Forums >> Revit Building >> Technical Support >> Model coordinates/project datum

clkdmk

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We are currently designing an addition to a 3 story office building.  We are using a model developed by another firm to use in the creation of the addition so in the end the owner and contractor will have a complete model to work from.  the contractor will be using the model for 4d and 5d generation, and the owner's requirements or use for the model is still a work-in-progress and are not yet determined.  We are using Revit architecture 2010 but in the next 2 weeks (once all the other useres computers are updated we will be switching to 2012.

The original model was created utilizing the true building elevation and topo surfaces to create landscape, parking, etc. and is set at 625'-0".  Our office standards are to never use the actual elevation, and to start the building datum at 0'-0".  My questions/issues are below and any advice or recommendations would be helpful:

1. Senario "A" would have me linking the existing model into our standard template, assigning it a workset, and leverage it only for reference for now and bind when finished with the addition.   Senerio "B" would have me utilize the existing model, change to existing phase, and add on (not the prefered method due to the model size)
2. In senerio A and B, i would still need to set the existing building at datum 0'-0".  how do i go about doing this correctly, and if i do this, what impacts can you forsee down the line as we complete the building model and hand off to the contractor?
3. Is there a way that i can easily change the datum to 0'-0" for the exsting building and the new addition, and change it back to the true elevation 625'-0" before handing it of to the contractor?

Also of importance, we will be utilizing revit MEP and Revit Structure on this project as well, so the engineers will be linking the architectural model into their models, so any modification would also impact their work.

Thanks in advance.

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mbsteve

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Probably should change your office standard. Create your model at the correct elevation and position. This is not 2D Acad this is a simulation of reality, might as well start by making it on the real model.

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clkdmk

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I agree, that the 0'-0" is old school thinking and this might just be the catalyst for change.  So, lets say that our office bends and we use the true elevation datum of 625'-0".  Being that i have never done this before (office standard is 0'-0").  How do i set up the addition model to read the first floor datum at 625'-0" to match the existing model that i will link in?

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WWHub

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Read your HELP on relocating a project.  I also suugest you read the tdifference between shared coordinates and project.  That might help you.

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clkdmk

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I agree, that the 0'-0" is old school thinking and this might just be the catalyst for change.  So, lets say that our office bends and we use the true elevation datum of 625'-0".  Being that i have never done this before (office standard is 0'-0").  How do i set up the addition model to read the first floor datum at 625'-0" to match the existing model that i will link in?

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cbieser

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I think you want to utilize shared coordinates.  That way you can have your model located in real world elevations but also have it linked to your project elevations (ie. first floor at 100'-0").

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clkdmk

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the reality is that the contractor, their subs as well as the steel fabricators and shop personel, when faced with acual elevation numbers for the T.O. Steel, misc steel and bond beam locations are NOT going to want to read 635'-5 1/2" when in reality they want to see 15'-5 1/2" F.F.  when locating the building at the true elevation and tasking spot elevations or dimensions, you are left with true elevations.......which....once again, if you are on site, you are taking measurements from the finished floor, or from the footings or top of foundation.....NOT from sea level elevations.  Ultimately, i see what you are saying, but, it goes back to basicas and 0'-0" datum is the most efficient for the contracor. 

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WWHub

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OBVIOUSLY YOU DIDN'T READ YOUR HELP AS I SUGGESTED!

You can lead a horse to water but you can't make him drink!

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clkdmk

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Certainly no need to get testy!!!  I read what you suggested, but i'm not quite understanding it completely (just a dumb architect i guess) especially when trying to combine another offices model, that may, or may not be built correctly. 

This is obviously the first time that we have done this and i was just trying to gain some advice from others who have possibly done this before in order to model the addition correctly, the first time...... I thought that this would have been the perfect venue to post this question.  What i didn't expect was a condescending answer.  I guess i should try another Revit community to gain some professional help, rather than short answers.  My appologies for wasting everybody's time. 

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cbieser

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In the properties palette of a level head there is an option to choose shared coordinates or project coordinates.  If you Relocate Project while in an elevation or section view you can move the entire model to whatever coordinates you want to use (like 0'-0").  What WWHub suggested about the Help menu would lead you to the proper procedure to do this and be able to have both coordinate systems in the same model and make either information available to whoever needed it.

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WWHub

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I push people to read the HELP because it is a minimum background of knowledge.  (It is also very well written).  If you read that and still have questions, then at least we can talk with some common knowledge but to start from base 0 on something complicated is hard to do.

cbieser has given you good assistance.  I suggest you try this out in a sample - very simple project - where you can easily test and understand the process.  If you do that, the rewards will pay major dividends down the road.

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clkdmk

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Thank you cbeiser.  I appreciate your thorough answer.  Maybe this is where there's a problem, in that the original models levels aren't at 0'-0", but are at the true elevation of 625'-0", so instead of using a shared coordinate, the original model was literally built at a height of 625'.   WWhub was helpful in that he pointed me in the right direction, but after reading about the shared coordinates and applying them, my model 's elevations were still at 0'-0" but reading 625'-0" (as i imagine that they should be), which leads me to believe that the original model, was build incorrectly.  i have attached an image to help visualize what i am talking about.  As you can see, my levels start at 0'-0", but read 625'-0".  the existing model is attached and you can see that the existing levels are at 625'-0".  I'm assuming tht this is incorrect and that the existing model should have be built on the 0'-0" datum and referenced the coordinates of 625'-0" , correct?

Thanks

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clkdmk

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Stupid architect syndrome i guess, but...forgot to attach the image from my previous post.

Attached Images

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cbieser

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I don't think it will matter where it was built.  It should work like this:  Project coordinates are 0'-0", shared are 625'-0". 

Go to elevation view, select a level, edit type, change elevation base to shared or project.  Whichever you need to change is when you Relocate project which will prompt you to move it.  You should then be able to switch back and forth (depending on which information you need to convey) without having to affect the physical location.  HTH

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thetabest

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Just an FYI, open up an elevation view such that you can see your levels.  Select a level, and then go to type properties.  Within the type properties is a parameter which you can toggle from shared to project.  There is a disconnect on understanding or caring about this topic, but its there.

Project should be at the 0'-0".  Shared should be whatever height you are truly at.  This works with how the buildings are built, if you tell the contractor that he/she is to have a level at 625', they will have to convert it to the local project, in other words, they will change it to 0'-0". 

You CAN do it either way, but as your finding out, putting the building at the actual height prevents others from using the 0'-0" for the local project coordinates.  If you build your building at the 0'-0" and then place it in a site plan at the appropriate height/location, you can then add the shared coordinate system to your building.

Hope this helps

-----------------------------------

Trent Best

Best Systems

the.tabest@gmail.com

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