UO Solar Radiation Monitoring Laboratory

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Sundial program

This program creates charts showing the direction and length of a shadow cast by the top of a pole (gnomon) of a given height upon a rectangular area, typically a roof or a field. The shadow cast by a pole can be drawn on the diagram by connecting a line from the pole's location (0, 0) to the end of the shadow at the time of interest. Shading of a PV array, by a pole or object causing the shading, can be seen by drawing the location of the array on the diagram relative to the pole. By default, dates are spaced about 30 days apart from one solstice to the next. The width and length of the plotted area can be specified and there are a several options available to allow you to alter the chart's appearance.
Resulting charts are displayed in your Web browser window, and they are formatted for printing. Two file formats are currently available: PDF (Adobe), and PNG, an international standard.
Please note that some charts, especially those for Arctic or Antarctic latitudes and those where the gnomon height is very short in relation to the dimensions of the chart, may have labels crowded together or otherwise display unexpected properties. Be sure to experiment with various sizing and display options.

Step 1—Specify location

  Use these values:
        Latitude (decimal degrees)
        Longitude (decimal degrees)
    [Important: south latitude and west longitude are given in negative degrees. Minutes and seconds must be converted to decimal degrees; e.g., 30 min. = 0.5 deg.]
  Look up location with:
        US 5-digit ZIP code

Step 2—Specify time zone

  Time zone

Step 3—Choose data to be plotted

  Plot dates 30 or 31 days apart, between solstices, December through June
  Plot dates 30 or 31 days apart, between solstices, June through December
  Plot dates having average solar radiation for December through June
  Plot dates having average solar radiation for June through December
  Plot only this date (YYYY-MM-DD):
  Plot hours in local solar time
  Plot hours in local standard time
  Show hours in international style
  Show hours in am/pm style
  Do not label hour curves

Step 4—Specify sun dial dimensions.

        Length
        Width above gnomon base
        Width below gnomon base
        Gnomon height
        Dimension units

Step 5—Set chart format parameters

  Color date curves
  Set style of date curves to
  Make date curves pixels wide
  Color hour curves
  Set style of hour curves to
  Make hour curves pixels wide
  Color background
  Color border area
  Color axes
  Make axes pixels wide
  Color grid
  Make grid pixels wide
  Color labels
  Enter text to display on the chart. Parameters such as latitude will be shown automatically.
  Optional text (e.g., location name)
  Additional text

Step 6—Choose file format for chart

  PDF (Portable Data Format).
We recommend this format, provided you have Adobe Acrobat Reader installed on your computer. PDF files can be easily resized to fit any printer page size.
  PNG (Portable Network Graphics).
This format may be useful if you want to save the image from your Web browser in order to import it into another document that will be published, projected, etc. Note that some Web browsers may be unable to easily resize an image in this format for direct printing. Usually, a landscape page with no headers or footers, magnified about 122% can be printed with good results.

Step 7—Click the 'Create chart' button

 

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© 2010, UO Solar Radiation Monitoring Laboratory.
Last revised: April 9, 2010.


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