Multiple datums?

[will9ESP8]

I tried searching but didn't find an answer yet... or some confusing ones...

I have a drawing with 2 stages, and a lot of stuff laid out on each stage, including blocks which display X and Y coordinates from the datum. When I go to lay out these stages I need a datum to start from on each stage. One way is to move the entire drawing back and forth from one datum to the other, but this is a pain and is easy to miss moving something. I'm guessing there's a better way.

For now I just have 2 drawings going, one with a datum on one stage, and one with a datum on the other stage. 

Is there a way to have 2 different datums, and I can select which one the blocks are pulling their coordinates from, regen the drawing, then plot? Or do ya'll suggest a different way to go about this? Thanks,

[imadHabash]

Hi,

>> For now I just have 2 drawings going, one with a datum on one stage, and one with a datum on the other stage. 

How about start convert those stages for xrefs and start attache them to one origin host drawing. when you need one stage you can unload the other one and so on. For printing issue you can put datum in different layers and from layout start making viewports for those datum with specific layers.
If you want any more details, get back here and ask your need.

[paullimapa]

The way you're describing datums sounds like floor plans.

If drawing everything in the same drawing:

Typically for floor plans we would have all the objects that show up placed onto layers that uses the same modifier so these layers would always be on for all floor plans.

Then have unique modifier for different floor plans. 

Now we can turn off layers we don't want to see based on the modifier.

Or you can draw the different floors in different drawings and then reference everything into the same drawing file.

Then again use layers now prefixed with the drawing name to turn off vs on for different floors.

[AllenJessup]

As @paullimapa mentions. There seems to be some question on how you are using the word Datum. Also why would you need to use two distinct datums? In Surveying and Civil Engineering having two Datums on one project would mean thing would go very badly during construction.

[Kent1Cooper]

You can do this very easily with ORDINATE DIMENSIONS [read about them].  Just change the UCS origin to the appropriate datum point for the stage in question when you place them.  You can even drag the datum origin point of an already-drawn Ordinate Dimension [there's a grip there] to a new datum location if you need to, and it will update.  Save the UCS for each stage with a name, so you can easily switch between them [or among them -- you can have as many as you want], and back to the WCS, etc.

[CodeDing]

@will9ESP8 ,

I believe @Kent1Cooper probably has the best approach that you are looking for.

Although a datum is a generic term, it is commonly used in the world of Land Surveying / GIS / Geodetics. It sounds like you are using it synonymously with UCS in terms of AutoCAD.

Best,

~DD

[will9ESP8]

Hey guys,

Thanks for all the replies. I was in the middle of a gigantic project as the on site lead, and upstream of me the drafting end fell apart, and it landed on my shoulders to run the site, but also re-draft as we went. It was a horrible couple of weeks, with very little sleep. Anyway now I'm through it and want to go back and learn the right way to do these things to make it easier from now on.

What I ended up doing was along the lines of what imadHabash suggested above. I made one master drawing, where I did everything. But, I made 2 more drawings, where I simply X-REFd in the master drawing. However, in these new drawings the datum was in a different place for each. Worked fairly well.

The reason I needed to do this, ie have two different datums, was that my blocks have an X and Y coordinate built in. On stage 1 I needed all the blocks to reference a datum upstage center of that particular stage. On the second stage they needed to represent upstage center of that particular stage.

I wonder if the better way to do it is how Kent1Cooper suggested. I'm probably using UCS and Datum wrong at times. It's cool that you can save multiple UCS with different names. However, the blocks I made have a field for X Coordinate and Y coordinate via attdef - insert field - object - position - then select X or Y. This seems to reference the 'world' ucs which I suspect is the actual datum. I just tried making a new UCS, and when I type RE they don't update  - the coordinates are linked to that original datum. Does anyone know if there is a way to make the coordinates reference user defined UCS's instead? That would be slick and save me having to make more drawings. Thanks,

[Kent1Cooper]

Investigate the (trans) AutoLisp function.  It can convert [translate] coordinates from one Coordinate System to another.