Re: [Qgis-user] NoData in RGB Imagery

(WhereGroup) Sent: 14 January 2022 09:39 To: Richard McDonnell ; Qgis Users List Subject: Re: [Qgis-user] NoData in RGB Imagery Hey Richard, do you have different NODATA pixels between the three bands (R, G, B) or is it the same? If there are no differences then you can use an additional

Re: [Qgis-user] NoData in RGB Imagery

Hey Richard, do you have different NODATA pixels between the three bands (R, G, B) or is it the same? If there are no differences then you can use an additional channel as mask. I would suggest you store your imagery in GeoTIFF with an "internal mask". Even posted a nice example of this in ht

[Qgis-user] NoData in RGB Imagery

Hi all, I have a general GIS query and am hoping I can get some insight from the community. It relates to how we deal with pixels with no data in RGB Imagery. It seems to be typical to produce RGB imagery as 8bit with pixel values between 0 and 255, with either 0 or 255 being used as the NoDATA

[Qgis-user] Nodata pixels in the raster calculator

It appears to me that the raster calculator treats a nodata pixel the same as any other pixel, performing the requested operation on the nodata pixel as if it were a valid value. In addition, it appears that there is no way to create an output raster that has a nodata val

Re: [Qgis-user] nodata and raster calc

Hi, In 99 % of what I do, treating nodata in any other way than a data mask would be severely detrimental to my results. This would include OR and AND. (The scientific equivalence of “Do you want it eat pizza or ‘I don’t know’? or Do you want to eat pizza or nothing?” are two different valid qu

Re: [Qgis-user] nodata and raster calc

In fact I would always expect nodata. nodata is what it says: no data. How can one calculate or generate new values with one unknown term. Especially in the case of boolean. Lets take an example from real life. You have the information of wet or not wet area. In the case of wet you have to reduc

Re: [Qgis-user] nodata and raster calc

nodata + 1 = nodata nodata * 1 = nodata nodata AND 1 = nodata nodata OR 1 = 1 nodata + 0 = nodata nodata * 0 = nodata nodata AND 0 = 0 nodata OR 0 = nodata Håvard On 11. feb. 2019 09:47, st_kie...@web.de wrote: I absolutely agree. For the Discussion. nodata is a valuable information, and is g

Re: [Qgis-user] nodata and raster calc

I absolutely agree. For the Discussion. nodata is a valuable information, and is getting lost when dealing as desired value. Although the OR part needs more Discussion. For consistency that has to be nodata as well. What about nodata OR 0? In my opinion nodata always needs a discrete treatment

Re: [Qgis-user] nodata and raster calc

On 11/02/2019 10:42, Tim Sutton wrote: Hi On 11 Feb 2019, at 10:38, Havard Tveite wrote: nodata + 1 = nodata nodata * 1 = nodata nodata AND 1 = nodata

Re: [Qgis-user] nodata and raster calc

I've thought that AND and OR are boolean operators and will produce TRUE (1) or FALSE (0) nodata + 1 = nodata nodata * 1 = nodata nodata AND 1 = 0 (false) nodata OR 1 = 1 (true) Mit freundlichen Grüßen Stefan Giese Projektleiter/Consultant ***

Re: [Qgis-user] nodata and raster calc

Hi > On 11 Feb 2019, at 10:38, Havard Tveite wrote: > > nodata + 1 = nodata > nodata * 1 = nodata > nodata AND 1 = nodata > nodata OR 1 = 1 Hmm yes, the OR case should return one! Regards Tim --- Tim Sutton t...@qgis.org ___ Qgis-user

Re: [Qgis-user] nodata and raster calc

nodata + 1 = nodata nodata * 1 = nodata nodata AND 1 = nodata nodata OR 1 = 1 Håvard On 11. feb. 2019 03:11, Nyall Dawson wrote: Hey all, I'm seeking some feedback on whether our current handling of nodata pixels in the raster calculator is correct, or (my suspicion) annoying and limiting. Cu

