Sun positioning is wrong


#1

Hello,

I am an amateur designer and I have already done my whole house in sketchup. I often draw designs there before I do my DIY projects, such as my pergola. Now I am studying the affect of installing a shade sail on my backyard and I discovered that the sun positioning for UTC+'s is wrong. Nowhere seems to get direct light when I set to UTC+10:00 (Melbourne).

I have already positioned my model with the right north coordinates, with the front of my house about 20 degrees higher than west. The light seems to work fine for UTC- but the sun position is somehow coming from south. I even tried flipping my model upside down but it didnt seem to work. Changing the time of the shade will cause some areas to light up a bit but it still not working right. Is that a known issue? can I set the position of the sun manually?


#2

…I have already positioned my model with the right north coordinates, with the front of my house about 20 degrees higher than west…

What do you mean by "with the right north coordinates. It’s either the north angle (more is needed though, i.e. both north(south)/east(west) coordinates) or the north (or south) plus the east (or west) coordinates (north angle is also needed)

Did you “add location” to your model to also get it geolocated correctly?
This will put your model in the right spot on the earths surface with correct north angle.
Next you need to rotate “just” your geometry to fit the imported Google Earth image. Its facades may be not parallel to red and green anymore. As in the real world.


#3

Hi Wkcavallari,

Current local time in Melbourne is UTC+11
Daylight Saving Time (forward 1 hour) went into effect back on October 5, 2014

Here’s a handy Global Time Reference

North is but one of four parameters you must verify to display shadows that accurately portray the real world.
• Geographic Orientation — Relationship of True North to the model.
• Geographic Location — Latitude and Longitude
• Time — Year, Month, Day, Hour and Minute
• UTC Offset — The difference between local time and the Coordinated Universal Time standard.

It’s not clear how you geo-located the model.
Did you use the File > Geo-location > Add Location feature?
Or did you geo-locate the model via Window > Model Info > Geo-location > Set Manual Location?

Do you mean 20° True or 20° Magnetic? … It’s vital you understand the difference.
Magnetic north in Melbourne is currently >11° east of true north.
All directional information in SketchUp is in True direction.

Here’s the magnetic declination data from the NOAA link below:
Melbourne Declination Data.pdf (178.4 KB)

Global Magnetic Declination Calculator — National Oceanic and Atmospheric Administration USA

Here’s more about creating Accurate Shadows in SketchUp

-Geo


#4

Hello @wkcavallari,

Here’s a properly geo-located model for you to examine.
The astronomical reports you see in the model were generated from the USNO Data Services links below.
The local time in all scenes is 13:06 pm which is Sun transit aka solar noon.
Click through the scenes to compare the USNO data to the model.
You’ll find SketchUp’s Sun is right where it belongs.

Melbourne Example.skp (235.3 KB)

United States Naval Observatory Data Services — Home
http://www.usno.navy.mil/USNO/astronomical-applications/data-services

Complete Sun and Moon Data for One Day — USNO Data Services
http://aa.usno.navy.mil/data/docs/RS_OneDay.php

Altitude and Azimuth of the Sun or Moon During One Day — USNO Data Services
http://aa.usno.navy.mil/data/docs/AltAz.php

-Geo


Shadows not working in model
Shadows not working in model