Thank you for that explanation Christophe, Lastly, how do I go about launching the BandMathX application? I have otb and monteverdi installed via the Osgeo4w 64 bit installer. I only see the BandMath application. Has BandMathX been rolled out to Osgeo4W yet?
Cheers, Ginny On Apr 29, 2015 5:13 AM, "Christophe Palmann" <[email protected]> wrote: > > Basically, the purpose of radiometric correction (or optical calibration) > is to "get rid of" some parameters (like viewing angle, earth-sun > distance, and so on) that obviously affect the values of the pixels, but > that must not be taken into account for a change detection task for > instance, or supervised classification... and so on. Depending on the kind > of product to be used, radiometric correction is already performed or not; > but it is up to the user to check this. > > If the answer is no, then the user have to apply this calibration, after > having found every required parameters from the images metadata. > > Christophe. > > > > > > Le mardi 28 avril 2015 21:37:54 UTC+2, GiNN a écrit : >> >> Thank you Christophe, >> >> With your and Arnaud's explanation I grasp how pixels are handled now. I >> will run a test an give you feedback. >> >> About my expression: >> The images are WorldView2 and collected over a large period (almost two >> years). I believe they are already calibrated. I found this equation in a >> paper by digital globe to correct the solar geometry at the collection time >> (d = earth-sun distance and e = sun elevation angle), so the images will >> have more or less the same colors. So basically, a radiometric enhancement. >> >> Is this the same as an optical calibration? I took a look at the cookbook >> and the formula for TOA radiance to reflectance does look similar. >> I am new to satellite imagery and I just need the end product to be >> appealing to the eye. (I.e. similar colors) >> On Apr 28, 2015 10:46 AM, "Christophe Palmann" <[email protected]> >> wrote: >> >>> Hi Gin and Arnaud, >>> >>> Sorry for the late reply. >>> >>> As Arnaud said in his previous message, images are handled with >>> n-dimensional row vectors. >>> >>> So you can use the 'mlt' or 'dv' operators to perform multiplications >>> (divisions) between vectors and scalars; the correct expression is simply: >>> >>> 1) *im1 mlt d2 dv cose* or * im1 mlt (d2/cose)* >>> Here, im1 is similar to {pix_from_band1, pix_from_band2, >>> pix_from_band3}. I think that the second expression is faster. >>> >>> 2) the expression *im1 mlt {d2} dv {cose}* is also correct, as I >>> designed those operators to process 1d vectors as scalars (both for >>> convenience and to make the operators more robust) >>> >>> 3) finally, a solution close to the one of Arnaud is *im1 mult >>> {d2,d2,d2} div {cose,cose,cose}* >>> Here, the operators mult and div perform element-wise multiplications >>> (divisions) between vectors. But *im1 * {d2,d2,d2} / {cose,cose,cose}* >>> is not correct ! (the multiplication or the division of two row vectors >>> aren't defined, you must use mlt/dv or mult/div operators). >>> >>> Don't forget to define the constants 'd2' and 'cose' with the method >>> SetConstant if you use the filter, or just provide a txt file to the field >>> 'import context' if you use the application. You can also define 'my_e', >>> and use cos(my_e) within the above expressions (*but don't define 'e', >>> because this constant already exists in muparserx!*), nevertheless it >>> is better to evaluate cose once and for all. >>> >>> Finally, looking at your expression, you really should consider the >>> OpticalCalibration application, which will do the job faster than BandMathX >>> :-) >>> >>> Christophe. >>> >>> >>> >>> >>> Le jeudi 23 avril 2015 14:47:15 UTC+2, Arnaud Durand a écrit : >>>> >>>> Gin, >>>> >>>> Each pixel of your image is handled as a n-dimensional row vector, with >>>> n the number of bands in your image. {n1, n2, n3, ...