The iPad may be rising, but the iPhone still sets the tone for Apple's (NASDAQ:AAPL) results.

The smartphone accounted for $17.1 billion of Cupertino's $36 billion revenue haul this quarter, or 47.5% of total sales. That's up from 46% a year ago, so it's not like the phone's relevance is fading.

You'll see a lot of squiggly charts today that present iPhone sales in a pretty dim light. There's this ungainly bump over the holidays last year, and the last two quarters haven't even been close to that level.

But that's hardly reason to panic, though -- it's just normal seasonality. I'm not the world's biggest Apple fan, but this quarter was yet another chapter in Cupertino's long success story.

Here's the same iPhone sales data presented in a different light. The golden hill shows total iPhone sales over the trailing 12 months, with the supposedly scary quarterly graph shaded in for perspective:

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Source: Data taken from over 20 of Apple's quarterly reports.

When you smooth out the numbers this way to remove most of the seasonal effect, the chart doesn't look so scary anymore -- unless you work for Samsung, Research In Motion (NASDAQ:BBRY), or Nokia (NYSE:NOK), of course, in which case the chart looks like an approaching battalion of tanks.

Samsung is fighting back with record-level smartphone sales of its own while the Finns and Canadians should be on the endangered animals list because Apple is killing them. Former CrackBerry addicts are now embarrassed to own a RIM handset and the Lumia series of Windows phones isn't lighting up Nokia's sales like it was supposed to. But the iPhone marches on.

So you can still measure Apple by its iPhone sales, and the company still comes out smelling like grandma's freshly baked pie. There's still plenty of ground left to cover in the smartphone market, and Apple remains a leader in the space.

Fool contributor Anders Bylund has no positions in the stocks mentioned above. Check out Anders' bio and holdings, or follow him on Twitter and Google+. The Motley Fool owns shares of Apple. Motley Fool newsletter services recommend Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.