply the proposed method I get these results,
>>
>> [2015-05-10 00:00:00+00:25] Altitude: -22.817917957170042 Azimuth:
>> 0.9195853796406368
>> [2015-05-10 01:00:00+00:25] Altitude: -21.35437669913535 Azimuth:
>> 16.282490410169657
>> [2015-05-10 02:00:00+00:25] Altitude: -17.460113361911073 Azimuth:
>> 30.88264446553194
>> [2015-05-10 03:00:00+00:25] Altitude: -11.530293822218377 Azimuth:
>> 44.334853539473784
>> [2015-05-10 04:00:00+00:25] Altitude: -4.041985922217601 Azimuth:
>> 56.64229429837951
>> [2015-05-10 05:00:00+00:25] Altitude: 4.721075310609919 Azimuth:
>> 68.08448558243651
>> [2015-05-10 06:00:00+00:25] Altitude: 13.916416678430616 Azimuth:
>> 79.1019578849806
>> [2015-05-10 07:00:00+00:25] Altitude: 23.540263468364685 Azimuth:
>> 90.25884449955726
>> [2015-05-10 08:00:00+00:25] Altitude: 33.162952138663265 Azimuth:
>> 102.29127881328759
>> [2015-05-10 09:00:00+00:25] Altitude: 42.311459924908625 Azimuth:
>> 116.22795411782772
>> [2015-05-10 10:00:00+00:25] Altitude: 50.279286820496274 Azimuth:
>> 133.49311577994877
>> [2015-05-10 11:00:00+00:25] Altitude: 55.94436234658116 Azimuth:
>> 155.49523632286264
>> [2015-05-10 12:00:00+00:25] Altitude: 57.89747249155467 Azimuth:
>> 181.6026287381771
>> [2015-05-10 13:00:00+00:25] Altitude: 55.45948436540424 Azimuth:
>> 207.40278382169132
>> [2015-05-10 14:00:00+00:25] Altitude: 49.46294168127422 Azimuth:
>> 228.8272461199938
>> [2015-05-10 15:00:00+00:25] Altitude: 41.31880137304067 Azimuth:
>> 245.63086306581897
>> [2015-05-10 16:00:00+00:25] Altitude: 32.09659468953159 Azimuth:
>> 259.28835550065156
>> [2015-05-10 17:00:00+00:25] Altitude: 22.46665426651643 Azimuth:
>> 271.18090530087704
>> [2015-05-10 18:00:00+00:25] Altitude: 12.887187896956561 Azimuth:
>> 282.29565250233105
>> [2015-05-10 19:00:00+00:25] Altitude: 3.8032148272317357 Azimuth:
>> 293.34291810798067
>> [2015-05-10 20:00:00+00:25] Altitude: -4.854352153303335 Azimuth:
>> 304.8696257443884
>> [2015-05-10 21:00:00+00:25] Altitude: -12.152382809733522 Azimuth:
>> 317.2976741424302
>> [2015-05-10 22:00:00+00:25] Altitude: -17.83265833925366 Azimuth:
>> 330.87639859009437
>>
>> On Sun, May 10, 2015 at 11:28 PM, Jay Doscher <jay@xxxxxxxxxxxxx> wrote:
>>>
>>> I found the same issue, and managed to successfully offset it in my
>>> python code.  A disclaimer though- this works for me in the southwest US,
>>> and may be different elsewhere.
>>>
>>> def getsolarheading():
>>>         Azimuth = Pysolar.GetAzimuth(maplat, maplon,
>>> datetime.datetime.utcnow())
>>>         if Azimuth < 0:
>>>                 if (Azimuth >= -180):
>>>                         solarheading = ((Azimuth * -1) + 180)
>>>                 if (Azimuth < -180):
>>>                         solarheading = ((Azimuth * -1) - 180)
>>>         if Azimuth >= 0:
>>>                 solarheading = Azimuth
>>>         return solarheading
>>>
>>> This code will translate the Azimuth from Pysolar into a compass heading.
>>> I'm not sure what to tell you about altitude.
>>>
>>> Cheers,
>>> Jay
>>>
>>> On Sun, May 10, 2015 at 2:05 PM, Frank Lazzarini <flazzarini@xxxxxxxxx>
>>> wrote:
>>>>
>>>> Hi there,
>>>>
>>>> when I run the following simulation I get really odd azimuth values.
>>>> Well at least they seem odd, if I understood the documentation correctly
>>>> they from ~90 over 0 to -90 degrees. When I run a simulation of an entire
>>>> day I get really odd values for azimuth.
