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1,050 post(s)
#06-Sep-19 10:40


i have a huge 32bit Integer Surface form a german state in 25mx25m Pixels.

This surface i transformed the [Height (I) to Aspect.

My next step ist to transform values from -68 to 113

to "Sommerhang" = new value "1" and the values from

-67 to 112 to "Winterhang" =new value "2".

What`s the best way to do this ?

I have MFD 8 with Surface tools and of course MFD 9.

I tried the "Trace Area" with similarity "1" in a first step with

MFD but it crashes without a command...

Thanks for the help.



9,159 post(s)
#06-Sep-19 12:44

Can you describe your next step a different way Volker?

I am confused because the ranges -68 to 113 degrees, and -67 to 112 degrees, almost exactly coincide (almost exactly overlap).

I initially thought you would like to reclassify aspects within two ranges into two new values (1 and 2), but that seems unlikely if the ranges are almost the same.


1,050 post(s)
#06-Sep-19 13:00

Hi Tim,

the result of my steps end in a Drawing where i have "Sommerhang" & "Winterhang".

I was not exactly enough, the values from

0 to 112 = Winterhang

0 to -67 = Winterhang

-68 to +/-180 = Sommerhang

113 to +/-180 = Sommerhang

Have a look at the Image in attachement.

But at the end i think i have found a workaround.

I try it again in Mfd 9: Trace Areas, Mfd ends with an error

but the Drawing was generated, so i export it to shape

(there are 2 shapes with more than 2GB is this a limit of shape ? ),

open it in Mfd 8, make a relation to

an external Table (look 2nd attachement) and at end it do a

dissolve to "Sommerhang" and "Winterhang".

The problem i think are the big data. I need a shape that

i use in another program for forest inventory.



9,159 post(s)
#06-Sep-19 13:59

Thanks, I understand now. Obvious with a picture!

So I think you have already reclassified, and the surface to be turned into areas has just values 1 and 2. (BTW in 9 this step could be done all on GPU, using multiplication and addition to avoid a conditional.)

Two possible suggestions to make it faster/complete successfully/export into smaller files:

Apply a small amount of smoothing to the surface before or after calculating aspect. Aspect tends to be over-sensitive and the result is often noisy. This would also reduce output file size. (You may already have done this.)

Try creating contours rather than tracing areas? The result would again be smoother (though no less accurate, realistically speaking, since sunlight does not produce jagged edges!).


1,050 post(s)
#07-Sep-19 19:28

Thank you much.

I will try this 😃

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