Rotating using a line as a reference

[ducky29]

Hello there.

I got to do some georeferencing using autocad.

Im stuck at rotating the map using the red line as a reference.

I basically have to "overlap" the red line (ortho line) with the y axis of the map (x axis in cad) like the image below.

Any help is appreciated.

Drawing2.dwg

[lrm]

If I understand you correctly you want the y axis of the map (which may be skewed in AutoCAD) to be horizontal. If so,

1. Add a line on top of the map that overlays one of the vertical grid lines of the map. Use the list command to gets its angle. Tip, increase the decimal degree precision with the Units command first. You can also add an angular dimension to get the angle.

2 Use rotate to rotate the map by the desired the angle with CCW as positive.

 

From the drawing you supplied I estimate the angle to be 87.44°.

 

Do you know how to scale the map so its scale matches AutoCAD's?

[nestly]

or you could use the Reference option within the ROTATE command

 

[ducky29]

or you could use the Reference option within the ROTATE command

 

[ATTACH=CONFIG]52415[/ATTACH]

 

Thanks a lot for your help Nestly.

That solved my problem.

@Irm

I didnt try your method becouse it was not the way that we were supposed to do it.But anyways, thanks for the help.

For scaling the map I know the difference bettween 2 y coordinates in the map (x in cad), so I guess I have to make the line 1000 and Im all done(I hope im not wrong)

[nestly]

There's a [R]eference option within the SCALE command that works the same way.

 

TIP: When "eyeballing" your reference points instead of using Osnaps (which you presumably will be picking points on an image file) it's more accurate when you use Reference points that are very far away from each other. In other words. pick 78 & 84 and scale to 6000 instead of picking 78 & 79 and scaling to 1000

[ducky29]

Thanks a lot for the tip.

I guess I have to use the Scale command becouse my map is way too big and its taking forever to finish it.

[eldon]

Perhaps you could investigate the Align command. That should rotate and scale in one.

 

Also remember that Ortho sets the final angle automatically when rotating by Reference.

[danellis]

IMHO the best way to rotate and scale at the same time is to use the ALIGN command.

 

 

It was ask you to select a first source point - pick the first point on the line on your image.

The ask for a corresponding first destination point - pick the point on the CAD map that matches the start of the line.

It will then ask you to select a second source and destination point - as Nestly suggested the further apart these two are the better (if I can I always go for diagonal corners).

Just skip the option of selecting a third point and tell it that you do want to scale.

 

 

The image will be rotated and scaled to match the CAD map.

 

 

dJE

[ducky29]

I already used the rotate command.

I also tried using Align but it seem that I can't manage to rotate and scale in the same time.

I used scale command.

Clicked the line- properties

start x 50(example) end x 1050 (that means that the line is 1000 in length)

Scale - Selected the map

Base point - First point of the line- Right click on the first point -Reference

Select reference length-Clicked two points on the map (ex 39 and 40)

Specify new length- Clicked the end of the line that I created (1000 in length)

Hopefully I did it all right.

Edit:Thanks for the help everyone.

I solved all the exercise.

Edited January 15, 2015 by ducky29
solved