and where they are systematically missing. We collected existing spectroscopy in COSMOS to do this, as described in M15. These redshifts include (but are not limited to) those from VLT-VIMOS [@Lilly07; @LeFevre15], Keck-MOSFIRE [@Kriek15], Keck-DEIMOS [@Kartaltepe10], and Magellan-IMACS [@Trump07]. For the 2016A run we used only the spectroscopy taken in the COSMOS survey to identify undersampled regions of color space. The reason we could not incorporate spectroscopy from other fields for these observations is that the photometry between fields has to be highly consistent in multiple bands to reliably place galaxies on the same color map; at the time this problem had not been solved. Significant subsequent work has been done to solve this problem for upcoming runs, to be described in a forthcoming paper. The fields that have subsequently been put on a highly consistent color frame in *ugrizYJH* to the *Euclid* depth are VVDS, SXDS, and EGS (in addition to COSMOS).

Target Prioritization
---------------------

For the 2016A observations we used the SOM derived in M15 to prioritize regions of galaxy multicolor space that are currently undersampled by existing spectroscopic surveys. For observed fields in 2016A other than COSMOS (SXDS and EGS), we attempted to bring the photometry on 