Why is it necessary for engineers to know the precise location of each GPS satellite in the system

1. crust 1 the metallic layer at the earth's center 2. inner core 3 the firm layer between the crust and the asthenosphere 3. lower mantle 2 the layer surrounding the inner core 4. asthenosphere 4 the semi-solid layer between the top layer and the upper mantle 5. upper mantle 5 the layer between the asthenosphere and lower mantle 6. top layer 6 the earth's outermost layer 7. outer core 7 the hottest part of the mantle

In which direction does the moving force of air flow? a-from warm temperatures to cold temperatures b-to areas of high pressure to areas of low pressure c-east to west d-from high elevations to low elevations

Which most likely was persia’s most valuable asset?