AN EMB145 EXPERIENCED DUAL GPS FAILURES WHILE FLYING AN RNAV DEP WITHOUT FLT STATION ANNUNCIATION.

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RNAV DEP DEV WE WERE ASSIGNED RWY 17R ON THE AKUNA TWO RNAV DEP FROM DFW. DURING TAXI; THE PROPER RWY ENTRY AND ALL WAYPOINT FIXES WERE VERIFIED ON OUR FMS DISPLAYS. WE TOOK OFF AND IN THE INITIAL CLB WERE IN FMS-NAV MODE. TWR QUICKLY HANDED US OFF TO DEP CTL. AT 1080 FT; THE FMS COMMANDED THE L TURN TO THE FIRST FIX; NAVYE. AS THE ACFT BEGAN TURNING; MY GUT FEELING WAS SOMETHING WAS WRONG AS THE TURN SEEMED EXCESSIVE. I QUICKLY CHKED THE RNAV SID AND THE FMS DISPLAY AND ALL WERE CORRECT. AT THIS TIME; DEP CTL SAW THE FLT PATH DEV AND GAVE US A TURN BACK TO THE R. THE NEXT THING WE OBSERVED ON BOTH FMS DISPLAYS WAS A FLASHING YELLOW POS SYMBOL. UPON SELECTING THE MESSAGE PAGE; THE DISPLAYS SHOWED 'POSITION CORRECTING' MESSAGES. WHEN THINGS FINALLY SETTLED DOWN; WE INVESTIGATED THE FMS FURTHER. ON PAGE TWO OF THE DATA PAGE SELECTION WE FOUND DISPLAYED IN RED BOTH GPS 1 FAIL AND GPS 2 FAIL. WE NEED TO HAVE AN IMMEDIATE ALERT TO THIS FAILURE POSSIBILITY WHICH WAS TOTALLY ABSENT IN THIS EVENT. THE ALERT SHOULD BE EITHER AURAL OR BE PROMINENTLY DISPLAYED ON THE PFDS AND MFDS. AN ALERT DISPLAYED ON THE FMS IS NOT IMMEDIATELY NOTICEABLE AT THIS CRITICAL PHASE OF FLT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT UNLESS AN FMS PAGE SEARCH HAD BEEN CONDUCTED THE CREW WOULD NEVER HAVE KNOWN THE SOURCE OF THE PROBLEM. NO EICAS OR PFD ANNUNCIATION IS PROVIDED AND THE RPTR BELIEVES THAT THIS CONDITION IS PRESENT ON ALL EMB145'S IN HIS ACR FLEET.SUPPLEMENTAL INFO FROM ACN 677393: BOTH THE CAPT AND I SHOULD HAVE CAUGHT THE TURN SOONER; BUT WE HAVE BECOME VERY COMPLACENT WITH THE LEVEL OF NAVIGATION WE HAVE NOW; WE MAY BE TRUSTING IT TOO MUCH. WE NEED TO REMEMBER THAT THINGS ARE STILL GOING TO BREAK AND WE HAVE TO KNOW WHERE WE ARE SUPPOSED TO BE AT ALL TIMES. THE WORKLOAD DURING THE TKOF PHASE IS VERY HVY AND WE NEED TO BE EXTRA AWARE OF WHAT OUR ACFT IS DOING.