  We present beam measurements of the CHIME telescope using a radio calibration
source deployed on a drone payload. During test flights, the pulsing
calibration source and the telescope were synchronized to GPS time, enabling
in-situ background subtraction for the full $N^{2}$ visibility matrix for one
CHIME cylindrical reflector. We use the autocorrelation products to estimate
the primary beam width and centroid location, and compare these quantities to
solar transit measurements and holographic measurements where they overlap on
the sky. We find that the drone, solar, and holography data have similar beam
parameter evolution across frequency and both spatial coordinates. This paper
presents the first drone-based beam measurement of a large cylindrical radio
interferometer. Furthermore, the unique analysis and instrumentation described
in this paper lays the foundation for near-field measurements of experiments
like CHIME.
