C210 pilot had incursion of sea class B airspace.

Attributes
ACN	476760
Time
Date	200006
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : bfi.airport
State Reference	WA
Altitude	msl bound lower : 1700 msl bound upper : 2200
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : s46.tracon tower : bfi.tower
Operator	general aviation : personal
Make Model Name	Cessna Aircraft Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	climbout : intermediate altitude
Flight Plan	VFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Experience	flight time last 90 days : 60 flight time total : 600 flight time type : 50
ASRS Report	476760
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : radar
Events
Anomaly	airspace violation : entry non adherence : published procedure non adherence : far
Independent Detector	other controllera
Resolutory Action	controller : issued alert flight crew : exited penetrated airspace flight crew : returned to assigned airspace
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Took off from boeing field, relied on GPS (gx-50) moving map for class G guidance. Too many lines on screen and I interpreted it to mean I was under class B segment with base at 3000 ft. At 2200 ft, boeing tower informed me I should be at 1700 ft. Flew east at 1700 ft until clear, then back up to 3000 ft under class B airspace. Should not have relied on moving map. Should have calculated class B transition points with GPS or VOR/DME.

Original NASA ASRS Text

Title: C210 PLT HAD INCURSION OF SEA CLASS B AIRSPACE.

Narrative: TOOK OFF FROM BOEING FIELD, RELIED ON GPS (GX-50) MOVING MAP FOR CLASS G GUIDANCE. TOO MANY LINES ON SCREEN AND I INTERPED IT TO MEAN I WAS UNDER CLASS B SEGMENT WITH BASE AT 3000 FT. AT 2200 FT, BOEING TWR INFORMED ME I SHOULD BE AT 1700 FT. FLEW E AT 1700 FT UNTIL CLR, THEN BACK UP TO 3000 FT UNDER CLASS B AIRSPACE. SHOULD NOT HAVE RELIED ON MOVING MAP. SHOULD HAVE CALCULATED CLASS B TRANSITION POINTS WITH GPS OR VOR/DME.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.