Toposurface - Relative to true level, not project zero

[Andrew Dobson]

Is there a way to get the zero level of a toposurface to be anything other than the ground floor of the project? Moving the toposurface up and down just changes the spot levels such they always relate to the ground floor.

My ground floor is 8.5m above sea level, and I want the toposurface 0 to be related to sea level, not the ground floor of the building, so that I can add spot levels relative to sea level.

[tomnewsom]

Create a Level at 0 and call it "Sea Level" - in a view of this level, create your topo.

[patricks]

We have had this problem for years. Most projects in our area typically have a ground floor elevation anywhere from 250 to 450 feet above sea level. So while we can "relocate project" to get the level datums to show actual real word elevations, the internal points of the toposurface ALWAYS display elevations relative to the project, which is usually the ground floor (ground floor = 0 in the project most of the time).

To get around it, many times we end up just having the toposurface floating way above the building. This is not ideal, because then we cannot use the toposurface in our details and elevations to show the ground plane.

Another method we have done is actually reverse the project and shared elevations - that is, the whole building will move up to whatever elevation (say 300 feet), and then I will relocate the project back down 300 feet and change my levels to report shared elevations. That makes the level datums actually report the project elevation (ground floor = 0 feet) and the topo's internal points will report true elevation. The drawback here is that it's really not correct, and it also takes some work to get the contour lines to display in the correct location if your finished floor level is located between a whole-numbered contour line.

The solution I have discovered is having a separate model for your site topography. Have this file contain ONLY your site survey and topography, and maybe building pads, but nothing else. By doing this, and acquiring coordinates from the CAD file and sharing both the building and site models, you can then link your site model into the building model, and just move it up or down to get it in the right place relative to the building. Then you can link your building model back into the site, it will automatically appear in the correct location, and you can grade your site in the site model with true elevations displaying on the internal points.

Another cool thing is that you can do spot elevations for the site in the BUILDING file, and it will display the correct true elevations of the linked toposurface!

This is the first project we have taken such an approach on, and it's really looking promising. Another plus is that the person grading the site can change the units in the site model to engineering decimal units, while those working in the building file can leave the units as normal feet/inches. I know that doesn't apply to you metric folks, but it's a big plus for us imperial folks.

Here's the thread from a couple weeks ago that gave me the idea to do a project like this. See the 2nd post for the preferred work flow. I followed those instructions for getting everything set up and it has been working just fine.

http://forums.augi.com/showthread.php?t=92171

[Gadget Man]

The solution is childlishly simple!

When you open your default template, before you do anything else, change factory preset "LEVEL 1" to "DATUM" ("Sea Level", "AHD", or whatever you want to call it) and make sure it is elevated at 0.00. Set it as shared level if you wish - for future coordination between linked files. I also recommend pinning it at this point and even making it invisible, so nobody else is tempted to change it...

Then change factory preset "LEVEL 2" into "Ground Floor", "Building Pad" or whatever you want to be your lowest project level and set up its elevation as desired. Set up this and every next level created as project based.

Create all the other required/necessary (project) levels, name them and set up their elevations as needed.

Make sure that your SITE PLAN view (or the view in which you create your toposurface) is based on your 0.00 DATUM (shared) level and NOT on the Ground Floor or any other project level.

Everything then works just fine.

And you may save it into your template, so you don't need to re-create this scenario every time.

[Andrew Dobson]

Create a Level at 0 and call it "Sea Level" - in a view of this level, create your topo.

This doesnt work, it always creates the topo levels relative to our ground floor no matter where sea level is.

I contacted Autodesk, and they said that this is a known issue and have put it on their wish list.

A work around could be in the template file, make Project Zero (ground floor) at sea level, then when you start a new project, create a new level at the true elevation of the ground floor, way above project zero.

This requires you to know the height above sea level of the building at the beginning of a project, which is a pain.

[Gadget Man]

This doesnt work, it always creates the topo levels relative to our ground floor no matter where sea level is.

I contacted Autodesk, and they said that this is a known issue and have put it on their wish list.

A work around could be in the template file, make Project Zero (ground floor) at sea level, then when you start a new project, create a new level at the true elevation of the ground floor, way above project zero.

This requires you to know the height above sea level of the building at the beginning of a project, which is a pain.

Make sure that your Site Plan view is NOT based on your "Ground Floor" but on your "Sea Level". This is crucial!!! Once it's created based on the wrong level you can't change it, so make sure that you work of the correct level when you create your Site Plan view.

[Gadget Man]

...This requires you to know the height above sea level of the building at the beginning of a project, which is a pain...

No, it doesn't.

When you set up your DATUM (shared) level the way I described earlier, your project's bottom-most level can be set up initially at whatever you like - even at 0.00, although this may be a bit confusing and should be avoided because it would overlap the DATUM level...(you would have two levels one on top of another). I usually set it up at 20.00

If you attach everything in your model to the levels correctly (as you should) and lock the distances between the levels it is very easy to move your levels up or down later and your model follows. And I don't even use in-built function "rellocate project" - never had.

This is really very simple and works for me every time!

Let me know if you need it and I will attach some pictures describing this process in detail.

[patricks]

No, it doesn't.

When you set up your DATUM (shared) level the way I described earlier, your project's bottom-most level can be set up initially at whatever you like - even at 0.00, although this may be a bit confusing and should be avoided because it would overlap the DATUM level...(you would have two levels one on top of another). I usually set it up at 20.00

If you attach everything in your model to the levels correctly (as you should) and lock the distances between the levels it is very easy to move your levels up or down later and your model follows. And I don't even use in-built function "rellocate project" - never had.

This is really very simple and works for me every time!

Let me know if you need it and I will attach some pictures describing this process in detail.

While this method does seem to work, it doesn't allow your levels to display the ground floor elevation as 0.00, as is typical in our region. While we have done some projects in which the levels all show actual elevations, it can get confusing when reading sections and elevations, particularly if bearing heights and other levels are at some odd number above the ground floor level.

For instance, we might have our 2nd floor at 11' - 7" above ground level, and the top of steel for that floor's structure is going to be 6 1/2" below the floor level, or 11' - 0 1/2". Now say that the project is like the one I'm working on now, which has a finished floor elevation of 226.43' above sea level (matching an existing building).

Now if my project was set up as you describe, I would have no choice but to have my levels display 226.43 for the ground floor, 237.47 for the top of steel, and 238.01 for the 2nd floor level. Now I'm pretty good at math, but even I would have to use a calculator to figure out what that is in feet and inches to get my floor heights and steel heights. And if I have to do that, who knows what the typical GC or sub-contractor is going to go through. I would have to put an actual dimension between all level datums on all of my section and elevation views.

At this time, the method with linked files is the only way to get the topography in the correct place relative to the building, AND have the topo's internal points display the correct sea level elevation while editing. It also gives you the option of displaying your building levels with the ground floor as the 0 datum, since every vertical dimension in the entire building references the ground floor level. In this region of the world, it just makes our CD's easier to decipher.

[Andrew Dobson]

No, it doesn't.

Let me know if you need it and I will attach some pictures describing this process in detail.

This would be great if you have time. I think that this a confusing and frustrating issue for many people!

Thanks and Happy Christmas

[Gadget Man]

This would be great if you have time. I think that this a confusing and frustrating issue for many people!

Thanks and Happy Christmas

OK, that's not a problem but in the new year - right now I leave for a two-week trip and I won't have a chance to do it. I am sorry.

Have a peaceful Festive Season and a happy New Year.