Hello forum how are you doing? am a little bit confused I hope I will get your suggestions the problem is I used two techniques to estimate soil moisture content which are the empirical multiple regression and the change detection however, my result appeared very far from previous studies for instance the R2 for observed and estimated soil moisture content using empirical method became 0.013 the backscatter coefficient has much dependency with local incidence angle rather than the soil moisture content in my study area
@Anna2: It’s a bit unclear what kind of response you expect, because I don’t see a question in your post. Based on the information you provided, we cannot know where the deviations between your methods (and yours and other studies) come from. Objectively, possible reasons are
the studies you used for comparisons are based on different data or (spatial and temporal) scales
your field observations did not allow to create a robust regression
errors during data processing (resampling, offsets, image dates)
the two methods you compare produce different target variables
the spatial resolution of the satellite data is too coarse
vegetation or roughness introduces errors
We really cannot know. You have worked with the data for the past years, so you are the person who knows best where potential errors could have been introduced.
am sorry here is my question I predicted soil moisture content using multiple linear regression but I got low performance I mean the backscatter coefficient showed less dependency with the soil moisture content which are collected from the field
nothing wrong with that, as long as you extract these from the images of the same date. I just don’t think it is feasible to compute an R² from only 5 points. There are better ways of calculating the performance of a regression.
Maybe the images are acquired from different look directions as well?
In the end you have 60 value pairs, right? Sigma and moisture (from different dates)
yeah. Additionally, I want your suggestion also for another thing which is when I collect soil measurement I took it by considering the elevation difference of the watershed which means the samples were taken from the lower, middle, and upstream of the watershed separately so when I apply the empirical technique I got different performances in each stream, the middle stream showed better performance relatively and the middle stream is relatively flat and bare land so what do you think, please let me have your assumptions thank you so much for your time.