What is the best way to key building to DTM elevation?

[Taproot]

I usually set my first floor datum to 0'-0". It just makes the math easier.

Topography on the other hand can vary in elevation considerably. Let's say the first floor datum aligns to the model at 108'-0".

If you draw the two at the correct elevations, obviously they display 100+' apart. Do you then do a snapshot or a viewport to get them aligned correctly?

If you do, then drawing DTM modifiers gets tough to coordinate.

I'm just really curious how people do this.

Thanks.

[Kizza]

Simple answer:

Stories.

I set my storey to a datum level (such as Gnd, 1st etc) and refer my design layers to that storey.

you can also reference the building into the topography file...

[Assembly]

I'm on 2011 so don't know about stories.

I always keep the ground floor of the building at 0 for the Layer Height.

The DTM sits on it own layer. I set the layer height of the DTM to be the negative RL. IE If the RL of the building is 31.6M then my Layer height for DTM is -31.6M.

I have a DTM modifier layer with Layer height = 0.

When these are section view ported then you get everything in the right place.

On 2011 the 'Elevation Height' tool is relative to the design layer it is on, rather then 3D space (fail). So you have to be very careful using this as when you arrange your Section VP on your sheet layer, the Elevation Benchmark will change its reading.

[Taproot]

Thanks - excellent ideas. I'll try them both and see which works better.