  The intrinsic anomalous Nernst effect in a magnetic material is governed by
the Berry curvature at the Fermi energy and can be realized in non-collinear
antiferromagnets with vanishing magnetization. Thin films of (001)-oriented
Mn$_{3}$NiN have their chiral antiferromagnetic structure located in the (111)
plane facilitating the anomalous Nernst effect unusually in two orthogonal
in-plane directions. The sign of each component of the anomalous Nernst effect
is determined by the local antiferromagnetic domain state. In this work, a
temperature gradient is induced in a 50 nm thick Mn$_{3}$NiN two micron-size
Hall cross by a focused scanning laser beam, and the spatial distribution of
the anomalous Nernst voltage is used to image and identify the octupole
macrodomain arrangement. Although the focused laser beam width may span many
individual domains, cooling from room temperature through the antiferromagnetic
transition temperature in an in-plane magnetic field prepares the domain state
producing a checkerboard pattern resulting from the convolution of
contributions from each domain. These images together with atomistic and
micromagnetic simulations suggest an average macrodomain of the order of $1
{\mu}m^{2}$.
