C172 pilot has an altitude deviation during ILS approach opf.

Attributes
ACN	721031
Time
Date	200612
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : opf.airport
State Reference	FL
Altitude	msl single value : 500
Environment
Flight Conditions	IMC
Weather Elements	Rain Fog
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mia.tracon
Operator	general aviation : personal
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Navigation In Use	ils localizer & glide slope : 9r
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private pilot : instrument
Experience	flight time last 90 days : 7 flight time total : 620 flight time type : 400
ASRS Report	721031
Person 2
Affiliation	government : faa
Function	controller : approach
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued advisory flight crew : returned to original clearance
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

Cleared for runway 9R approach at opf. Controller correctly gave me instructions 'maintain 1700 ft until established.' once on the localizer I did not check my position relative to the OM (moltz) and acted as if I was inside of moltz (ie; between moltz and the airport). I initiated descent and followed a false GS signal down until advised to 'check altitude' and told that I was still outside of moltz. At this point I climbed until reestablished on the approach and proceeded to land normally.

Original NASA ASRS Text

Title: C172 PLT HAS AN ALTDEV DURING ILS APCH OPF.

Narrative: CLRED FOR RWY 9R APCH AT OPF. CTLR CORRECTLY GAVE ME INSTRUCTIONS 'MAINTAIN 1700 FT UNTIL ESTABLISHED.' ONCE ON THE LOC I DID NOT CHK MY POS RELATIVE TO THE OM (MOLTZ) AND ACTED AS IF I WAS INSIDE OF MOLTZ (IE; BTWN MOLTZ AND THE ARPT). I INITIATED DSCNT AND FOLLOWED A FALSE GS SIGNAL DOWN UNTIL ADVISED TO 'CHK ALT' AND TOLD THAT I WAS STILL OUTSIDE OF MOLTZ. AT THIS POINT I CLBED UNTIL REESTABLISHED ON THE APCH AND PROCEEDED TO LAND NORMALLY.

Data retrieved from NASA's ASRS site as of January 2009 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.