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Revit sun altitude and simulation question

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    Revit sun altitude and simulation question

    Hi everyone:

    The revit sun altitude and simulation is different from the data of sun altitude calculation website.

    Time: 2016 21 Dec. 8am
    Location:Tokyo, Latitude: 35.6559982299805 Longitude: 139.654006958008
    sun altitude:10.50°

    However, I entered the same data and sun setting in revit, printed it and measure the angle of shadow is 23 °

    Clients really doubted the simulation result of revit.......

    Please to refer the attaching PDF

    Does anyone know how to solve it? Can any sun simulation or website be trusted?

    Your help would be much appreciated.

    Li :bb:
    Attached Files

    Hi, Apparently, the alternative you used to calculate your angle was from Google? I would trust Autodesk's data rather than google maps/earth, as they are normally based on official weather data from airports or some other institutions. Interesting to know nonetheless..


      Stating the obvious, you did hit apply didnt you? Works like a treat down here, but watch out for the use daylight saving button, it simply adds an hour all year round. Better to add an hour manually if in daylight saving time, and im guessing you are not in daylight saving hours at that date in tokyo? Just a thought. Oh, and the shadow settings are view specific, you didnt print off another view accidentaly?
      Last edited by biff; December 6, 2016, 01:07 PM.
      Motorbike riding is one long bezier curve


        Something must be off in the way you are measuring, or your sun settings of something. I just kind of eyeballed the longitude (got close to Tokyo) and set my time to 7:55 12/21/16 I was coming up with 9 or 10 degrees for the altitude shown in Revit.

        Jeff Hanson
        Sr. Subject Matter Expert
        Autodesk, Revit - User Experience


          Dear JeffH:

          Your help and explain are appreciated!

          How to set up the correct central line (green dash line) to measure the sun altitude in Revit? Is the angle of shadow different from sun altitude? Clients and I measured the angle of shadow is 23 degree and much higher than other sun altitude website 10.5 or 11.5 degree. Does it possible Revit show sun altitude directly in the simulation or drawing? It will be much easier to convince clients and reduce work if revit shows sun altitude directly.


          Attached Files


            I didn't use daylight saving because Japan doesn't have daylight saving time...! If I use daylight saving the result will be correct?


              It's a Geometry 1.01 problem, nothing to do with Revit.
              You are measuring your angle using a shadow being cast onto a wall that is on a certain angle against the direction of sunlight.
              Depending on that rotation this angle will vary. The sun altitude is measured on a surface parallel to the sun rays.

              Looking at the results your project north is rotated about 21 deg from the True North which is about 29 deg from the sun direction, that's why you're getting a different result.
              Attached Files
              Maciej Wypych

              Bibere humanum est, ergo bibamus!


                Ahhh, the old rotate true north watson!!!!!
                Motorbike riding is one long bezier curve


                  Thanks! it is easier to understand the idea of sun altitude in revit now!!


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