1. The problem statement, all variables and given/known data This is a lengthy problem with 3 parts, so I figured I would keep them separate. I have a diagram that corresponds with the problem as well. GPS receivers find their locations by measuring time differences between EM wave pulses emitted from satellites at known locations and known times in the sky. If the signals are emitted simultaneously from different satellite positions, then these time differences on the earth can give accurate position information when the satellite positions are known. However, a problem arises because simultaneous pulse emissions in the satellites' reference frame are not emitted simultaneously when viewed from the ground based GPS receiver. Consider the geometry for the satellites’ locations in the figure below with L=L’=12,000Km (γ=1 at this low satellite speed) and h=20,000 Km. The satellites are all moving at 4Km/s as shown. Suppose that at time t =t’=0 when satellite B is directly overhead of location D on the ground (x=x’=0), EM pulses are emitted simultaneously from satellite A and C in the satellites’ frame and their emission time and positions (in their reference frame) are sent to the GPS receiver on the ground. 1. First, calculate the time difference Δt between emission times from satellite A and satellite C as viewed from the GPS on the ground. 2. Relevant equations Δt=γΔt0 x=γ(x'=vt') t=γ(t'+vx'/c^2) 3. The attempt at a solution I know that there are two frames of reference here -- one for the satellites and one for the ground. As such, the Lorentz transformation equations will be needed. I'm having trouble figuring out exactly how to use them. Thank you very much for any help I receive!