BE33 pilot deviates from track due to GPS unit error in ZOB airspace.

Attributes
ACN	414770
Time
Date	199809
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ihd
State Reference	PA
Altitude	msl bound lower : 8000 msl bound upper : 8000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob tower : rno
Operator	general aviation : personal
Make Model Name	Bonanza 33
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : commercial pilot : instrument pilot : cfi pilot : atp
Experience	flight time last 90 days : 75 flight time total : 3500 flight time type : 250
ASRS Report	414770
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe other spatial deviation
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Using GPS to navigation airway V474-ihd-V35, I was told that I was 20 degrees off course. Accuracy of GPS in doubt after checking with VOR receiver. Backed up GPS with VOR receiver throughout remainder of trip. GPS will be sent to radio repair to test accuracy.

Original NASA ASRS Text

Title: BE33 PLT DEVIATES FROM TRACK DUE TO GPS UNIT ERROR IN ZOB AIRSPACE.

Narrative: USING GPS TO NAV AIRWAY V474-IHD-V35, I WAS TOLD THAT I WAS 20 DEGS OFF COURSE. ACCURACY OF GPS IN DOUBT AFTER CHKING WITH VOR RECEIVER. BACKED UP GPS WITH VOR RECEIVER THROUGHOUT REMAINDER OF TRIP. GPS WILL BE SENT TO RADIO REPAIR TO TEST ACCURACY.

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.