topic Re: Project Preferences - Reference Level in Modeling

Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 07:16:45 GMT

I'm having trouble understanding how to setup a terrain using a Reference Level (AHD).

The attached survey shows the FFL of the building will be at RL 38.29, and the lowest spot level on the SS is at RL 36.58

In the Project Preferences/Reference Levels, what do I need to set my AHD Elevation to, -36000? being roughly 500 below my lowest RL??

Re: Project Preferences - Reference Level

Barry Kelly — Tue, 25 Jun 2013 08:09:01 GMT

Your FFL is best modelled at storey 0 (zero) at a height of 0.
So I would set the AHD level as -38.29.
That way you can reference heights in your model to the AHD and they will be accurate.
Barry

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 08:14:44 GMT

Barry I just want to making sure I understand this 100%. In other words, when I'm given a site survey, I would first look for a finished floor level, which becomes my AHD Reference Level " being my -elevation"

Am I on the right track?

Re: Project Preferences - Reference Level

Barry Kelly — Tue, 25 Jun 2013 08:30:55 GMT

That's what I would do.
I always set my main floor level at 0 and work from there.

If the floor level is above the datum you are using then set the reference level for that datum to the negative value of that datum level (positive if you FFL happens to be below the datum).

Now you can place elevation heights and reference them to the floor level or the datum depending on your needs.

Barry.

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 09:04:25 GMT

Ok so I've set the Reference Level to -38290, and clicked on the Mesh Tool and set the depth to 1000.

Is this so far right?

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 09:05:19 GMT

Mesh

Re: Project Preferences - Reference Level

Barry Kelly — Tue, 25 Jun 2013 09:22:50 GMT

Going on your figures you will need to set your mesh height to around 2500 so the base is lower than your lowest spot level.
Add the contours to the mesh and when you set the height for each contour (or spot level) make sure you set the height relative to your AHD.
Then you just need to type in the actual level - i.e. 38000 for the 38.0 contour.

See attached image but ignore the heights I used (just testing it myself).
Barry.

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 09:28:35 GMT

Yep comfortable with contours and spots, the part I get confused about is this mesh settings. So that 1000 depth I don't need?

Re: Project Preferences - Reference Level

Barry Kelly — Tue, 25 Jun 2013 09:38:39 GMT

Make it 2500 in this case.
If you are placing your flat mesh with the top a 0 (which is your AHD level of 38290) then you need to make it deep enough for your lowest level which you say is 36580.
So you actually need at least 1710 (38290-36580=1710) for the height - but make it 2500 so you are well and truly below the lowest level.
Then add your contours and adjust the heights relative to the AHD.
Barry.

Re: Project Preferences - Reference Level

David Shorter — Tue, 25 Jun 2013 10:40:41 GMT

Personally I wouldn't use this method, although if it works for you then fine.
The downside is that levels cannot be placed directly with the correct figure but have to have the text edited after placement

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 10:43:34 GMT

What would you do different David?

Re: Project Preferences - Reference Level

David Shorter — Tue, 25 Jun 2013 10:56:56 GMT

I would call story zero AHD and set this at 0.00
Set the lowest story of the building (say ground) at story one. Set the height to next from AHD to ground at the RL for ground.
Set the mesh on the AHD story with its top at RL zero
Add the levels to the top mesh to there real RL.
Then you place level dims using gravity to mesh and they show the correct levels without editing
Actually this is straight from the Australian template.
Hope this helps

Re: Project Preferences - Reference Level

Erwin Edel — Tue, 25 Jun 2013 11:12:18 GMT

If you use custom text on your level dimensions, you can just reference the correct level values.

In dutch we use "peil" (level), with that generally being the level of entry floor. So all dimension are shown as P+100 or P-500 etc etc. The only way to do this is to use autotext. For example

P<toPZvalue> = <toL1value> (<L1name>)

returns the distance to your project zero and the distance to your first reference level, with the name of that level in brackets.

