True north in Geo-location

It took many years of confusion until I learned why the geo location terrain looks rotated in the model, and why geo locating changes the north angle. For those who don’t know, geo locating a model in SketchUp makes the model green axis match something called Grid North. I have personally never heard of Grid North outside of SketchUp’ geo location - not in architecture school, not in my internship, not in high school, not in elementary school. Grid north doesn’t even have a page on Swedish Wikipedia.

The idea of Grid North seems quite smart. If I understand it correctly, you divide earth’s surface in segments where you approximate the surface as singly curved. This allows two parallel lines to stay parallel, but at the cost of north jumping a few degrees when you cross the border between two segments.

The problem to me is that Grid North just doesn’t seem to be widely used here. Every time I’ve geo located a model and imported a DWG plan, site plan or city plan, it has been oriented with True North as its Y axis. Every time I’ve had to either rotate it to match SketchUp’s solar north direction (with some custom Ruby snippet for precision), or reset solar north to 0 and also rotate the terrain/map snapshot accordingly.

I propose making geo located models use green axis as True North, or at least make it an option when geo locating. Not only would this make my life easier, but it would also lower the learning curve and be a lot easier to make sense of as it follows the principle of least surprise.

Who knows, maybe simplifying this also makes the SketchUp devs’ life easier.


Related threads:

I’m not the first person to be confused by the grid north noise.

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Here’s another for the list…

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Maybe it’s a vestige of how Google Earth satellite photos were tiled as images onto SketchUp models? Of course, with that feature gone, why stay married to it. Does the new system need image tiles or something dictating this?

Google Maps uses true north so it would have been simpler to just stick to that in SketchUp from the start. I don’t know why they went through the extra problem of using another north in SketchUp.

Hi, I also mostly work with survey data that is written to Sketchup through FME translator. In this case the TrueNorth angle is needed to be applied to the written sketchup model for relevant terrain cutout area to match the 3DCityModel of Stockholm.

Looking at other 3D software programs e.i. 3dsMax, I’m just spawning ideas of how most of them do not work with geo-located coordinates, as the purpose is mostly to model object based models (charachters, assets, details etc.). So you have to world coordinate origo that every object relate to and then you can set local coordinate to each object’s orientation in 3dsMax. Same as 3dsMax, you can model object based models in Sketchup as well and then you’re probably well with GridNorth.

If I understand it right, TrueNorth in Sketchup is also for getting accurate shadow analysis for geo-location all around the world?
So depending on model purpose in Sketchup, maybe it would be good to have a switch button between GridNorth vs. TrueNorth?

I found this discussion link pretty interesting too for north angle in sketchup:


I have stumbled on this thread as I am relatively new to SU and haven’t needed to use Geo tagging until my wife has decided on a summer/garden house and wanted to know about how much sunlight she could expect at different times of the day so I started to explore shadowland geo location. I managed to sort it out and found the green global axis is a very good approximation of true north.

That aside I am an ex-military pilot and the 3 main Norths we use (yes there are many ways to define it) are True, Magnetic and Grid. True North is located at the Northern axis of the Earth’s rotation, is permanently fixed (in practice) and is laid out on maps using various projections - mercator etc- which you can research if you want. If however you need to use a magnetic compass to navigate you must understand that the needle points to magnetic North which is not located at True North that moves at a fixed annual rate, is different at various points on the Earth’s surface and is quoted on maps and charts as an isogonal - basically lines of equal magnetic variation. Using this variation you apply it to the true track you measured to navigate and add or subtract it to give you a reading you must set on the compass, so if the variation was 15° you would head off on a magnetic heading on the compass of 345° or 015° dependent on whether the variation is East or West of True North to make good a measured True heading of North.

Grid North is the map producer’s way of laying out the topography of a section of a sphere by laying it flat and applying a square or rectangular grid overlay set for their convenience orientated as close to True North as practicable. It is treated in the same way as True north but instead of magnetic variation you use Grivation, Grid variation which is also displayed on the map/chart along with mag Variation.

Any way I hope this highlights the mystical/mythical Grid North which is a real thing and also very practical.

Keep safe

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