1. A method for determining a set of B1 field maps for different transmit channels of a radio-frequency transmit coil of a magnetic resonance apparatus, the method comprising: determining a first partial B1 field map having absolute B1 amplitudes for each of the different transmit channels, the determining of the first partial B1 field map comprising using a first acquisition technique, wherein an error value assigned to the absolute B1 amplitudes of the first partial B1 field map undershoots a predetermined limit value in a first subregion of a measurement parameter space; determining a relative partial B1 field map having relative B1 amplitudes for each of the different transmit channels, the determining of the relative partial B1 field map comprising using a gradient echo technique operating with a single gradient echo image; determining a spatial weighting function for mapping the relative B1 amplitudes onto the absolute B1 amplitudes taking into account the first partial B1 field maps and the relative partial B1 field maps of the different transmit channels; determining second partial B1 field maps from the relative partial B1 field maps, the determining comprising using the spatial weighting function, wherein an error value assigned to B1 amplitudes of the second partial B1 field map in a second subregion of the measurement parameter space lying at lower measurement parameter values than the first subregion undershoots the predetermined limit value, and wherein the first subregion and the second subregion immediately adjoin each other or overlap; determining the B1 field map for each of the different transmit channels from the first partial B1 field map and the second partial B1 field map for the respective transmit channel taking into account the first subregion and the second subregion, the error values, or the first subregion and the second subregion and the error values.