To the OP: I had the same problem when I started diving. I did mostly shore dives, which involve a long, slow descent and a similar ascent. Plotting these dives as having been spent at the maximum depth put them WAY off the charts for the RDP, but I was using a computer, and the computer said the dives were fine. Of course, the reason for this is that the computer is doing a real-time, iterative calculation of nitrogen loading and unloading. It is not possible to do that mentally, and it would be ridiculously time-intensive to try to do it on paper or on a calculator. That's why we have dive computers!
But it is really important to understand what a computer is actually doing, because what it does really doesn't have much to do with what is going on in your body. Nobody really knows the dynamics of nitrogen in the human body, but what we know is that the models we use result in limits that reduce the incidence of DCS to a very small number. The computer doesn't know if you are cold, or if you had to swim hard against current, or if you are 100 lbs overweight. And the diver needs to know if the output from the computer is making sense; if your computer is giving you numbers that are way out of line, you should recognize that, because machines malfunction, and a malfunction in this one can be very dangerous.
I would very, very highly recommend that anyone who is interested in this stuff, or who intends to dive more than very occasionally, spent the money to acquire Mark Powell's Deco for Divers. This is a book which pulls together a very large amount of information, and presents it in a palatable (and not math-intensive) way.
As Peter said, DIR divers use intense personal monitoring of depth and time, a depth averaging approach (the limits of which have to be understood) and an ascent strategy incorporating mandatory deco for all dives. It takes time to be able to monitor and remember your depth profiles well enough to use the system, and everyone should know that the only validation of doing dive monitoring this way is the number of safe dives that are done using it.
But it is really important to understand what a computer is actually doing, because what it does really doesn't have much to do with what is going on in your body. Nobody really knows the dynamics of nitrogen in the human body, but what we know is that the models we use result in limits that reduce the incidence of DCS to a very small number. The computer doesn't know if you are cold, or if you had to swim hard against current, or if you are 100 lbs overweight. And the diver needs to know if the output from the computer is making sense; if your computer is giving you numbers that are way out of line, you should recognize that, because machines malfunction, and a malfunction in this one can be very dangerous.
I would very, very highly recommend that anyone who is interested in this stuff, or who intends to dive more than very occasionally, spent the money to acquire Mark Powell's Deco for Divers. This is a book which pulls together a very large amount of information, and presents it in a palatable (and not math-intensive) way.
As Peter said, DIR divers use intense personal monitoring of depth and time, a depth averaging approach (the limits of which have to be understood) and an ascent strategy incorporating mandatory deco for all dives. It takes time to be able to monitor and remember your depth profiles well enough to use the system, and everyone should know that the only validation of doing dive monitoring this way is the number of safe dives that are done using it.
