Widebody; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 35; Flight Crew Total 11500; Flight Crew Type 5000
Confusion; Situational Awareness
Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Incursion Taxiway
Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Procedure; Weather; Chart Or Publication
Taxiing out of North Cargo we were given Lima to Bravo.  There was snow on the ground obscuring the taxi lines and the Airport info page 10-9 depicts Lima as a large paved area connected to Bravo; but when we taxied we saw some markers that we went around to the left and then onto Bravo.  When we pulled up the Parking gates 10-9B page diagram we saw that there is an area between Lima and the General Aviation ramp that is not depicted on the 10-9 airport info page.  I believe we stayed on the taxiway at all times but we weren't on Lima.  The 10-9 page needs to be updated to show that area.
Upon reaching the area where Taxiway L left the cargo ramp area we mistakenly taxied via the general aviation ramp to enter Taxiway B. There was no incident and we continued taxi and took off uneventfully. In reviewing the 10-9 page; the taxi diagram is misleading in showing taxiway L on a large paved ramp area. It shows a different layout than the 10-9B page. In reality there are some ground markers separating L from the large general aviation ramp area (as depicted on 10-9B). The 10-9 page should be fixed by Jeppesen to more accurately reflect the true layout.
A crew departed the BOS North Cargo Ramp with clearance to Taxiway B via Taxiway L but turned left after leaving the Cargo Ramp and taxied via the General Aviation Ramp to Taxiway B. The event occurred during night conditions with snow. More accurate North Cargo airport charting was suggested.