From what I understand, the relativistic effects are a lot less sensitive to nearby mass than the acceleration due to gravity (basically a 1/r relationship inst

From what I understand, the relativistic effects are a lot less sensitive to nearby mass than the acceleration due to gravity (basically a 1/r relationship instead of 1/r^2). So while a sensitive enough gravimeter can pick up a nearby fairly heavy mass moving and such an elevation change, an atomic clock is going to be much more sensitive to elevation changes than nearby changes in density.