Hi Eugenio, I've opened a ticket in QGIS bug tracker, to try to identify the source of the problem:
https://issues.qgis.org/issues/16646 Please see the recent findings and give your feedback there. Thanks! Best regards, Pedro Venâncio 2017-06-01 8:43 GMT+01:00 Eugenio Trumpy <[email protected]>: > Hi Pedro, > > > I did the same for 5 pixels in the test raster I shared with you yesterday. > > The different seems to be a little bit greater. > > See the attached sheet. > > > I don't know if the version of saga, 2.3.1 the mine vs 2.3.2 the yours > could generate this error, > > or if the problem is in qgis process model. > > > E. > > > > > > > ------------------------------ > *Da:* Pedro Venâncio <[email protected]> > *Inviato:* mercoledì 31 maggio 2017 22:16 > *A:* Eugenio Trumpy > *Cc:* qgis-user; qgis-developer > *Oggetto:* Re: [Qgis-user] Wrong result with Saga Raster calculator > > Hi Eugenio, > > I've created a sample processing model (attached), that works ok, except a > small error in the result (decimals). > > For instance: > > *Raster* *ID* *Pixel value* > Z_top_res a 1202,03510276 > t_top_res b 53,6123428345 > topo c1 -182,584899902 > SAGA Result 1 c 15,1783676147 > SAGA Result 2 d 31,9437332153 *Diff* > Expected Result 1 > 15,1783679504 0,000000335741 > Expected Result 2 > 31,9740872222 0,0303540069 > *Formula* > 1 ifelse(c1>0,-(0.0065*c1-16),(0.0045*c1+16)) > 2 ifelse(a<500,0,((b-c)/a)*1000) > Using SAGA GUI there is no error. > > Could this be because of some roundings in the input / output? (I'm > sending for the developer's list also). > > Thanks! > > Best regards, > Pedro Venâncio > > > > 2017-05-31 10:56 GMT+01:00 Eugenio Trumpy <[email protected]>: > >> >> Hi Pedro, >> >> thank you very much to have tested the computation with my test data! >> You are right, I checked again the computation and actually it works. >> >> However, I was using Saga raster calculation in a processing modeler, and >> one of the layer I share with you >> is the resulting from a previous computation. >> >> In other word the raster layer c=temp_recal.tif comes from a previous >> computation (raster calculator): >> ifelse(a>0,-(0.0065*a-16),(0.0045*a+16)) >> where a is the layer attached, and hence c of the previous formula is >> the resulting of this first computation. >> >> E. >> >> ------------------------------ >> *Da:* Pedro Venâncio <[email protected]> >> *Inviato:* mercoledì 31 maggio 2017 11:37 >> *A:* frippe12573; qgis-user >> *Oggetto:* Re: [Qgis-user] Wrong result with Saga Raster calculator >> >> Hi Eugenio, >> >> The result with SAGA Raster Calculator seems ok here, on QGIS 2.18.9, >> SAGA 2.3.2, both from OSGeo4W64 (result attached). >> >> Z_top_res.tif have values from 724.403 to 1423.553, and so, the first >> condition is never true. Then, it always make ((b-c)/a)*1000, and the >> result seems ok to me. >> >> >> Pedro >> >> >> >> 2017-05-31 10:19 GMT+01:00 frippe12573 <[email protected]>: >> >>> Hi Paolo, >>> >>> the raster have the same size and origin. >>> The pixels are precisely overlapped. >>> >>> I tried also r.mapcalc, but I got a worst result. >>> Here the output of the log: >>> https://pastebin.com/jNyyzHgf >>> >>> E. >>> >>> >>> >>> -- >>> View this message in context: http://osgeo-org.1560.x6.nabbl >>> e.com/Wrong-result-with-Saga-Raster-calculator-tp5322429p5322442.html >>> Sent from the QGIS - User mailing list archive at Nabble.com. >>> _______________________________________________ >>> Qgis-user mailing list >>> [email protected] >>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> >> >> >
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