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Ok,<br>
if I apply this approach<br>
<br>
(“m@1" < 238 AND “m@1" > 213 AND “m@2" < 123 AND “m@2" >
98 AND “m@3" < 125 AND “m@3” > 99)<br>
<br>
it is perfectly working either. Except that QGis is not cleanly
extrapolating the legend!<br>
After that I applied pseudocolor and 1 channel with min=0.1 and
max=1 and do classify (only 1 class!). Et Voila, there is indeed the
desired value in that result layer.<br>
<br>
cheers<br>
<br>
Stefan<br>
<br>
<div class="moz-cite-prefix">Am 31.07.2015 um 15:37 schrieb Stefan
Kiefer:<br>
</div>
<blockquote cite="mid:55BB7A1C.9090705@web.de" type="cite">
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Hi Nick,<br>
back to office I was eager to try by myself. Actually it seems
that the result of multiple AND or multiple layers - I didn't
check this by now - results in values slightly lower 1 (e.g.
0.9995 in my case). And therefore maybe rounded to "0". What I
have done is the folowing:<br>
<br>
<meta name="qrichtext" content="1">
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;"><!--StartFragment-->(1/("pm2-5-europe-2001-2010@1">240
AND
"pm2-5-europe-2001-2010@1"<250))*(1/("pm2-5-europe-2001-2010@2">139
AND "pm2-5-europe-2001-2010@2"<145)) *
(1/("pm2-5-europe-2001-2010@3">80 AND
"pm2-5-europe-2001-2010@3"<85))<br>
<br>
</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">which
results in a perfektly fitting mask of my pseudo demand.<br>
</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">Mayby
you could verfy this with your data<br>
</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br>
cheers<br>
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Stefan<br>
<br>
<div class="moz-cite-prefix">Am 31.07.2015 um 08:48 schrieb Stefan
Kiefer:<br>
</div>
<blockquote
cite="mid:1309030743.598358.1438325334696.JavaMail.open-xchange@omgreatgod.store"
type="cite">
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charset=utf-8">
<div>
<div>Hi Nick,</div>
<div>you are absolutely right. My thought was, that you get A
layer with distinct values to identify the road. For a mask
you are on the right way, and I either don't understand the
behaviour except that you operate over three layers, which
of course should work.</div>
<div>Have you tryed to generate a composit of the three layers
and mask the single values resulting for road structures?
(it's more or less what I expected from my first approach.)</div>
<div> </div>
<div>cheers</div>
<div> </div>
<div>Stefan</div>
<br>
> Nick Papadonis <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:npapadonis@gmail.com"><npapadonis@gmail.com></a>
hat am 31. Juli 2015 um 08:31 geschrieben:<br>
> <br>
> <br>
> Hi Stefan,<br>
> <br>
> It’s my understanding black has a value of 0 in the
resulting layer.<br>
> <br>
> I tried this and it results in similar image to step (a)
and also includes other colors at lower intensities mixed in
with the red. The red has the highest intensity in the
greyscale. I’m looking to create a binary image with just the
colors of red in the palette I choose and using this trace
vectors over the paths.<br>
> <br>
> Thanks,<br>
> Nick<br>
> <br>
> > On Jul 31, 2015, at 2:04 AM, Stefan Kiefer <a
moz-do-not-send="true" class="moz-txt-link-rfc2396E"
href="mailto:st_kiefer@web.de"><st_kiefer@web.de></a>
wrote:<br>
> > <br>
> > Hi Nick,<br>
> > I believe it is black bcause you always get a value
of "1". Unfortunately I can not verify this, because I have no
QGis by this moment. Most propably you wanted to calculate:<br>
> > <br>
> > (“m@1" < 238 AND “m@1" > 213 AND “m@2" <
123 AND “m@2" > 98 AND “m@3" < 125 AND “m@3” > 99) *
((“m@1" < 238 AND “m@1" > 210) * "m@1") + ((“m@2" <
123 AND “m@2" > 94) * “m@2") + ((“m@3" < 130 AND “m@3"
> 98) *“m@3"))<br>
> > <br>
> > cheers<br>
> > <br>
> > Stefan<br>
> > <br>
> > > Nick Papadonis <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:npapadonis@gmail.com"><npapadonis@gmail.com></a>
