Instructions:
What the Program Does -
SunPosition computes the position of the sun and related information for a given location,
for multiple times and
days during the year. The output of the program is an array of this data, which you can
copy from your web
browser and paste into spreadsheet and other analytical applications. This information may
be useful in building
design, solar energy system design, photography, and other applications.
How it Differs from SunAngle-
SunAngle, which this program is based on, calculates solar data for a single day and time,
while SunPosition
calculates values for different days and times throughout the year. SunAngle has a few
more features and runs
much quicker, but it can't produce arrays of data.
How to Use the Program -
The basic procedure for using SunPosition is entering input information in the
"Inputs" section, clicking on the
"Calculate" button, waiting for the results to appear in the "Outputs"
box, selecting the output data.
Inputs-
The inputs are actually quite simple, and the only reason there are so many options on the
screen is to help you get exactly what data you're looking for in a format that is useful
to you.
Here is a list of inputs and how to use them:
Sun Angles
Select which output data you would like to produce. Those angles and other data
that are "checked"
will appear in the outputs, and others will not. By default, the "altitude" and
"azimuth" options are
checked.
Location
Your latitude, in degrees North or South of the equator (use the selector after
the text field to indicate
which one). Use decimal notation for latitude (degree-minute-second format doesn't work,
so
convert to decimal...for instance, a latitude of 40?0'00" would have decimal
equivalent of 40.5
degrees).
Data Resolution
Using the "Frequency" pull-down menu, you can choose to generate data
for every day of the year,
weekly, monthly, quarterly, or for only one day. For each day you've selected, the
"Resolution" menu
lets you determine how many samples you'd like, from once every 15 minutes to once a day.
The
"Start Date" is the first date you'll calculate data for, and as long as you're
calculating data for more
than one day this represents the beginning of the "year" for which you'll
produce data. The "Time"
input is used only if you selected "Once per day" as your data frequency in the
"Frequency" menu.
Note that the "Frequency" and "Resolution" inputs determine how many
samples you generate...a
frequency of "monthly" with a resolution of "every four hours" will
generate (12 days * 6 samples per
day) = 72 total samples.
Output Format
These input menus determine the presentation of the data in the "Outputs"
section...they do not affect
the calculations in any way. The "Delimiter" menu gives you options for the
characters used to
separate data in each line of the output. If you'd like to import the data into a
spreadsheet, you
probably want to select "tab" from this menu, which is the delimiter recognized
by most spreadsheets
for data importing. The "Angle Units" menu allows you to select degree or radian
angle units. The
"Date Style" and "Time Style" represent different ways of representing
the date and time labels, which
are present at the beginning of every line of output. Check the "Leap Year" box
if you're producing
data for a specific year that's a leap year.
Starting the Calculation
When you've entered all of the inputs, click on the "Calculate" button, and the
results will appear in the "Outputs"
box. Depending on the frequency and resolution of the data you selected, it may be
instaneous, or it may take
several seconds.
Outputs
The "Outputs" box will contain a one line SunPostion title, the latitude of your
location, a reminder of the angle
units, data headers, and the data, with one line per sample.