Laredo & Corpus Christi #6003F & 6032D 

The totmag has questionable data on many of the lines. 

Resmag was not usable for the eastern portion so it was decided to recalculate it for both parts.  
First an elevation channel was created by sampling the topographic grid for Texas and adding it 
to the radar altitude.  The data were separated into two databases for the purpose of calculating 
the IGRF.  Later, they were merged back again in the .XYZ file.  The 1965 IGRF model was originally 
used for this quad.  An IGRF65 channel was calculated using the elevation channel and median dates 
of April 29, 1974 and April 30, 1977 were used.  A new resmag channel was then calculated.  All 
values were rounded to one decimal.

The East-West lines on the west side were eliminated because the data were too noisy to work with 
and could not be filtered or leveled.

The resmag in the radiometric file was mostly dummies so the recalculated resmag was copied into 
the rad file.  The unusable mag lines eliminated in the mag file were kept in the rad file
because of the radiometric data.