Refer to figure.
Lambert chart: Convergency = Change of longitude º x Convergence factor

Where convergence factor equals sin of Parallel of Origin.

Parallel of Origin: half way between standard parallels - in this case, standard parallels 50ºS and 56ºS => Parallel of origin is 53ºS

Convergence factor = Sin 53º = 0.7986

• Both points are on latitude 53ºS. Therefore, RLT = 090ºT
• Difference between RLT and GCT = Conversion Angle

First Step: Calculate GCT at B (from RLT at B and Conversion Angle)

At B
Conversion angle = 1/2 change of longitude x convergence factor

= 1/2 (35º) x 0.7986 = 13.98° (approx. 14°)

GCT at B = RLT - Conversion angle = 090° - 014° = 076°

Second Step: using convergency, use GCT at B to calculate GCT at 175°W

Convergency = change of longitude x convergence factor

= 5° x 0.7986 = 4°

• GCT at 175ºW > GCT at B
• At 175ºW = GCT at B + Convergency

GCT = 076° + 004° = 080°