Sun Angle Issue


Recommended Posts

I have followed instructions for plotting the sun angle but getting strange results.  I set my north arrow correctly relative to the house and lot.  I put in the latitude and longitude for west of Boston MA.  I chose Dec 20 2015 at various times of day and it seemed a bit off.   To test, I chose 7pm.   When I hit "make shadow" it shows a shadow at 7pm (screen shot attached) even though the sun sets at about 4:15pm.  How can there be a shadow?


Link to comment
Share on other sites

For those that may not already know this......


LAT and LON for any spot on the planet could not be easier. Use Google Earth. If an address is known, type it in and fly right there, otherwise navigate to location. Once location is found, center cursor over spot (house, field, wherever) and look at bottom of page where LAT LON is very accurately given.


LAT and LON are bottom of page. Now, in CA, "Sun Angle Specification" simply use this information and your house is now geo specifically placed on planet.


See example photos attached. 


This post was edited to correct an error I had in my explanation. If anyone read it previously, I apologize otherwise, what is written above is correct, as well as what Glenn says one post below.



Link to comment
Share on other sites

42º 23'44.56" N is just as accurately written 42.234456º N


71º 05'11.66" W is equal to 71.051166º W







This is not correct.

The conversion between degrees, minutes and seconds and decimal degrees is a bit more complicated.


The conversion is D(dec) = D+M/60+S/3600


You can't just use the same digits and ignore the formatting..


Chief can handle the conversion easily by using Number Style in a dbx. 


eg,  42° 23' 44" converts to  42.395556° using this feature (not 42.2344º). 

Link to comment
Share on other sites

Looking at this further, you'll note that Chief drops everything to the right of seconds decimal place. If entered CA does not round this number, it simply drops the numbers to right of decimal. Example is 37.96" will get entered by Chief as 37" This can potentially be an error of 100' give or take. Not a big issue as far as sun angle goes, but if a specific location is desired, say a townhouse, you would not want to be pointing at a neighbor 3 - 4 houses over.  


If more accuracy is desired, and again for sun angle this really does not matter, entering degrees as a decimal will be spot on. You can use Glenn's formula above, but I found this online converter that will also do this here >>


Within CA "Sun Angle Specification", change "Number Style" to "Degrees" 


CA will trim this to 6 places to right of the decimal, but will be right on for your target.


Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in

Sign In Now

  • Member Statistics

    Total Members
    Most Online
    Newest Member