Widebody Transport
Ground Event / Encounter Other / Unknown
Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; General Maintenance Action
Human Factors; Airport
Inverted the parking spot coordinates in the initial position to initialize the IRUs. The sign at gates XX and XY have the wrong coordinates. Signs read N122.4 E1040.04. The correct coordinates are N 1 22.4 E 104 00.4. This needs to be fixed. The Jeppesen 10-9C1 pages that list parking spot coordinates is correct; the sign at the gate is wrong. The decimal place on the longitude is in the wrong place.  Our aircraft had been towed to the gate. When I initialized the FMS; the numbers were off so I used the coordinates off the gate sign to initialize. That position put the IRUs on the west coast of Africa. The GNS (Global Navigation System) RNP (Required Navigational Performance) began to climb after alignment and after some time; we received an unable RNP alert. Maintenance deferred the GNS and we proceeded without GNS and ADS-B.I realized what had happened on pushback from the gate and informed maintenance of the discrepancy in the gate sign. Wrong coordinates on the gate sign for gate XX and XY at WSSS. Fix the sign and always take the coordinates off the flight plan for FMS initial coordinates.
Air carrier First Officer reports entering IRU coordinates from the gate sign at WSSS which has a decimal point error. The east coordinate is entered as a 10.4 instead of 104 causing GPS error messages and a call for maintenance. The GPS is deferred and the actual cause of the anomaly is discovered during push back and corrected.