Having trouble scaling an xref image in autocad

[dth22]

So I am trying to make a site map for a building my buddy just bought. I found a lot map on the city's online database, cropped it to the area of his lot's block, and saved the image file. I then opened up a new autocad file and xreferenced the image. I know the front of his building on the site is 45' so I made a polyline that is the length of the facade over top of my xref image. Then I selected the image, used the scale command, selected one side of my polyline as a basepoint, used reference, entered 45' as the known length, and then selected the other end of the polyline. My image scaled but is now incredibly small. So small that the entine site isn't even 1". I keep trying but I'm doing something wrong somewhere. Can someone help me out?

[Guest AARi]

[c][/c]

Read carefully the CommandLine

A)Press scale command>Select object > pick up the image to be scaled and INTRO.

the originally xref-image on the left has a 18.2 size to become to a 41

B) Precise scale base : > point “A” 

C) Precise scale factor [Copy or Reference]: Select “R”

D) Now precise Reference-Length: So pick points “A to B”, this is the original length [18.2 in the sample]

E) Finally precise New length or [Point]: so pick the point “C”

Now the façade is scaled to 41

[CyberAngel]

I do the same thing on a regular basis. Images are sized according to pixels, not distances, so you have to scale them up by a ridiculous amount.

 

Start by inserting the image at a ridiculous scale, but a round number, say 1000. Measure the distance you know as it appears in the image. For instance, the front of your friend's building may measure 32.4 feet. Take that number and divide it into the actual distance, in this case 45/32.4 = 1.3889. Change the image scale from 1000 to 1000 * 1.3889 = 1389 (that's why it helps to use a round number). Verify that the distance in the image matches the actual distance. Proceed with whatever you were going to do.

 

AARi's method works too and lets AutoCAD do the math for you.