Earthdata Forum

Dear @gnwiii

1. OK. So, I should use l3mapgen for visualizing my result. Am I right?

2. you mentioned that I can get not only the averages, but other useful statistics but when I use ‘l3bin’, there is not any option in it for chosing statistics like below items that you mentioned them (look at image1):

            avg       average value (default)
            stdev     standard deviation
            var       variance
            nobs      number of observations in the bin
            nscenes   number of contributing scenes
            obs_time  average observation time (TAI93)
            bin_num   bin ID number

How can I calculate them?
Thanks for helping me (sorry for late responses because I am in a conference)

Cheers

1. Yes, use l3mapgen to generate mapped files in formats that can be viewed in SeaDAS 7 and many other visualization tools.

2.  You can use l3mapgen to generate mapped files that include your desired statistics.   One caveat: the binned files store sums and sums of squares and compute variances with the naive one-pass algorithm.   For data that have unfortunate scaling this algorithm introduces large cancellation errors.  Most standard products in SeaDAS avoid this problem, but some non-standard products require a carefull choice of scale to minimize cancellation error.

Hi Marjan, you are misunderstanding the post by gnwiii.  You use l3mapgen not l3bin to view the statistics which he mentioned.

For instance from command line:
l3mapgen ifile=A2010283.L3b_DAY_OC product=chlor_a,chlor_a:stdev

The above command will produce a mapped file with both the chlor_a and chlor_a_stdev rasters.  You use the notation of {product:stat}

It looks like you are just using the GUI.  I just tested this in the GUI and there is an unfortunate bug.  However, here is the workaround.

1. Open l3mapgen GUI
2. Select the ifile (for example: A2010283.L3m_DAY)
3. Specify the product (for example: chlor_a,chlor_a:stdev) and any other parameters
5. Click on the ofile textfield and specify a valid file name  (for example: A2010283.L3b_DAY)
6. Press Run

Note the bug is that the GUI tries to auto-name the ofile by tagging your product and resolution onto the name resulting in a bogus name in this particular case: A2010283.L3m_DAY_chlor_a,chlor_a:stdev_9km.nc

The bug will be fixed in a future release.

Danny

Dear Danny
I back again on this topic after conference now and tried to continue but I got a strange error.
I tried to open ‘A2018021.L3b_DAY_CHL.nc’ and used file...open but I got below error. Why?

‘No appratiate reader found………………………………..’

Marjan

The bin (L3b) file format is not a raster format and must be mapped to a raster for display.  An early version of SeaDAS 7 did the mapping on the fly but it was unacceptably slow and required significant system resources to do, so we removed it.  To display the L3b data, you will need to first map the data with l3mapgen.  If it is a standard file that we produce, you could grab the mapped file we created A2018021.L3m_DAY_CHL_chlor_a_4km.nc

Sean