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Raster/Insert - Image from file - Scale

scale raster image

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#1 Oliver Moffatt

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Posted 15 October 2020 - 10:46 AM

I would like some help on the value to enter in the "Scale" box in the "Insert raster image" dialog.

I have an air photo raster. It is 4000 x 4000 pixels, and 500m x 500m on the ground, so each pixel is 12.5cm on the ground. I have the raster in both JPG and TIF formats, and I have a World file for each raster (JGW and TFW).

I open Insert - Image from file (or Raster - Image from file) and enter the co-ordinates of the bottom left corner of the image, and the scale set to 1.

The images are imported with the bottom left corner in the correct location. However, the JPG is displayed in my Nanocad drawing 338.6667m x 338.6667m (as indicated beside the preview in the dialog box above). The TIF imports as 853.7815m x 853.7815m.

This happens whether I use the world file, or not.

I can get the raster the right size by entering a scale of 1.4763778 (which is 500 / 338.6667) in the Scale field, or by specifying the scale on-screen. But I would like to know why it thinks the JPG should be 338.6667m wide? Why not 4000m? And why does it think the TIF should be bigger, when they are both 4000 pixels?

(In Draftsight, the image imports correctly with "Scale" set to 500, the width of the raster on the ground.)

Thanks!

#2 pguimber

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Posted 15 October 2020 - 11:05 AM

why ?

BECAUSEEEEEEE !

:D
Seriously, I don't know. I always use the Scale command with the Reference length option to size my images ...

#3 Hellen_V

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Posted 16 October 2020 - 01:13 PM

Hi Oliver,
which version of nanoCAD do you use?
Can you please send your image file to Support Center?
nanoCAD Support Team
support@nanocad.com

#4 Oliver Moffatt

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Posted 20 October 2020 - 10:51 AM

View PostHellen_V, on 16 October 2020 - 01:13 PM, said:

Hi Oliver,
which version of nanoCAD do you use?
Can you please send your image file to Support Center?
Hi Hellen_V, I am using nanoCAD version 5.0.2520.1471 – COMMERCIAL. I sent the image to the Support Centre on Friday. Have you had a chance to look at it yet?

Thanks,

Oliver





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