For the first quarter ending March 31, Garmin posted a net profit of $139.8m, up from $87.5m in the year-ago quarter. Sales rose to $492m from $322m a year earlier. However this missed market expectations of sales of $499m, and shares in the company fell 4.67% to $56.60 on the Nasdaq.

Last week, Garmin’s chief European rival, TomTom NV, posted a net profit up 42% at 44m euros ($60.1m), on sales up 16% at 296m euros ($404m). During the quarter TomTom said that it shipped 1.3 million portable navigation devices, up 75% from a year ago.

Garmin on the other hand said that it shipped 1.55 million units, up 67% from the same quarter in 2006.

However it is worth pointing out that unlike TomTom, which only operates in the automotive space, Garmin’s product range spans the automotive, outdoor and fitness, marine, and aviation sectors.

Garmin’s revenue from the automotive/mobile segment, which contributes about 65% to the total revenue, increased 110% to $317m. Aviation segment revenues rose 26% to $72, but Marine revenues declined to $43m, as did outdoor/fitness, which fell to $60m in the quarter.

Looking forward, Garmin said that it expects 2007 earnings to exceed $2.70 a share on revenue of more than $2.5bn. But it warned that it continues to expect declining operating margins due to product mix and a continued transition toward mass market levels.