} is the syntax of >>>> muParserX to declare row vectors that you can fill with scalars assigned by >>>> band. >>>> >>>> Hope it helps. >>>> Arnaud >>>> >>>> Le jeudi 23 avril 2015 14:10:28 UTC+2, GiNN a écrit : >>>>> >>>>> Thank Arnaud, >>>>> >>>>> And yes, d and e are scalars. In fact, they are constant for the >>>>> entire image, while the image has three bands. >>>>> >>>>> If I understand you correctly, this still counts as a vector >>>>> transformation? >>>>> On Apr 23, 2015 7:50 AM, "Arnaud Durand" < >>>>> [email protected]> wrote: >>>>> >>>>>> Hi GiNN, >>>>>> >>>>>> I'm not sure that it is possible with such a simple expression, as >>>>>> the doc said : >>>>>> >>>>>> >>>>>> >>>>>> *For instance, it is not possible to add vectors of different >>>>>> dimensions (this implies the addition of a row vector with a column >>>>>> vector),or add a scalar to a vector or a matrix, or divide two vectors, >>>>>> and >>>>>> so on...Thus, it is important to remember that a pixel of n components is >>>>>> always represented as a row vector.* >>>>>> >>>>>> However, if you know the number of bands in your image, and if d and >>>>>> e are scalars, you might try to use vector syntax in your expression like >>>>>> that : im1*{d^2,d^2,d^2,d^2}/{cos e, cos e, cos e, cos e} >>>>>> >>>>>> Arnaud >>>>>> >>>>>> Le mercredi 22 avril 2015 21:02:15 UTC+2, GiNN a écrit : >>>>>>> >>>>>>> >>>>>>> I have three-band images and I want to apply the same expression to >>>>>>> each band and get a three-bad output. >>>>>>> I am just starting with OTB and Monteverdi. Used installer on a 64 >>>>>>> bit W7 machine. >>>>>>> >>>>>>> The expression is very simple: output_pixel = (input_pixel*d^2)/cos >>>>>>> e >>>>>>> >>>>>>> I read the cookbook recipe, and concluded BandmahX is what I need. >>>>>>> But I am not sure how to formulate the expression so that the >>>>>>> application >>>>>>> goes through all pixels in all three bands. >>>>>>> >>>>>>> Any assistance is greatly appreciated. >>>>>>> >>>>>>> Gin >>>>>>> >>>>>> -- >>>>>> -- >>>>>> Check the OTB FAQ at >>>>>> http://www.orfeo-toolbox.org/FAQ.html >>>>>> >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "otb-users" group. >>>>>> To post to this group, send email to [email protected] >>>>>> To unsubscribe from this group, send email to >>>>>> [email protected] >>>>>> For more options, visit this group at >>>>>> http://groups.google.com/group/otb-users?hl=en >>>>>> --- >>>>>> You received this message because you are subscribed to a topic in >>>>>> the Google Groups "otb-users" group. >>>>>> To unsubscribe from this topic, visit >>>>>> https://groups.google.com/d/topic/otb-users/UHugkLOJEmw/unsubscribe. >>>>>> To unsubscribe from this group and all its topics, send an email to >>>>>> [email protected]. >>>>>> For more options, visit https://groups.google.com/d/optout. >>>>>> >>>>> -- >>> -- >>> Check the OTB FAQ at >>> http://www.orfeo-toolbox.org/FAQ.html >>> >>> You received this message because you are subscribed to the Google >>> Groups "otb-users" group. >>> To post to this group, send email to [email protected] >>> To unsubscribe from this group, send email to >>> [email protected] >>> For more options, visit this group at >>> http://groups.google.com/group/otb-users?hl=en >>> --- >>> You received this message because you are subscribed to a topic in the >>> Google Groups "otb-users" group. >>> To unsubscribe from this topic, visit >>> https://groups.google.com/d/topic/otb-users/UHugkLOJEmw/unsubscribe. >>> To unsubscribe from this group and all its topics, send an email to >>> [email protected]. >>> For more options, visit https://groups.google.com/d/optout. >>> >> -- > -- > Check the OTB FAQ at > http://www.orfeo-toolbox.org/FAQ.html > > You received this message because you are subscribed to the Google > Groups "otb-users" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/otb-users?hl=en > --- > You received this message because you are subscribed to a topic in the > Google Groups "otb-users" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/otb-users/UHugkLOJEmw/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- -- Check the OTB FAQ at http://www.orfeo-toolbox.org/FAQ.html You received this message because you are subscribed to the Google Groups "otb-users" group. 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