Date: 201710
Local time of day: 1801-2400
Location: SFO.Airport, CA
Light: Night
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ramp SFO
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Confusion
Second reporter function: Captain; Pilot Flying
Anomaly: Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Became Reoriented
Contributing factors: Airport; Environment - Non Weather Related; Procedure
Primary problem: Ambiguous

Narrative: After exiting the Runway 1L at SFO; Ground Control cleared us to the ramp via E; B; H; and A. Because of the heavy traffic on A and an aircraft leaving the ramp; the Captain stopped the aircraft on A to let traffic out of the ramp. The Captain continued to monitor ground on VHF 1 while I announced that I was calling ramp on VHF 2. After the third clarification with Ramp; we were cleared via Spot 2; hold at Spot 4 for outbound traffic; and then to the gate.Due to extremely poor lighting; lack of signage; and confusion over charts; we entered the ramp towards Spot 1. However; once we realized that we were possibly on the wrong line; the Captain stopped the aircraft until we both agreed where we were and where we needed to go. The outbound aircraft was also heading towards Spot 3. We then crossed to Spot 2 and proceeded towards Spot 4. Once the aircraft passed on line one; I told Ramp we were at Spot 4; and the traffic was clear. Ramp acknowledged with no further comment and we taxied to the gate. At no time were we in conflict with any aircraft in the ramp area nor did Ramp advise us of any error.I had synced my EFB (Electronic Flight Bag) prior to the trip and thought that everything was updated correctly. However the first day of our trip; the SFO spot information page updated (two days prior) which changed the markings of Spots 1 and 2. This change did not make it into my spot information; so I was showing the reverse markings of Spots 1 and 2 on my EFB. After we taxied towards Spot 1 and could finally see the pavement markings; I verified my 10-9 page with the Captain and we were then in agreement with the correct location.The combination of poor lighting; construction and lack of signage makes it extremely difficult to discern the correct path into the ramp. It had been some time since either of us had been there at night and the taxi lighting had changed. The blue outlined median dividing the entryway between M1 and M2 appears to be the edge of the ramp coming from A and the only way into the ramp is via Spot 1. Additionally; there are no signs showing which line is which other than pavement markings and the lack of lighting leaves them completely blacked out until almost on top of them. There really needs to be some signage showing which line is which at the entrance of the ramp. In such a busy and congested area as SFO; this can greatly help a Crew taxiing in at night and with other factors such as low visibility and rain.


Second narrative: While taxiing into gate in SFO; ramp cleared us in from Taxiway Alpha via Spot 2 to Spot 4 and hold for aircraft coming out of the alley. We were then told we were cleared into our gate behind the outgoing aircraft. I had the 10-9 page up on my EFB; while the FO had the spot information diagram up on his page. The spot page had Taxiways M1 and M2 and the spot numbers backwards from my 10-9 page. There was another aircraft sitting just forward of Spot 1 waiting to be cleared to taxi to the runway. Being nighttime; with lots of construction and closures; I set the parking brake to wait for the aircraft at Spot 1 to taxi out.He taxied out and I maneuvered over Spot 1 to verify it actually said Spot 1. The FO assumed; correctly by his chart; that I was passing over Spot 2 as instructed. Confusion arose because my chart showed we needed to continue over to the next line where the actual Spots 2 and 4 were; which I did. This was obvious once we saw that the aircraft being towed out was on the actual Spot 3 and headed toward Spot 1. We continued to our gate behind the towed aircraft as previously instructed. We were never contacted by Ramp or Ground during this process; or after our initial taxi instructions.First and foremost the charts need to be accurate. Conflicting chart information led to the confusion. Also; better night signage and possible illumination for the spot numbers [would help].

Second callback: The reporter stated the biggest issue with taxiing in the area stated in the report is the signage is poor and the 10-9 page on the EFB had the spot numbers backwards. The reporter also stated the construction in the area may have contributed to the confusion.

Synopsis: B737 flight crew reported that a combination of poor lighting; construction; and lack of signage made it extremely difficult to discern the correct path into the ramp.