Coordinates and units

[marko.rintamaki]

Hi all.

Im new to this forum and thought why not ask here also pretty new to geolocation coordinates in autocad 🙂

I have autocad drawing using ETRS GK27 geomap and model is in correct coordinates. ETRS GK27 uses metric values so that 1 unit equal 1 m.

is there a way to input values as mm when you for example draw a line so that it will be 1 unit long in model? Dynamic input does not seem to allow me to type 1000mm for example. What would make 1 unit lenght of a line.

1000 input value for 1m line is out of question because it would mess locations to ETRS GK27 locations.

Atleast dimensioning can be scaled to give 1000 lenght to 1 unit long line.

Hopefully you understand the question, don't know how to better decribe what im after. I just wish I could draw inputting mm values and it would still match with ETRS GK27 system. Also if I remember right in Microstation this can be done throu master units/sub units. (not 100% sure about this).

-Marko

[imadHabash]

Hi,

>> ETRS GK27 uses metric values so that 1 unit equal 1 m.

>> is there a way to input values as mm

The only way is to scale your drawing and that of course ( in your case ) NOT recommended ,  So the answer is NO . 

>> 1000 input value for 1m line is out of question because it would mess locations to ETRS GK27 locations.

You're right . 

>> Atleast dimensioning can be scaled to give 1000 lenght to 1 unit long line.

entering new value for DIMLFAC (System Variable) will do that . 

>> I just wish I could draw inputting mm values and it would still match with ETRS GK27 system.

the only way as i said is to scale over all of your drawing and that's NOT recommended . 

BTW ... why is your need for inputting in mm since your drawing units are in M ?

[ian.mag]

Hey,

I would suggest you use the drawings (with the ETRS GK27) as an xref in an acadiso.dwt drawing. That way, you can use the mm units comfortably without having to scale the drawing. Please not that while you insert the dwg drawing to the metric drawing, AutoCAD will detect the units that you using and scale the drawing for you without losing anything.

Try this and let us know what you get.

[imadHabash]

>> AutoCAD will detect the units that you using and scale the drawing for you without losing anything.

Q: What about coordinates ?!!!

[ian.mag]

Hey,

I stand to be corrected but I tend to think the "same factor" shall be applied uniformly to the entire drawing, such that it's as if you are working with mm as opposed to meters.

Otherwise, let him upload the drawings for testing.

[marko.rintamaki]

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BTW ... why is your need for inputting in mm since your drawing units are in M ?

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We use the master dwg what is drawn at correct coordinates with metric units in a few other drawings as a reference. But those other drawings are drawn with mm units. Now that when the xref is scaled and even moved in other drawing it will break those coordinate labels Ive made to master file. Was then wondering if there is some way to play with the units without affecting coordinate system. Seems it is not really possible.

I decided to xref those other drawings to master, because they can be scaled etc.

I started with a wrong foot this project 🙂 Thank you all for your input.

-Marko

[ChicagoLooper · Accepted solution]

OK, I see that your site is in Finland and it sounds like you have a design drawing that you want to georeference to the real world. Correct? Your site, which sits in modelspace, has been assigned ETRS-GK27 so it's relegated to drawing units of meters and anything in modelspace should have, and will have, dimensions that comply with those drawing units, otherwise they won’t be sized correctly. Your design, or someone else's design that you have been tasked to georeference, is in millimeters.
 
You have three major considerations when geolocating your line work:
1. Location. This involves relative position against both the equator and prime meridian (or some other line of longitude).
2. Rotation. This involves orientation, whether it is parallel or perpendicular to the equator. Many times, it’s neither but somewhere in between.
3. Scale. This involves drawing units, and as you already know, can make your design either too big or too small relative to the drawing units.

Since mixing units is not feasible, you should draw your design separately from you map, then bring the final design into a brand new, fresh, clean metric template with an assigned coordinated system. In this new drawing, you can now geolocate the design's position, you can scale it and you can rotate it. Essentially you are making the design conform to real world conditions, not the other way around. Save this drawing as an Xref. You can now use this xref by inserting it at 0,0 and without any further scaling or rotational considerations. 

There are other considerations that play a role in georefencing objects, the three listed above are only rudimentary. For a deeper discussion with better responses, go to either the Map 3D or Civil 3D forum, where the MAPCSASSIGN function is possible.