I am a first time satellite data user.
I am trying to plot the 2018 MODIS Aqua chlor-a mapped data, but I am running into issues.
I first plotted the data without any processing and the concentrations were negative, which is not correct. So I went to look at the user guide for the data here: https://oceancolor.gsfc.nasa.gov/docs/technical/ocean_level-3_smi_products.pdf . I noticed that I have to apply a scaling equation of Base**((Slope*l3m_data) + Intercept).
So, I tried to apply the equation. Firstly, I noticed that in the file attributes that is no Slope or Intercept information. In the pdf the Base=10. Therefore, I applied the following in MATLab: base=10; chl_scaled=base.^(chl);. When I plotted the chl_scaled it gave me values at 4x10^91 which is also impossible.
I then thought I may have read it wrong and just applied a log10(chl), but that gave me imaginary numbers...
I am currently lost as to how to solve this problem and if I am missing a step or just following the wrong instructions. Any help or guidance will be greatly appreciated.
The file that I am currently attempting to use has the following name: A20181522018181.L3m_MO_CHL_chlor_a_4km.nc. I have attached the images that I produced to show my results.
- Raw_unprocessed.png (60.64 KiB) Not viewed yet
- base_power_chl.png (43.43 KiB) Not viewed yet
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I have given it a look and that is also why I know I am doing some thing wrong.
I would also like to get the mean and sd and compare to a biogoechemical model so that is why I would like to use the data.
Just read the data as is
I realised this and I now understand that in the attributes where it says suggested_image_scaling_type=LOG is when you plot the image to use a log scale.
Baby steps to getting it right, but getting there.
Thanks for the help.