SketchUp’s model space embodies a three-dimensional Cartesian coordinate system.
By default, everything you do in SU correlates with the inalterable x,y,z world axes.
I.e.
• Inference Engine
• Inference Locking via Arrow Keys
• View-based Tool Alignment
• Camera > Standard Views
• True North for the Shadow Engine
Best practice is to keep it simple. Model on-axes along the default x,y,z world axes and leave it there.
Use the intrinsic relationship of the tools to the world axes to your advantage, rather than fighting it.
Geo-location via Add Location and subsequently rotating the model as you describe forces you to work off-axes; merely to accommodate imported GE terrain, which as you say, is neither necessary nor desirable.
Manual geo-location empowers you to leave the model properly aligned with the world axes.
Window > Model Info > Geo-location > Set Manual Location…
Then, use the Solar North tools to establish the proper relationship of true north to the model.
From what I gather, all you require is a simple flat face painted with an aerial image of the tract.
Let’s say you draw a large circle whose center is at the Origin.
Group the circle and then edit the group; painting the face with an aerial image material.
Then, use the Texture > Position tools to scale, rotate and position the image.
Bear in mind…
• It’s only an image. Its position has no affect upon geo-location and resulting accuracy of shadows.
Consequently, absolute accuracy in positioning the image isn’t necessary.
• You’re no longer limited to the aerial images from GE, which at times, aren’t the nicest.
There are plenty of other sources of aerial imagery.
For example the images of downtown Lake Geneva from our Walworth County GIS Online Mapping System are much more appealing than the current GE imagery.
GE Snapshot
WalCo GIS Imagery
Summary
• Model on-axes along the default x,y,z world axes
• Manually geo-locate the model
• Use the Solar North tools to rotate the direction of north rather than rotate the model off-axes.
• Use an imported aerial image material applied to a face in lieu of the GE Snapshot.
• Confirm all the relevant settings are correct for shadow studies.
I. e.
• 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.
More about shadows and manual geo-location here.