A BE25 PLT INCURRED ON IAH CLASS B AIRSPACE BECAUSE HE SELECTED THE INCORRECT MAP TYPE ON A LAPTOP GPS NAV SYS.

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WHILE APCHING THE HOUSTON CLASS B AIRSPACE FROM THE E AT 2500 FT MSL; THE CLASS B RING FLOOR/CEILING INFO WAS REFED FROM A GPS CONNECTED LAPTOP COMPUTER PROGRAM NAMED VISTA VERSION 3.90. THE INFO PROVIDED INDICATED THE FLOOR OF THE SECOND RING TO THE N OF IAH WAS 3000 FT MSL AND THE CEILING 10000 FT MSL. WHEN THE TWR CTLR INDICATED THE CORRECT CLASS B AIRSPACE PARAMETERS IN THAT LOCATION TO BE A FLOOR OF 2000 FT AND A CEILING OF 10000 FT; THE ACFT DSNDED BELOW THE CLASS B AND LANDED DWH WITHOUT INCIDENT OR REQUEST TO COMMUNICATE WITH AIRSPACE AUTHS. LATER REF TO THE HOUSTON SECTIONAL CONFIRMED THE TWR INFO AS CORRECT. AFTERTHOUGHTS: THIS ERROR WOULD NOT HAVE OCCURRED IF THE HOUSTON SECTIONAL HAD BEEN THE SELECTED MAP TYPE; RATHER THAN THE WORLD MAP USED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PLT STATED THAT THE SOFTWARE MANUFACTURER PROVIDES A GENERAL DISCLAIMER ABOUT THE ACCURACY AND VALIDITY OF THIS INFO. THE RPTR DID IN FACT CALL THE MANUFACTURER AFTER THIS INCIDENT AND WAS TOLD THAT ONLY SO MUCH INFO COULD BE PROVIDED FOR A GIVEN TASK AND THE ALGORITHM DETERMINED THE AMOUNT OF INFO NECESSARY. FOR GENERAL USE IN THIS GEOGRAPHICAL AREA; THEREFORE; SOME NON CRITICAL INFO WAS WITHHELD BECAUSE IT WAS DEEMED UNIMPORTANT. THE USER WAS ADVISED TO USE THE FULL 'OFFICIAL' OVERLAY IF MORE DETAIL IS NECESSARY. USER FELT THE LESSON TO BE LEARNED IS THAT ALL ELECTRONIC NAVAIDS ARE SUBJECT TO OPERATOR ERROR; SO USER BEWARE.