Georeferencing an image in AutoCAD

[jdavid10]

Hello

 

I'm trying to insert a topographic chart into AutoCAD but the problem that I have is that when the map is scanned it distorts a little bit so that its corners do not match the UTM coordinates that I have specified.

 

 

I have fixed the rotation of the scanned image using Photoshop CS3 to make the longest line of the map have 0° inclination.

 

 

Nevertheless, there is always some distortion from the scanning of the map. The map I'm using, I'm trying to insert into AutoCAD with fixed UTM coordinates.

 

 

To do this, I created a point (bottom left of the map) in AutoCAD and at "properties," I changed its (x, y) positions to match my UTM coordinates, and I created another point (top right) with the specific UTM coordinates that it should have.

 

I changed the limits of my drawing and made them to UTM limits by specifying the values.

 

But the problem I have with my image, is that after I insert it and scaled it, it's corners still don't match the points I created. It can only match one point but with the other point, there will still be some distortion; as shown below:

 

 

If you look at the map above, the point at the top right is not at the same position as the corner of the map. I cannot fix it because of the distortion of the image from the scanning process. I would have to distort the image to fix it's distortion. But I don't know how to do this in AutoCAD.

 

So my question is:

 

Is it possible to fix image distortion in AutoCAD?

Does anyone know how to correct it?

 

I measured the error between the points: it's 26.103 meters.

 

The top right point's coordinates should be (681 324 metres East, 1 009 022 m N).

 

Instead the image's point after scaling is displaced by distortion 26.103 m to the right.

 

Can this be done in AutoCAD?

 

Thank you all very much for your time viewing my post.

 

 

I'm sure this could just be done very quickly and easily. I'm probably just missing something.

 

To fix this problem I would have to resize the image but the problem is that if I try to resize my image in "properties" I can't change the width without the height changing or vice versa. AutoCAD constrains the proportions of my image.

 

I don't know how to force AutoCAD to not constrain the proportions.

 

 

I have tried resizing the image in photoshop but it won't do it to exactly 9 decimal numbers to make the other corner fit at its exact UTM location.

 

 

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PS. I just found a possible solution for my problem in another thread; but, I don't know how to apply it.

 

It says:

 

"Problem: You want to insert a raster image into a drawing, perhaps to trace over it with AutoCAD lines, circles, arcs, etc., but the aspect (width to height) ratio of the raster image isn't correct. Unfortunately, although inserting a raster image seems to be almost identical to inserting a block, you can't specify different x and y scale factors.

 

"Solution: Insert the image at the default 1:1 ratio, and then create a block that includes the image as a component of the block. Now insert the block with different x and y scale factors. Bingo! The image stretches appropriately.

Does anyone here know how to create a block that includes the image as a component of it?

Edited October 3, 2013 by jdavid10

[Organic]

Does anyone here know how to create a block that includes the image as a component of it?

 

Insert your image into AutoCad as you have done. Then make a selection window over the image, then type b for block.

[satishrajdev]

I had same problem..... I was using rubbersheet command in Autocad Map 3D to fix this prob.....

 

with rubeersheet you can Stretch perticular referance points to original coords....

[Murph_map]

Try the tools in Civil3D/Map3d to correct it, use either Rubbersheet or the align command. BTW when you scanned the paper map it does not distorts the out image, it's already "distorted" on paper. Use a scale {ruler) and measure the grids at the top and at the bottom. Now measure the grids in you dwg. The earth is round but the paper is flat.

[SLW210]

As suggest try using the Civil3D to correct it.

 

 

As far as using Photoshop, I instead use MS Paint for resizing and skewing. Just deselect "Maintain Aspect Ratio".

[jdavid10]

When I open my drawing in Civil3D, the image comes up as a rectangle with its name on it.

It's not an image anymore.

 

Just the name of it.

 

 

How can this be?

[Organic]

When I open my drawing in Civil3D, the image comes up as a rectangle with its name on it.

It's not an image anymore.

 

Just the name of it.

 

[ATTACH=CONFIG]44330[/ATTACH]

 

How can this be?

 

I've had problems like this before which were caused by the filesize of the image being too big. What is the filesize of the image you are inserting?

[Murph_map]

Make sure the lmage file is in one of the folders in your support paths.

[Emigrato]

As already mentioned by previous experts, you have several ways to fix it.

 

Here's my 3 cents:

 

1] in Autocad Map, perform the command _ADERSHEET to stretch the image at four corners.

The change is virtual, not affecting the physical raster file, therefore it works only on the current DWG.

 

2] resize physically the image in Irfanview (CTRL-R then uncheck "Preserve aspect ratio")

Leave MS Paint to kids, 'cause we're professionals, ok?

 

3] in Quantum Gis, calibrate the old image to a new one, by issueing 9 points of known UTM coordinates (4 at corners, 4 at middle frame points, 1 in the center).

The result will be a Geotiff, ready to be imported in the right place thru the Autocad Map's command _MAPIINSERT

 

P.S.

The _ALIGN command fits only to non-distorted images, so it's not suitable in your particular case.

 

[SLW210]

As already mentioned by previous experts, you have several ways to fix it.

