What is the significance of 'к востоку от 180°' and 'к западу от Гринвича'?

'к востоку от 180°' means 'east of 180°' and 'к западу от Гринвича' means 'west of Greenwich'. These are references to longitude, with 180° being the International Date Line, and Greenwich being the Prime Meridian (0° longitude).