I found this reference to be moderately readable, if you follow the strategy of reading the page quickly once to get an overview, skipping the bits that are hard to understand, and then again more slowly after some formerly undefined terms are made plain. It takes about 20 minutes, but afterwards you will know way more than you wanted to about the parameters necessary to specify a map's projection. Then, read the next page for the formulas that use those parameters.

Note that at many points through the first page, they keep talking about projections of an "ellipsoid". On your first read through (when skimming) substitute the word "sphere" for "ellipsoid". Then, on your second read through, remember that the Earth is not in fact a perfect sphere and therefore you need to take into account the fact that it bulges slightly at the equator if you're going to be lining up maps with two slightly different coordinate systems.

@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/;
map{y/X_/\n /;print}map{pop@$_}@/for@/
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