 

Here's my 3 cents:

 

1] in Autocad Map, perform the command _ADERSHEET to stretch the image at four corners.

The change is virtual, not affecting the physical raster file, therefore it works only on the current DWG.

 

2] resize physically the image in Irfanview (CTRL-R then uncheck "Preserve aspect ratio")

Leave MS Paint to kids, 'cause we're professionals, ok?

 

3] in Quantum Gis, calibrate the old image to a new one, by issueing 9 points of known UTM coordinates (4 at corners, 4 at middle frame points, 1 in the center).

The result will be a Geotiff, ready to be imported in the right place thru the Autocad Map's command _MAPIINSERT

 

P.S.

The _ALIGN command fits only to non-distorted images, so it's not suitable in your particular case.

 

 

I am a Professional, I will now inform the entire planet that anyone using Microsoft Office tools are unprofessional.

 

YOU are very unprofessional. Unprofessional comments like that are not needed on this forum.

 

I also use Irfanview, Gimp, Photoshop, Illustrator, Inkscape and other tools.

 

Most professionals will already have MS Paint on their Windows computer.

 

I also do not see the OP mention having Quantum Gis at his disposal, another unprofessional suggestion.

 

The OP also does not have Map 3D, another unprofessional suggestion.

 

WOW, none of your suggestion seem professional.

[jdavid10]

As already mentioned by previous experts, you have several ways to fix it.

 

Here's my 3 cents:

 

1] in Autocad Map, perform the command _ADERSHEET to stretch the image at four corners.

The change is virtual, not affecting the physical raster file, therefore it works only on the current DWG.

 

2] resize physically the image in Irfanview (CTRL-R then uncheck "Preserve aspect ratio")

Leave MS Paint to kids, 'cause we're professionals, ok?

 

3] in Quantum Gis, calibrate the old image to a new one, by issueing 9 points of known UTM coordinates (4 at corners, 4 at middle frame points, 1 in the center).

The result will be a Geotiff, ready to be imported in the right place thru the Autocad Map's command _MAPIINSERT

 

P.S.

The _ALIGN command fits only to non-distorted images, so it's not suitable in your particular case.

 

 

 

I have figured out a way of solving this problem in AutoCAD; without requiring any new software.

 

It's more of a math problem than a problem with commands. And it can be done in AutoCAD. I reduced the error in the top right UTM node to 0.000001 metres.

 

Unfortunately, I can't reduce the error to a full zero.

 

However, there used to be an "OLE properties dialog box" in AutoCAD 2002 where you had an option to uncheck the "lock aspect ratio" to fix an image. I don't know if this feature still exists in the more advanced versions of AutoCAD. I've been looking for this but I haven't found it in my version of AutoCAD.

Edited July 23, 2014 by jdavid10

[jdavid10]

Make sure the lmage file is in one of the folders in your support paths.

 

Murph

 

How do you do this?

Could you please explain further?

[jdavid10]

I've had problems like this before which were caused by the filesize of the image being too big. What is the filesize of the image you are inserting?

 

The carta_detalle.jpg (detailed chart) map is a little big (7 MB).

 

But the AutoCAD drawing file will get even bigger because I have to georeference two more maps behind that one (which are even bigger).

 

I try saving my images at medium size in photoshop to reduce the size at least a little bit. Alas, I can't save as low quality ... the contour lines would have been too blurry.

Edited October 4, 2013 by jdavid10
add info

[Murph_map]

Murph

 

How do you do this?

Could you please explain further?

 

In the options, under supporting files add your folder for the image(s). Also depending on the image type you may need to add the object enabler for Raster files.

 

[GPSJane]

As already mentioned by previous experts, you have several ways to fix it.

 

Here's my 3 cents:

 

1] in Autocad Map, perform the command _ADERSHEET to stretch the image at four corners.

The change is virtual, not affecting the physical raster file, therefore it works only on the current DWG.

 

2] resize physically the image in Irfanview (CTRL-R then uncheck "Preserve aspect ratio")

Leave MS Paint to kids, 'cause we're professionals, ok?

 

3] in Quantum Gis, calibrate the old image to a new one, by issueing 9 points of known UTM coordinates (4 at corners, 4 at middle frame points, 1 in the center).

The result will be a Geotiff, ready to be imported in the right place thru the Autocad Map's command _MAPIINSERT

 

P.S.

The _ALIGN command fits only to non-distorted images, so it's not suitable in your particular case.

 

 

Thanks, #1 was super helpful. I agree about MS Paint btw. I sort of flinch every time someone mentions using it, although if it gets the job done...

[Emigrato]

You're welcome, sir.

 

About suggesting toys like Paint, in Italy we say:

"Suckers' mother is always pregnant"...

 

[Emigrato]

Mr.Worsel, since you deal scanned maps, you should definitely georeference them before you draw onto.

My suggestion:

 

1] command _IMAGE to load the scan wherever

2] command _ALIGN according to 2 known points

3] http://www.cadstudio.cz/georefimg to create the worldfile

4] close all

5] in an empty drawing, command _MAPIINSERT to import the georeferenced scan