Positions of the BlazEr1 sources in Galactic coordinates. The different colors and symbols indicate the blazar types in the catalog. Candidates, especially BCUCs, dominate the sample. The overdensity along l ∼ 240° coincides with the footprint of BROS. Confirmed blazars are displayed by filled symbols, candidates are shown in the same color without filling. All the following figures will adapt the same color and symbol scheme.