Re: [Qgis-user] nodata and raster calc

On 2/10/2019 7:11 PM, Nyall Dawson wrote: > Hey all, > > I'm seeking some feedback on whether our current handling of nodata > pixels in the raster calculator is correct, or (my suspicion) annoying > and limiting. > > Currently, we treat nodata pixels the same as a "NULL" value in SQL -- > so ANY f

[Qgis-user] nodata and raster calc

Hey all, I'm seeking some feedback on whether our current handling of nodata pixels in the raster calculator is correct, or (my suspicion) annoying and limiting. Currently, we treat nodata pixels the same as a "NULL" value in SQL -- so ANY function or operation with nodata as an input results in

Re: [Qgis-user] Nodata and raster calculator

Hi Jfprieur, Yes, Nicolas is right. In my input data: 0 defined as the No data value. Then getting the mask as you want. Will try similar rage dataset again -- View this message in context: http://osgeo-org.1560.x6.nabble.com/Nodata-and-raster-calculator-tp5182962p5184315.html Sent from the Q

Re: [Qgis-user] Nodata and raster calculator

I will check what Nicolas have mentioned (is the 0 as assigned as nodal value in input raster), that dataset is at home and will write you tomorrow again. BTW, Jfprieur can share the small clip of your data set I could give a try !!! -- View this message in context: http://osgeo-org.1560.x6.n

Re: [Qgis-user] Nodata and raster calculator

Salut JF, Not sure... perhaps 0 is her no data value in her original DEM... just a guess. This could help... http://gis.stackexchange.com/questions/33764/how-to-change-null-values-raster-values-to-0-in-qgis http://gis.stackexchange.com/questions/81640/how-to-set-all-pixels-with-value-0-to-nodata

Re: [Qgis-user] Nodata and raster calculator

Merci Nicolas ;) I understand your explanation but why does Kavinda's example set the result to the rasters nodata value eg. he does not have to set the nodata value to 0 manually. Seems to be using float as well. I must not be seeing something obvious. Thanks for your patience. -- View this me

Re: [Qgis-user] Nodata and raster calculator

Salut JF, What you are seeing is normal behavior. The "3.xxx e-38" is, like you say, the normal float default. So your question is about the 0. When you create and expression like ("Montmorency_DSM_NN5m_17x17_mean11@1" <= -0.005 OR Montmorency_DSM_NN5m_17x17_mean11@1" >= -0.005 ), this gives

Re: [Qgis-user] Nodata and raster calculator

Still get the same error, the masked value is set to 0 while the nodata for the new raster is the usual float default of 3.xxx e-38 Starting to wonder if it is not something stupid like the fact that the french decimal separator is a comma instead of a period or something like that. I tried multip

Re: [Qgis-user] Nodata and raster calculator

Yes, I understand, seems to be the only difference with what I tried to do, that is why I picked up on it. But since he gets the same result even without, I am even more confused. I will try to replicate and report back, away from the desk today unfortunately. -- View this message in context: h

Re: [Qgis-user] Nodata and raster calculator

That multiplication was to get meters to feet (3.28). Nicolas Cadieux M.Sc. Les Entreprises Archéotec inc.  8548, rue Saint-Denis Montréal H2P 2H2 Téléphone: 514.381.5112  Fax: 514.381.4995 Le 2015-01-22 11:30, "jfprieur [via OSGeo.org]" a écrit :

Re: [Qgis-user] Nodata and raster calculator

Thank you for this, not sure if I have time today but I will try your example (only difference I can see is that you multiply the result by a float (3.28) whereas I do not have that multiplication) and get back to the list. -- View this message in context: http://osgeo-org.1560.x6.nabble.com/No

Re: [Qgis-user] Nodata and raster calculator

Hi, even I got the no data for mask area without float multiplication. -- View this message in context: http://osgeo-org.1560.x6.nabble.com/Nodata-and-raster-calculator-tp5182962p5183194.html Sent from the Quantum GIS - User mailing list archive at Nabble.com. _

Re: [Qgis-user] Nodata and raster calculator

It worked out well for my case, getting the nodata for masked area (if I understood the question correctly) See the screenshots here https://docs.google.com/document/d/1agCT2_jLei2vR68vM5DJOvWNDtYV1UrLdoChXgTGHeg/edit?usp=sharing -- View this message in context: http://osgeo-org.1560.x6.nabbl

