Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of ION Geophysical Corp. (NYSE: IO) popped 20% in intraday trading today after the seismic software provider reported fourth-quarter EPS that walloped the consensus estimate and announced it was awarded more than $10.7 million in a patent lawsuit.

So what: Fourth-quarter non-GAAP EPS of $0.14 was double the $0.07 consensus, helped by 31% revenue growth over the year-ago quarter. Management said it expects "the momentum that we experienced during the second half of 2010 will likely continue into 2011."

Now what: ION management did not provide revenue or earnings guidance for 2011, but expects its non-GAAP tax rate to rise from 14.5% in 2010 to 24% to 26% in 2011, and anticipates interest expense will drop from $30.8 million in 2010 to $5 million to $7 million in 2011, The lower interest expense should boost EPS by roughly $0.14 year-over-year and will likely more than offset the drag from the higher tax rate. Thus, the 2011 consensus estimate of $0.35, up from $0.16 in 2010, appears to be within reach but not a layup for a company with so many moving parts and a premium P/E ratio.

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Fool contributor Cindy Johnson does not own shares of any company named above. 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.