Relative-gravity surveys were carried out using a ZLS Burris relative-gravity meter. The effect of solid Earth tides and ocean loading were removed from the data. Instrument drift was removed by evaluating gravity change during repeated measurements at one or more base stations. Absolute-gravity surveys were carried out using a Micro-g LaCoste, Inc. A-10 absolute-gravity meter. Vertical gradients between the different measuring heights of the absolute- and relative-gravity meters were measured using a relative-gravity meter and fully-adjustable tripod, and used to correlate the measurements between the two instruments. Relative-gravity differences and absolute-gravity data were combined using a least-squares network adjustment, as implemented in the software GSadjust (https://doi.org/10.5066/P9YEIOU8). Information about the network adjustment is provided under Data Quality in the metadata.