Re: [Qgis-user] Nodata and raster calculator

I also have been doing it manually. There should be an option in the Qgis calculator for that but I did not find it. Hopefully, someone will both teach us something new if the option exists... Nicolas Cadieux M.Sc. Les Entreprises Archéotec inc.  8548, rue Saint-Denis Montréal H2P 2H2 Téléph

[Qgis-user] Nodata and raster calculator

Hello, I am using QGIS 2.6.1 raster calculator to mask a curvature raster to exclude a range of values. I am following the instructions at http://docs.qgis.org/2.6/en/docs/user_manual/working_with_raster/raster_calculator.html and am getting the proper output. My question is: Is it possible to

Re: [Qgis-user] NoData

Bernd and Matt: thank you very much for answering. still the ideas are quite confused but your help gave a chance for understanding ;) any further suggestion from other users is well accepted! all the best, Nic Date: Wed, 15 Oct 2014 12:24:09 +1100 Subject: Re: [Qgis-user] NoData From

Re: [Qgis-user] NoData

I can contribute a couple of things from my experience with some of these. 1. there are some gotchas with using NULL (in vector files) is that the result of X+NULL or X concatenate NULL, effectively any operation using NULL the result is NULL. This is expected/deliberate. I've only come across Nan

Re: [Qgis-user] NoData

This post seemes to have drowned, so I dare to bump it, hoping that some less confused people like me might anwser to it. I'm using QGIS for years now, but I never figured out how that stuff is supposed to work. One of the reasons why I try to do a lot of stuff now in R is that NA is NA ! A

[Qgis-user] NoData

hi all! please, is there someone who could explain properly all the "NoData topic"? I mean: 1. differences in setting negative values (-999, -, -3.40282e +35, etc) VS NoData (Nan, NoData, NULL) 2. how QGIS handles it 3. "best practices" or good hints for managing them sorry but I've quite a

Re: [Qgis-user] nodata color in rasters

>"Nodata has a value: you can use a custom palette and asign a colour to that value." I suppose the Nodata value is the value automatically set as transparent under the tab "Transparency" in the raster's "Layer Properties". In my case, this value is: -3.40282e+38. (other possible values? 25

Re: [Qgis-user] nodata color in rasters

-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Il 09/03/2014 21:23, Carol Kraemer ha scritto: > Antonio, > > I also don't see a way of making nodata a different color, however, there may > be a > way to trick it by redefining nodata to be a pixel value then using*Singleband > Psuedocolors* under

[Qgis-user] nodata color in rasters

Someone knows if there is a way to set a color for nodata values in rasters ? Actually in the GUI I didn't find it and nodata values are always displayed as transparent. Antonio Valanzano ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.

Re: [Qgis-user] NoData on GRASS Raster

>> In GRASS maps itself the NoData, i.e. null(), cells are left transparet. >> In QGis these are shown with the colour of the most inferior class. >> How can I get them to be transparent? > any idea where I should look at? I files a bug here: http://hub.qgis.org/issues/7516 __

Re: [Qgis-user] NoData on GRASS Raster

On Thu, Apr 4, 2013 at 1:42 PM, Timmie wrote: > Hello, > I have loaded a GRASS raster directly by opening the mapset. > > In GRASS maps itself the NoData, i.e. null(), cells are left transparet. > > In QGis these are shown with the colour of the most inferior class. No data values should be trans

Re: [Qgis-user] NoData on GRASS Raster

> In GRASS maps itself the NoData, i.e. null(), cells are left transparet. > In QGis these are shown with the colour of the most inferior class. > How can I get them to be transparent? any idea where I should look at? Thanks. ___ Qgis-user mailing list

[Qgis-user] NoData on GRASS Raster

Hello, I have loaded a GRASS raster directly by opening the mapset. In GRASS maps itself the NoData, i.e. null(), cells are left transparet. In QGis these are shown with the colour of the most inferior class. How can I get them to be transparent? In the transparency settings (next tab in proper