Snap Station Value Down To The Nearest

The Plan Production tools are tricky. I recently spent quite a while troubleshooting a plan & profile sheet (and related styles) only to find that the error was in the “Snap station down to the nearest” value. I’ll try to explain, but this is a rough one.

Typically a profile will have space to the left and to the right for datum labels as shown below:

And typically whether your profile grid is placed on an 11×17, 22×34, or 24×36 sheet, you can configure the grid to be an even number of paper space units wide. For example, on an 11×17 sheet you can place a grid roughly 15 1/2″ wide, with two roughly 3/4″ wide bands to the left and to the right. Depending upon your title block configuration, this will allow you about 3/8″ to the right and left of the sheet for a border, about an inch for title information (if placed on the right side of the sheet), and about 14″ of clear span to show profile data – give or take. In any case, it will be tough to fit in an extra inch for a profile view in the center of the sheet, and the math is definitely important if you want the Plan Production tools to do the thinking.

Make your plan and profile viewports the same width (if you’re concerned about the “text box,” don’t be, it no longer plays a role), make them wide enough to land you on an even station, and add the widths of the two datum columns. When you finally run the plan production tools you’ll have a great chance of things working properly. But not if you don’t properly configure the “Snap station value down to the nearest” value. if you’re queasy, you may want to stop reading now…

In a 14″ viewport, with a scale of 1″=40′, you’ll fit about 504′ of profile and a couple of 3/4″ bands. But you’ll need match lines. Match lines are typically best at even stations, so in 504′ you’d like to place a match line at a 500′ interval, and common sense might prevail and you’ll set the snap value accordingly (50′ or 100′). But it won’t work. Why? Civil 3D will attempt to place a match line at 500′. But with a viewport 560′ wide, Civil 3D won’t know how to react to the slop, so it’ll throw the profile view somewhere in the middle (to the right), and I can guarantee it won’t be right (plan and profile views won’t line up). You’ll find the same result if you try to set the value to 100′ – again, Civil 3D won’t know how to react to the slop. But if you set the value to 80′, Civil 3D will snap back to a value divisible by 80, will add the distances for the datum columns, and will place profile views dead center of the viewports. Match lines at 0+00, 5+60, 11+20, 16+80 (not ideal, but workable) – add about 3/4″ on either side, toss the view in the middle of the frame. Perfect. Makes perfect sense.

If you’re a mathematician.

Try this: Make your plan and profile viewports the same width. Keep the clear span of the profile grid an even distance (to land on an even station, e.g. 10+00 or 10+50). Keep the datum columns (this is assuming you have them) an inch or less wide, and if you’re having trouble with placement like I did, double the scale of the drawing to set the “snap down” value. In a 40 scale drawing, try setting the value to 80. In an 80 scale drawing, try setting the value to 160, in a 100 scale drawing, try setting the value to 200, and so on. Civil 3D will back off the match line placement to an even station value that will fit in an evenly spaced viewport (14″, 15″, 16″, etc.).

If you’re wondering how to place the horizontal datum lines to the left and right of the profile view, they’re simply tick marks – long tick marks. There are no vertical lines on the datum columns in the profile views (wouldn’t that be nice – would be nice in section views as well), you’ll let the profile viewports take care of that.

Scott McEachron
www.121pcs.net

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