We address this question by attempting to cross-calibrate and merge space-based magnetogram data with ground-based data to create a "hybrid synoptic map" for input into the WSA/Enlil model. The space- and ground-based magnetogram data are from SDO/HMI and GONG, respectively. Both full-disk magnetograms and merged synoptic maps are analyzed. WSA/Enlil runs for Carrington Rotation 2182 (October 2016) are performed with HMI, GONG, and merged synoptic maps and the predictions compared with ACE in-situ solar wind data. Our results show that instrumental and spatial resolution differences prevent merging L5 and ground-based SEL data to create an accurate synoptic field map unless the spatial resolution is severely degraded. In addition, we show that both space- and ground-based magnetograms taken from the ecliptic plane significantly underestimate the polar flux, in the case of CR2182 causing a blown forecast of the G3 geomagnetic storm on 25 October 2016. We conclude that the only way to provide accurate full-Sun magnetic field data to solar wind models is to measure the entire Sun with multiple, identical, space-based instruments, including polar orbiting missions to ensure that polar flux levels are captured.