We measured the RTT from each landmark to all the other landmarks within a known distance. We noted the landmarks lat/long, its name and address, the number of samples, the calculated correlation coefficient R^2 between RTT and distance, the minimum, 25 percentile, median, 75 percentiles and maximum for the RTT, distance, and alpha. Using Excel we plotted the number of samples (n) and the R^2 versus the country/region. Two examples are shown below for different maximum known distance thresholds.