Original: Measurements are from recent imagery , generally supplemented with Russian 1:200,000 scale topographic mapping as well as Jerzy Wala , Orographical Sketch Map : Karakoram : Sheets 1 & 2 , Swiss Foundation for Alpine Research , Zurich , 1990 .
Simplified: The confluence of the main Baltoro Glacier with the Godwin Austen Glacier is known as Concordia ; this location and K2 base camp are popular trekking destinations .