Keying DTM to Floor Elevation?

[Taproot]

Assuming you have a DTM which has a benchmark elevation of say 100 ft. and you are trying to key it to the level of the First Floor Elevation ... how do you do it?

My layers are set up so that the first floor is at 0'-0". If I set the DTM at the corresponding elevation, the contour numbers will be off. If I move the whole building up to the 100 ft. elevation, then all of my perspectives are off.

Whatever insight you've got, I'm all ears.

[CipesDesign]

Hi Matthew, I have dealt with this issue a lot. While there isn't any "perfect" solution, there are (at least) a couple ways to do it:

1) Use "real" mumbers for your layer "z" values. In othere words, set your first floor to 102' (or whatever accurately corresponds to the topog data). The added benefit of this is that you will be able to easily annotate elevations based on an established benchmark, without having to do a bunch of math. The not-so-good thing is that whenever you change to a 3d view, you will need to go find the model (by scrolling up about 100 ft.). One way to make this easier is by using saved views...

2) This is the way I've been doing it for the last couple projects. Create your plan layers based on what you already have (eg: set the first floor to z=0), and then create a LAYER LINK with only the building layers in it (I call this Bldg Link). Then create a second LAYER LINK and in it put the Bldg LInk layer AND the DTM layer. Select the new link and UNLOCK it. Then you will be able to move the Bldg LInk up or down without moving the DTM. You can re-lock it afterward if you want.

Sorry if my explanation seems hurried, I am cooking dinner... Let me know if other questions arise...

[Taproot]

Thanks Peter,

Just out of curiosity, what is the advantage of linking the building elements and the site separately? It appears that if you unlock the link, you can move each layer of the link independently.

Now that I understand the approach, implementing it has been a tad bit harder. Whether it's my file or ... trying to implement the above has not only been crashing the program, but taking down my system as well. When I have more time, I'll follow up with NNA.

I hope dinner was delicious!

[CipesDesign]

The main reason I use two different links is as follows: because the DTM can take a really long time to render, I often use the "blgd only" link for a quick take, as I'm designing and making changes to the building. Then for more final views, with site, trees, roads, cars, etc. I can use the second link. Does that make sense?