Units Issue: file units (inches) vs. georeferenced image units (feet)

[yasin2ray]

I am trying to georeference survey data and place it in the correct geographic space by aligning it with an orthophoto.

I have set up my base file to have the following:

Units: Architectural, Inches

Coordinate System: NAD 83, Indiana State Plane-East, Feet

The workspace: "Tool-based Geospatial" (so, I am using the Map 3D workspace of my Civil 3D 2010 program)

The orthophoto is from the state of Indiana and is in that same coordinate system: NAD 83, Indiana State Plane-East, Feet

I brought in the orthophoto using the Task Pane, following this: Data > Connect to Data, and then going to "Add Raster Image or Surface Connection"

I actually have three orthophotos, and they do align properly next to each other to show the entire area I'm working in.

THE PROBLEM:

The orthophoto is too small by a factor of 12, which tells me it is displaying as if it's in Feet, not Inches.

I thought the computer would automatically scale it correctly to my file's units when I used this "data connect" method.

The survey file units are in Decimal Feet, and when I copy and paste in the survey data, it is the same scale as the orthophotos. I do need the survey data to match the scale of the orthophoto, so that's fine... except.... both need to acknowledge the units of the base file.

I cannot simply scale up the orthophoto because then it would not be in the correct geographic location!

How do I get georeferenced images and some cad data to see my file units?

(by the way, Architectural-Inches is the standard around here and this is what the client is requesting.)

Please help!

Thanks,

Anna

[normans]

Not sure if this will help: (Had similar situation once)

Try using the units command and adjusting the Insertion scale units prior to inserting the orthophoto

[yasin2ray]

normans,

That is exactly what I had already done to set up my base file in the first place.

When I originally set up the file, I went to the Drawing Units page and set the Length Type to Architectural, and Insertion Scale to Inches.

Is it possible to bring in a georectified image that is set to Feet and have it scale properly to my Inches setting?

Or is it some strange requirement that I must set my base file to be whatever the ortho is?

anna

[wfberry]

Civil 3D is for NOT to be used with architectural anything.

Bill

[enpope]

Try to insert the ortho images using the command "mapiinsert". When you select the image it will give you an option to set the units for insertion and point density.

[yasin2ray]

enpope,

Thanks for sending the image. I tried this with my UNITS window already set to "Inches" (as I have done all along).

The images placed in the correct location, but the building that should be 315' wide is still measuring 26' wide - so there is still a units issue.

I'm left thinking the Coordinate System is what determines the units of the file, and because I'm using NAD 83_State Plane_Indiana_East_feet, I simply have to have the file set to feet...

[Cadguru42]

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@yasin2ray wrote:

enpope,

Thanks for sending the image. I tried this with my UNITS window already set to "Inches" (as I have done all along).

The images placed in the correct location, but the building that should be 315' wide is still measuring 26' wide - so there is still a units issue.

I'm left thinking the Coordinate System is what determines the units of the file, and because I'm using NAD 83_State Plane_Indiana_East_feet, I simply have to have the file set to feet...

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Just as wfberry stated, Civil 3D is not meant to be used with architectural units or any units other than feet/meters. The drawing's coordinate system is set to US survey foot and the image is US survey foot. If you want architectural units, the only way I can think of is to make a drawing with the image(s), then XREF that drawing into another drawing created using C3D as AutoCAD and the units set to inches. Even then you might have issues.

[enpope]

You can scale an ortho image once it has been inserted as long as you use 0,0 as the base point. if you scale the image at a scale factor of 12 from a base point of 0,0 the coordinates will read correctly in architectural scale.
I just tested it the make sure so I know it will work.

[KirkNoonan]

Just a quick best practices observation. It is generally a bad idea to move your drawing to the aerials. This tends to , erroneously, lead people to believe that the drawing data itself is georecitfied. It is not! It is always better to move the image to the assumed coordinate system location to match your drawing information. That is easily accomplished by keeping the imagery in an XREF. And moving the XREF to match your assumed coordinates.

Just a tip to avoid costly trouble down the road.

[yasin2ray]

Yes, KirkNoonan, the scenario you describe is correct. And I know that. What I'm doing is sort of the reverse of what you are describing. My method is correct, but I'm missing something.

Folks replying to my post seem to be skipping over some of the information in the original post.

1. My file has a coordinate system and the images are georeferenced orthophotography. That's my starting place.

2. I am following the Rubber Sheeting tutorial provided by Autodesk to place my non-georeferenced cad layers into correct geographic space by aligning them with the orthophotos.

3. My client wants the file units to be set to Architectural and Inches.

4. When my file is set to Architectural and Inches the 315 foot wide building measures 26 feet wide. (315 divided by 12 gives me the 26, so I know that there is a units issue, something relating to inches versus feet. By the way, I'm leaving out decimal points from the math I'm showing you just to simplify my point.)

I'm hoping someone experienced with coordinate systems and georeferenced files will reply...

I apologize if I'm not explaining all this very well. Perhaps there is a better title for this post.

[Cadguru42]

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@yasin2ray wrote:

Yes, KirkNoonan, the scenario you describe is correct. And I know that. What I'm doing is sort of the reverse of what you are describing. My method is correct, but I'm missing something.

Folks replying to my post seem to be skipping over some of the information in the original post.

1. My file has a coordinate system and the images are georeferenced orthophotography. That's my starting place.

2. I am following the Rubber Sheeting tutorial provided by Autodesk to place my non-georeferenced cad layers into correct geographic space by aligning them with the orthophotos.

3. My client wants the file units to be set to Architectural and Inches.

4. When my file is set to Architectural and Inches the 315 foot wide building measures 26 feet wide. (315 divided by 12 gives me the 26, so I know that there is a units issue, something relating to inches versus feet. By the way, I'm leaving out decimal points from the math I'm showing you just to simplify my point.)

I'm hoping someone experienced with coordinate systems and georeferenced files will reply...

I apologize if I'm not explaining all this very well. Perhaps there is a better title for this post.

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Did you try what I suggested and make a drawing with the orthophoto in it with the coordinate system, save it, then XREF it into the inches unit drawing?