0'-0" (Top of Slab/story settings) or M.S.L. actual numbers?

[rob2218]

well, we are faced with the following question:
1. Do we use a 0'-0" story vertical elevation for our top of slab reference point....or
2. Do we (can we even force Archicad to do this?) use the actual M.S.L. (mean sea level number) as our top of slab, story setting and subsequent stories above and below this reference number?

Reason for this question is cause one of our sub-consultants wants to establish a "top of slab" as the 'actual Mean Sea Level' number vs using the top of slab (story setting) at 0'-0" and then referencing 0'-0" to a M.S.L. actual number.

Please advise on where I can make these "global" setting changes and what issues it will have on out database.

[David Maudlin]

Rob:

I am not 100% on what you want to accomplish here (a screen shot of what you are trying to achieve would help), but you should start by looking at Reference Levels in the Help files, they allow you to assign different values for heights for the tools that use vertical dimensions (Level Dimension Tool, Sections, etc) including the ability to switch between Reference Levels for input and placed dimensions.

David

[Anonymous]

As David says you can set a sea level reference elevation the allows you to retain your project zero at top of slab while still referencing dimensions to sea level.

There are odd occasions where this doesn't work and I have created a bottom story at sea level and arranged the others relative to this. You can also combine the two methods by hotlinking the architectural model into a site model that has sea level as it's project origin.

[rob2218]

Where is it that I can access the "reference" elevation settings?
And does this at all have to be set in all hotlinked TW files I have going on?

This project contains 3 hotlinked TW files (errr..well, databases).
All 3 hotlinked TW files are hotlinked into each other with skipped nested references.

Now...if I adjust the "reference elevation" (where that is I don't know) but if I adjust this number...will it wig out the other hotlinked TW files? or will I need adjust the same "reference elevation" settings to all 3 so they all play nice with each other?

[Laszlo Nagy]

Check the following ArchiCADWiki article about Reference Levels:

http://www.archicadwiki.com/TechNotes/How%20to%20Display%20Elevation%20Values%20Relative%20to%20Sea%...

[rob2218]

thanks Laszlo,
much appreciated. that's a good write up.

[David Shorter]

I've always struggled with the reference level concept. Why? because the Info box never displays these values, so you are working with 2 sets of levels, and when levels are placed using gravity (say to slabs) you have to modify the settings afterwards. I think its much easier to set a story for project Zero and leave this at 0.0 then put the height to next from this to the Ground Story as the correct level.
Using this method you are only using one set of levels and the Info box and all the dimensions show the correct levels.
If the level of the building changes this can be done by changing the height to next Project zero to Ground and everything changes....

[rob2218]

Agreed.
i think the story setting should be set to 0'-0" if this is the "first floor" let's say.
That way you simply equate 0'-0" to a MSL (example 0'-0"=M.S.L. 194.5')
and if the MSL goes up or down or if your building slab needs to be moved up or down...it's based on a 0'-0"=something number.....rather than having to actually 'show' the real world vertical mean sea level number all the time.

But what's happening here is we have a structural engineer who insists on switching over ALL our story settings to the "real" mean sea level numbers. What a nightmare that's going to be for the contractor when he has to figure out and add up strange fractional numbers because our structural engineer decided "IT MUST BE THIS WAY".....

[David Shorter]

Hi Rob
I'm not sure we do agree. I'm saying keep the slab at zero to its home story (ground or level 1 whichever). Make that story at 194.5' (that is 194.5' above Project Zero) so the top of the slab is at 194.5'
MSL does NOT move this is a survey datum . In Australia its called AHD (Australian Height Datum)

[rob2218]

ahh...I see. misread your comment.
what's the process for showing (indicating in Archicad) that 0'-0" (top of slab) is actually 194.5' MSL?

And what does this do to the model?
Does it throw off all of your views? Now that your datum point is actually 194'-6" higher than the views you created?

I'm not clear as to what 'global model' effect setting a different "top of slab" at a different number other than 0'-0" (if we are only using the first floor top of slab as the base example) will have on the views, perspectives, elevations...etc...??