  Navigation guided by natural language instructions is particularly suitable
for Domestic Service Robots that interacts naturally with users. This task
involves the prediction of a sequence of actions that leads to a specified
destination given a natural language navigation instruction. The task thus
requires the understanding of instructions, such as ``Walk out of the bathroom
and wait on the stairs that are on the right''. The Visual and Language
Navigation remains challenging, notably because it requires the exploration of
the environment and at the accurate following of a path specified by the
instructions to model the relationship between language and vision. To address
this, we propose the CrossMap Transformer network, which encodes the linguistic
and visual features to sequentially generate a path. The CrossMap transformer
is tied to a Transformer-based speaker that generates navigation instructions.
The two networks share common latent features, for mutual enhancement through a
double back translation model: Generated paths are translated into instructions
while generated instructions are translated into path The experimental results
show the benefits of our approach in terms of instruction understanding and
instruction generation.
