TomTom, the GPS device maker, has raised its offer for digital mapping service Tele Atlas to $4.22 billion. This is a substantial rise over rival Garmin's prior bid of $3.3 billion. That offer topped a prior one by TomTom for $2.5 billion. The market thinks the purchase price will be driven higher as Tele Atlas's stock price is trading higher than even the latest offer. TomTom has purchased a 28.3 percent stake in Tele Atlas already on the public market. Garmin owns a little over 5 percent of the company.