The Point Blank hard specs show two values for Action Angle. The first is an "RDA" value and the second is a "CCS" value. Why the two and what does RDA stand for?

RDA stands for Rod defection analysis, and it is an offshoot of the CCS. It is based on the deflection analysis of the working length of the rod which is defined as the length of the rod in front of the reel seat. Power is is defined as the amount of weight required to deflect the blank 1/3 its working length, and the action angle is defined as the angle made by the blank when deflected 1/3 its working length. When dealing with the exact same blank, the RDA numbers will always be less than the CCS numbers, because you are analyzing a shorter section of the blank. I don’t liked the RDA because handle length varies, and it my opinion adds unknown variables to the mix. CCS analyzes all blanks the same way. However, some people prefer RDA over CCS, so that is the reason Point Blank list both analyses. Some people have tried to convert RDA numbers to CCS number but it just doesn’t work. I think most people, like myself, prefer CCS over RDA.
Norm

It's a big world out there. We try to be as bipartisan as we can.

The RDA is just the Common Cents "Big Picture" for measuring specific portions of a rod blank. Another rod builder took it, renamed it and pretended that he had come up with it. It can't be used to compare one blank against another, only portions of a blank.

It is also impossible to not to use the portion of a rod behind the reel seat. You may think it's not in play, but it is. If is wasn't, you could simply cut it off and throw it away.

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Thanks to all for the answers. Clears it up for me.

Yep, that part beyond the real seat sets the apex of the rods bend, the best example i could think of because I'm not a scientist., is a rod blank that came out years ago by Lamiglass, a fusion of titanium and carbon fiber. I told them it wouldn't work, I talked them into giving me one. I built it out to there specs, and went directly to the North fork of the Lewis River to Nail some Chinook. I wasn't there 15 minutes and landed my first one. Nobody there could believe there eyes, nobody out of 29 had caught any all day. They all wanted to know what was up with my space age rod, I told them its the latest from Lamiglass, I built it....a couple guys said they wanted one right away, I said im testing it, and I bet it will break above the titanium. On about the 6th fish, and I was horsing them, itsnapped at the titanium. The tube was not flexible, but the combo of 58 millionth modules made the front flexible.
The apex changed putting too much pressure right where the titanium met the carbon fiber.
I also proved it on accident. If yall remember when Rogue rods first brought the Carbon fiber handle into existance? Well before Bobby Loomis created them for Rogue, I had been getting tubing, that same handle material in a basket weave carbon fiber. I was putting them on Salmon rods for over a year before anyone had done it, my problem was capping them. Bobby had the money to have them made. I on the other hand worked with all kinds of stuff including black females clay to make caps. I resorted to a black uva foam fly rod but.
I kept breaking my rods, inches above the carbon fiber handle.
Guess what? That carbon fiber tabbing does not bend. Not at all. You can run over it with a truck. I gave it up for handle material..
It both cases the entire blanks arch from but to tip is the true measurement. At least the only one I pay attention too, im a cork guy for life now.
There are other factors that can affect that curve., you can actually wrapp a guide too long and too tight, affects curve, and weight, wrapping a ferrel too tight. Using too much heat during the finishing, I've held a flame under a guide I wrapped, for too long, and I only discovered it when my fly rod broke at the guide foot.