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(OP)
i have a DWG formated(autocad file) map of an area but in the map the scaling isn't mentioned .To work with an area map real scaling is very important. How can i find the real scaling of the map ?

Checking the coordinates will tell you if its in the right place in autocad world compared to the real world. The real coordinates easting and northing in NAD 83 or WGS84 aren't close to zero zero.

Easy method for scale is to just measure the distance of buildings, road widths and see if they make sense.

Other method open up google earth free program and show/find the utm coordinates of two points that are easy to identify on the map. Eyeball the spots on the map and if they are close its probably to scale.

If it's not measure the relative distance between the points on the map and the points in google earth. Figure out the scaling factor, this should be a proper factor like 1:25, 1:100; 1:250 if it was done by a person who scaled it to print on a page.

The first stage of site investigation is desktop and it informs the engineer of the anticipated subsurface conditions. By precluding the site investigation the design engineer cannot accept any responsibility for providing a safe and economical design.

In model space it should be in units that make sense. As mentioned above, measure something in model space you know the size of. Use Autocd's decimal units. If you are measuring something 20 feet wide in real life and Autocad says it measures 20 somethings then the entities were drawn in feet. If Autocad reports the length as 240 somethings then it was drawn in inches. If Autocad reports the length is 6.096 somethings then it was drawn in meters.

If you are in paper space, the viewport could be in any scale.

(OP)
Thank you Mr.IFRs but I Don't have the access to real world(the area where work is going) ... So i cant know the real length. So it is not possible for me to compare the.

There is NOTHING on the drawing that you can guess at the size of and be within a factor of 12?

If the drawing was made to millimeters vs meters, that should be discernible since it is a factor of 1000, likewise inches vs feet but that is only a factor of 12. Even millimeters vs inches is a factor of 25.4.

In the US, maps are often drawn in feet. Elsewhere it is likely to be SI units.

Is it a 3D map that shows elevations? If so, go to a side view and look at contours, if the contours are labeled you can measure from one to another.

Do the layer names offer any clues? Sometimes contour lines are on layers that include the elevation...

Given that this is a map it may follow some convention - where did you get it, who drew it?

If nothing else works, go back to the original drafter or organization, they should know.

You can type "Units" or "DDUnits" on the command line and it will tell you what the units are currently set for (but this can be changed anytime and may not reflect the data).

You can try File-Drawing Properties and see what if any information is there. Probably no help...

Suggest obtaining GPS survey of any identifiable points in the DWG. This should allow you to determine scaling and location.

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