  Sensors are routinely mounted on robots to acquire various forms of
measurements in spatio-temporal fields. Locating features within these fields
and reconstruction (mapping) of the dense fields can be challenging in
resource-constrained situations, such as when trying to locate the source of a
gas leak from a small number of measurements. In such cases, a model of the
underlying complex dynamics can be exploited to discover informative paths
within the field. We use a fluid simulator as a model, to guide inference for
the location of a gas leak. We perform localization via minimization of the
discrepancy between observed measurements and gas concentrations predicted by
the simulator. Our method is able to account for dynamically varying parameters
of wind flow (e.g., direction and strength), and its effects on the observed
distribution of gas. We develop algorithms for off-line inference as well as
for on-line path discovery via active sensing. We demonstrate the efficiency,
accuracy and versatility of our algorithm using experiments with a physical
robot conducted in outdoor environments. We deploy an unmanned air vehicle
(UAV) mounted with a CO2 sensor to automatically seek out a gas cylinder
emitting CO2 via a nozzle. We evaluate the accuracy of our algorithm by
measuring the error in the inferred location of the nozzle, based on which we
show that our proposed approach is competitive with respect to state of the art
baselines.
