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Civil 3D stuff – starting with cogo point scale factor, leading to helpful info from others
While working on a topo and hovering over a cogo point I noticed it had a scale factor (SF) on it:
This model started from a previous job which had geolocation set. This current project didn’t need it, so I removed it, and the SF’s went away.
However, looking into the previous job a bit further, the coordinates and SF seem weird, as the actual geolocation of the site was 17S … but the Civil 3D edit point data seemed to refer to something a lot colder:
Anyway, found this interesting blog, which has some good tips in it, including a routine for plotting tree size from point codes, and good stuff for corridor modelling:
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5 Replies
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1.026 is a freakishly large scale factor.
I’m not sure what that means, but I would be extra worried about my coordinates.
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Central meridian E177d the point is at E199d? something isn’t right.
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Yep, and there’s S53 in there too, however actual point coordinates are all ok, so not sure what’s going on here. I wonder if it is related to the “Survey” functionality of Civil 3D, which we don’t use.
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Looks like the wrong UTM zone might have been chosen, causing the giant scale factor. Project settings were not applying the factor anyways, per the second image (and the N/E of the points being the same as the Grid N/E).
C3D is getting better at working with geodetic data, but considering how much pain can be caused by someone messing with drawing settings, we tend to go unitless and “No Datum, No Projection”. We put the metadata, geodetic basis for coordinates and transformation parameters in the drawing and on the face of the deliverables, and keep everyone working in a simple 3D system. For bigger projects with lots of contributors from many disciplines it seems to keep us out of trouble.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman -
I would say it’s your set-up. That reference point #.
C3D went through a time where it would scramble the set-up #.
It was probably copied from one job to another with the scrambled #.
If this is all GPS then I would be sure that the lat, long, NE all work in the GPS data, still a convergence angle of 18d is not what you are looking for.
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