>>>>
>>>> from pysolar.solar import get_azimuth, get_altitude
>>>> from datetime import datetime
>>>> from pytz import timezone
>>>>
>>>>
>>>> latitude = 49.707524
>>>> longitude = 6.244362
>>>> year = 2015
>>>> month = 5
>>>> day = 10
>>>>
>>>>
>>>> def get_sun_position(latitude, longitude, time):
>>>>     alt = get_altitude(latitude, longitude, time)
>>>>     azi = get_azimuth(latitude, longitude, time)
>>>>     return alt, azi
>>>>
>>>> tzinfo = timezone('Europe/Luxembourg')
>>>> today = datetime.now(tz=tzinfo)
>>>>
>>>> for hour in range(0, 23):
>>>>     time = datetime(
>>>>         year,
>>>>         month,
>>>>         day,
>>>>         hour,
>>>>         0,
>>>>         tzinfo=tzinfo
>>>>     )
>>>>     alt, azi = get_sun_position(latitude, longitude, time)
>>>>     print("[{}] Altitude: {} Azimuth: {}".format(time, alt, azi))
>>>>
>>>>
>>>> Now when I run this I get the following values
>>>>
>>>>
>>>> [2015-05-10 00:00:00+00:25] Altitude: -22.817917957170042 Azimuth:
>>>> -180.91958537964064
>>>> [2015-05-10 01:00:00+00:25] Altitude: -21.35437669913535 Azimuth:
>>>> -196.28249041016966
>>>> [2015-05-10 02:00:00+00:25] Altitude: -17.460113361911073 Azimuth:
>>>> -210.88264446553194
>>>> [2015-05-10 03:00:00+00:25] Altitude: -11.530293822218377 Azimuth:
>>>> -224.33485353947378
>>>> [2015-05-10 04:00:00+00:25] Altitude: -4.041985922217601 Azimuth:
>>>> -236.6422942983795
>>>> [2015-05-10 05:00:00+00:25] Altitude: 4.721075310609919 Azimuth:
>>>> -248.0844855824365
>>>> [2015-05-10 06:00:00+00:25] Altitude: 13.916416678430616 Azimuth:
>>>> -259.1019578849806
>>>> [2015-05-10 07:00:00+00:25] Altitude: 23.540263468364685 Azimuth:
>>>> -270.25884449955726
>>>> [2015-05-10 08:00:00+00:25] Altitude: 33.162952138663265 Azimuth:
>>>> -282.2912788132876
>>>> [2015-05-10 09:00:00+00:25] Altitude: 42.311459924908625 Azimuth:
>>>> -296.2279541178277
>>>> [2015-05-10 10:00:00+00:25] Altitude: 50.279286820496274 Azimuth:
>>>> -313.49311577994877
>>>> [2015-05-10 11:00:00+00:25] Altitude: 55.94436234658116 Azimuth:
>>>> -335.49523632286264
>>>> [2015-05-10 12:00:00+00:25] Altitude: 57.89747249155467 Azimuth:
>>>> -1.6026287381770885
>>>> [2015-05-10 13:00:00+00:25] Altitude: 55.45948436540424 Azimuth:
>>>> -27.402783821691315
>>>> [2015-05-10 14:00:00+00:25] Altitude: 49.46294168127422 Azimuth:
>>>> -48.82724611999379
>>>> [2015-05-10 15:00:00+00:25] Altitude: 41.31880137304067 Azimuth:
>>>> -65.63086306581897
>>>> [2015-05-10 16:00:00+00:25] Altitude: 32.09659468953159 Azimuth:
>>>> -79.28835550065156
>>>> [2015-05-10 17:00:00+00:25] Altitude: 22.46665426651643 Azimuth:
>>>> -91.18090530087704
>>>> [2015-05-10 18:00:00+00:25] Altitude: 12.887187896956561 Azimuth:
>>>> -102.29565250233105
>>>> [2015-05-10 19:00:00+00:25] Altitude: 3.8032148272317357 Azimuth:
>>>> -113.34291810798067
>>>> [2015-05-10 20:00:00+00:25] Altitude: -4.854352153303335 Azimuth:
>>>> -124.86962574438837
>>>> [2015-05-10 21:00:00+00:25] Altitude: -12.152382809733522 Azimuth:
>>>> -137.2976741424302
>>>> [2015-05-10 22:00:00+00:25] Altitude: -17.83265833925366 Azimuth:
>>>> -150.87639859009437
>>>>
>>>>
>>>>
>>>> Any ideas?
>>>>
>>>> --
>>>>
>>>> Frank Lazzarini
>>>> Email: flazzarini@xxxxxxxxx  Phone: +352 621 314 430
>>>> Blog:   http://www.gefoo.org   LinkedIn:
>>>> http://www.linkedin.com/pub/frank-lazzarini/1a/a30/112
>>>>
>>>
>>
>>
>>
>> --
>>
>> Frank Lazzarini
>> Email: flazzarini@xxxxxxxxx  Phone: +352 621 314 430
>> Blog:   http://www.gefoo.org   LinkedIn:
>> http://www.linkedin.com/pub/frank-lazzarini/1a/a30/112
>>
>



-- 
Brandon Stafford
Rascal Micro: small computers for art and science
Somerville, MA, USA
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