hat am 31. Juli 2015 um 07:49 geschrieben:<br>
> > > <br>
> > > <br>
> > > One more comment. The resulting layer histogram
is showing the pixel range spread over frequency in floating
point values. Is the raster calculator performing floating
point math with potential rounding error?<br>
> > > <br>
> > > I found it also interesting that the following
expression resulted in a layer, which when inspected for band
values, has integer values of 2 and 3. 3 being the value I
want for the red route.<br>
> > > <br>
> > > a) ((“m@1" < 238 AND “m@1" > 210) * 1) +
((“m@2" < 123 AND “m@2" > 94) * 1) + ((“m@3" < 130
AND “m@3" > 98) * 1) <br>
> > > <br>
> > > I then change the expression to only use values
2 and greater and this shows properly:<br>
> > > b) ((“m@1" < 238 AND “m@1" > 210) * 1) +
((“m@2" < 123 AND “m@2" > 94) * 1) + ((“m@3" < 130
AND “m@3" > 98) * 1) > 2<br>
> > > <br>
> > > I then changed the expression to ensure all
three values are obtained and it results in a black image of
0’s. I was expecting only the red route to appear as it
resulted in value of 3 in step (a). <br>
> > > <br>
> > > ((“m@1" < 238 AND “m@1" > 210) * 1) +
((“m@2" < 123 AND “m@2" > 94) * 1) + ((“m@3" < 130
AND “m@3" > 98) * 1) > 2.1<br>
> > > ((“m@1" < 238 AND “m@1" > 210) * 1) +
((“m@2" < 123 AND “m@2" > 94) * 1) + ((“m@3" < 130
AND “m@3" > 98) * 1) >= 3<br>
> > > <br>
> > > I’m wondering how much testing the Raster
Calculator has gone through and if there is a possible bug
here. Perhaps something to do with floating point?<br>
> > > <br>
> > > Thanks again<br>
> > > <br>
> > > > On Jul 31, 2015, at 12:39 AM, Nick
Papadonis <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:npapadonis@gmail.com"><npapadonis@gmail.com></a>
wrote:<br>
> > > > <br>
> > > > Folks,<br>
> > > > <br>
> > > > I’m using QGIS 10.1. The following
expressions result in a black raster of 0’s, when I expected
only red pixels to appears in the binary image indicating
routes on a map:<br>
> > > > <br>
> > > > a) (“m@1" < 238 AND “m@1" > 213 AND
“m@2" < 123 AND “m@2" > 98 AND “m@3" < 125 AND “m@3”
> 99) * 1<br>
> > > > b) ((“m@1" < 238 AND “m@1" > 210) *
1) * ((“m@2" < 123 AND “m@2" > 94) * 1) * ((“m@3" <
130 AND “m@3" > 98) * 1)<br>
> > > > <br>
> > > > I then tried the following individual
expressions for each band as separate steps (sanity check) and
they work to cover the pixels in range:<br>
> > > > c) (“m@1" < 238 AND “m@1" > 213) * 1<br>
> > > > d) (“m@2" < 123 AND “m@2" > 98) * 1<br>
> > > > e) (“m@3" < 125 AND “m@3” > 99) * 1<br>
> > > > <br>
> > > > I then tried the following expression
which appears to create a proper greyscale image focusing on
the red pixels. I replaced the multiplication with addition to
see what was happening:<br>
> > > > f) ((“m@1" < 238 AND “m@1" > 210) *
1) + ((“m@2" < 123 AND “m@2" > 94) * 1) + ((“m@3" <
130 AND “m@3" > 98) * 1)<br>
> > > > <br>
> > > > The resulting raster has a Min = 0 and Max
= 1.998. I was expecting it to be Min = 0 and Max = 3. The
value of 3 would indicate all 3 bands were positive on color
match. I then go to the layer properties and load calculate
min/max again and it is Min = 0 and Max = 3. I tried to change
the min/max settings on they layer and these settings will not
stay set. The layer goes back to Max = 1.998. What’s even more
odd is the max being a floating point number. I suspect that
may be part of the issue. Anyone know why this is the case for
integer band values? Has anyone successfully used the Raster
Calculator to perform this sort of work before?<br>
> > > > <br>
> > > > Thanks again,<br>
> > > > Nick<br>
> > > <br>
> > > _______________________________________________<br>
> > > Qgis-user mailing list<br>
> > > <a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a><br>
> > > <a moz-do-not-send="true"
class="moz-txt-link-freetext"
href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br>
> </div>
<br>
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