For more thorough info see: http://helpcenter.graphisoft.com/guides/archicad-17-int-reference-guide/documentation/annotation/dimensioning/edit-content-of-dimension-text/#1056295

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 11:58:40 GMT

That's thrown a spanner in the wood works David

Let me try understand this on a novice level.

What your saying is that I would set the Mesh at Project 0, then create a new Story (Being Story 1), and setting its FFL height to 38290.

I then activate my Mesh Tool, draw a rectangle , and set the corners to the RL's given in the site survey.

If I'm understanding you correctly, this would create a very long "vertically earth, which will extend from 0 to 3920.

Am I on the right track?

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 12:13:05 GMT

Hi blimp, I recommend you watch this tutorial video on setting up reference levels with a mesh. I think it could be useful to you as it does mention Australian standards AHD.

http://www.acbestpractices.com/member-home/the-course/week-12/part-4/?inf_contact_key=9a3a2520de7a5d0559f8f55892451b349404034af9a85022c8449487a2764b6d

Re: Project Preferences - Reference Level

David Shorter — Tue, 25 Jun 2013 12:17:37 GMT

Sorry but you did ask.
The height of the mesh doesn't matter as you simply limit the depth extent of the sections and elevations and add a cutaway in the 3D view.
The benefit is that when you place a spot level using gravity it shows the mesh or slab or roof level correctly immediately without having to edit the text.
With this method you never have to worry that you have edited the text or remember to edit the text when you place new levels. The reference method is OK if you do it once but if you have to go back and add new levels it can become easy to miss something
17 is better than earlier versions insofar as the data shown in the info box is concerned.
As I said before if it works for you then fine .....the is nothing wrong with Barry's method I'm merely suggesting there are other options.

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 13:04:35 GMT

Strawbale I've actually bought into Eric's Best Practices Course and am well aware of the module.

The reason I posted the question is that I felt unsure, or better still just didn't get it!

I've used REVIT for the past 4 years, so I'm trying to be as fair as possible and learn ArchiCAD the correct way, that's why I'm here.

Barry's explanation has really helped, and believe I now better understand why you need to set the AHD to a minus Elevation, and start the lowest level at 0.

David's explanation is equaly interesting, I believe it's similar to how I currently do things in REVIT.

I recently showed Eric a project where I drew the Mesh at 0, but had no idea how to trim the earth beneath.

What Eric suggested I did was to draw a slab, raise it to "where I'd like to cut my earth", then do a SEO with a downwards extrusion.

Now that worked a treat, however I was interested in keeping my ground level at 0 so then it becomes easier when adding windows, doors or stairs.

Anyway I'll take this information onboard and give it a go

Re: Project Preferences - Reference Level

David Shorter — Tue, 25 Jun 2013 13:09:44 GMT

You might also consider some local training. Which state?

Re: Project Preferences - Reference Level

Anonymous — Tue, 25 Jun 2013 14:03:22 GMT

David I'm in Sydney as well and have already spoken to Graphisoft about available courses and their timetables, unfortunately it just doesn't fit in with my current position/timetable, which is why I bought the BPC.

Re: Project Preferences - Reference Level

Barry Kelly — Wed, 26 Jun 2013 03:24:22 GMT

David wrote:
The benefit is that when you place a spot level using gravity it shows the mesh or slab or roof level correctly immediately without having to edit the text.
With this method you never have to worry that you have edited the text or remember to edit the text when you place new levels.

I agree that is a good benefit.
The downside is you will need to adjust any elevation/section lines if they are limited to a particular height (i.e. internal elevations that are limited from floor to ceiling heights).
Then if you need to adjust your finished floor level you need to adjust the storey height, the limits on section/elevation lines and any 2D annotation you have in those section/elevations.
Unless I am mistaken and I'm doing it all wrong.

Seems neither solution is perfect.
What we really need is the ability to set the custom text in dimensions before we place them or even just the ability to save it as a favourite.
I am sure there is a wish somewhere for this.
I'll go looking and if there is not I will create one.
Barry.

Here are just a couple of wishes I found.

http://archicad-talk.graphisoft.com/viewtopic.php?t=37511

http://archicad-talk.graphisoft.com/viewtopic.php?t=27676