Map showing the stations that participated in the EHT 2018 campaign (black circles), which differs from the EHT array in 2017 by the addition of the GLT. Co-located sites in Chile and Hawai‘i appear superimposed. The SPT projected location from the back of the map is indicated with a dashed circle, and baselines to this station are represented with dashed-lines. While the SPT cannot observe M 87^*, it observed 3C 279 and was used to calibrate the data.