I *think* you're right about the angles. You don't need the angles in Sketchup though. There's a slider for month and a slider for the time of day in the Shadows Settings (Window -> Shadow). Just set these to the required setting and use the Tape Measure Tool (T, or Tools -> Tape Measure) to measure where the shadow ends. Or just guess it a bit, there are enough reference points on your drawing.

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You can actually put a picture from Google Maps under the house, but I obviously do not know your address, and Trelleborg was too large to search for a house with these precise specifications