(This is mainly a question to Simon and Patrick but the dev-list exists so
I am using it.)

I have been trying out the retrievalAdd* functions for the systems we have
in Gottingen.  One of the most difficult bit is to figure out is how to
complete the retrieval setups without running loops around the errors being
reported.  I might be a complete idiot about this, but the documentation
and error reporting by ARTS seems far from good here.

I have identified two problems:

1)  The covmat-block size requested by the add-functions are not reported
in the documentation of said functions.

2)  The error when either retrievalDefClose or the individual retrievalAdd*
functions fail is not detailed enough to even hint at the problem, it
simply states that the covmat has the wrong size.

I have suggestions below for how I would fix it if I knew the functions
well enough.  Ignore these if you want to, but please try to address the
poor documentation and error somehow.

For the first, each individual retrievalAdd* function would have to be
addressed.  Some examples of problematic functions: jacobianAddFreqShift
reports it may be "constant in time", which means covmat _block is 1-by-1,
and jacobianAddSinefit reports "one sine and one cosine term" per
period-length, or a 2-by-2 uncorrelated covmat_block for every period
length.  These also sound like reasonable sizes, given that they both are
just used as baseline-fit for sensor phenomenon (so there is no p_grid
dependency).  However, of course they fail when you use these
covmat-block-sizes.  This means there is an error in the method
documentation.  To fix this, I suggest the increase in size of the Jacobian
matrix is written clearly in each of the jacobianAdd* descriptions.  The
same apply for their retrievalAdd* cousins, where the size of the
covmat-block should be spelled out.

The second point seems even easier to address.  If the internal check
fails, please report how.  If I see: "I was expecting the Jacobian matrix
to be 4001 x 510 and the covariance matrix to be 510 X 510.  Instead, the
covariance matrix is 498 X 498", this means that I can begin to guess at
the error.  Presently, the somewhat nonsensical "Matrix in covmat_block is
inconsistent with the retrieval grids" is used instead, which does not help
identify the cause of the problem at all.

With hope,
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