Narrative:

After a CAT3 landing at seattle in dense fog; we eventually cleared all runways at papa and were cleared to taxi northbound on bravo to spot 55. We made our way northbound on bravo and cross-checked our position with extra care referencing commercial chart 20-9F. Based on this chart; we determined that we would pass 'red circle #6' and make the first right turn over to spot 55. (Restricted visibility limited our ability to cross-check some other cues such as other taxiway signage.) to our surprise; we found ourselves at spot 66. We contacted ramp and reported our actual position and were cleared into the ramp area and gate without incident. (There was no outbound traffic.) after further review of the chart and looking at the area later in good visibility; it appears that red ball #6 (geographic position indicator #6) is incorrectly depicted on charts 20-9D; east; F; 'G.' it is actually located just south of the taxi line to spot/box #66 (on taxiway bravo). Review depiction of ground position indicator #6 on above mentioned charts and correct it.callback conversation with reporter revealed the following information: the reporter has returned to sea several times and verified after looking very closely at these taxiway markings that indeed taxiway spot 6 is very close to abeam spot 66. This fact makes the chart misleading but during VMC most pilots do not notice how far the marking is from the indicated spot. During IMC and taking the marking literally; a taxi error will most likely occur.

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Original NASA ASRS Text

Title: AN AIR CARRIER PILOT TAXIING IN LOW VISIBILITY ON TAXIWAY 'B' TO RAMP POSITION 55; EXITED TAXIWAY 'B' AT TAXIWAY SPOT 6 AND DISCOVERED THE AIRCRAFT AT RAMP SPOT 66. THE COMMERCIAL AIRPORT CHART APPEARS TO DEPICT TAXIWAY SPOT 6 INCORRECTLY.

Narrative: AFTER A CAT3 LANDING AT SEATTLE IN DENSE FOG; WE EVENTUALLY CLEARED ALL RUNWAYS AT PAPA AND WERE CLEARED TO TAXI NORTHBOUND ON BRAVO TO SPOT 55. WE MADE OUR WAY NORTHBOUND ON BRAVO AND CROSS-CHECKED OUR POSITION WITH EXTRA CARE REFERENCING COMMERCIAL CHART 20-9F. BASED ON THIS CHART; WE DETERMINED THAT WE WOULD PASS 'RED CIRCLE #6' AND MAKE THE FIRST RIGHT TURN OVER TO SPOT 55. (RESTRICTED VISIBILITY LIMITED OUR ABILITY TO CROSS-CHECK SOME OTHER CUES SUCH AS OTHER TAXIWAY SIGNAGE.) TO OUR SURPRISE; WE FOUND OURSELVES AT SPOT 66. WE CONTACTED RAMP AND REPORTED OUR ACTUAL POSITION AND WERE CLEARED INTO THE RAMP AREA AND GATE WITHOUT INCIDENT. (THERE WAS NO OUTBOUND TRAFFIC.) AFTER FURTHER REVIEW OF THE CHART AND LOOKING AT THE AREA LATER IN GOOD VISIBILITY; IT APPEARS THAT RED BALL #6 (GEOGRAPHIC POSITION INDICATOR #6) IS INCORRECTLY DEPICTED ON CHARTS 20-9D; E; F; 'G.' IT IS ACTUALLY LOCATED JUST SOUTH OF THE TAXI LINE TO SPOT/BOX #66 (ON TAXIWAY BRAVO). REVIEW DEPICTION OF GROUND POSITION INDICATOR #6 ON ABOVE MENTIONED CHARTS AND CORRECT IT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE REPORTER HAS RETURNED TO SEA SEVERAL TIMES AND VERIFIED AFTER LOOKING VERY CLOSELY AT THESE TAXIWAY MARKINGS THAT INDEED TAXIWAY SPOT 6 IS VERY CLOSE TO ABEAM SPOT 66. THIS FACT MAKES THE CHART MISLEADING BUT DURING VMC MOST PILOTS DO NOT NOTICE HOW FAR THE MARKING IS FROM THE INDICATED SPOT. DURING IMC AND TAKING THE MARKING LITERALLY; A TAXI ERROR WILL MOST LIKELY OCCUR.

Data retrieved from NASA's ASRS site as of April 2012 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.