  The inner mass-profile of the relaxed cluster Abell 1703 is analysed by two
very different strong-lensing techniques applied to deep ACS and WFC3 imaging.
Our parametric method has the accuracy required to reproduce the many sets of
multiple images, based on the assumption that mass approximately traces light.
We test this assumption with a fully non-parametric, adaptive grid method, with
no knowledge of the galaxy distribution. Differences between the methods are
seen on fine scales due to member galaxies which must be included in models
designed to search for lensed images, but on the larger scale the general
distribution of dark matter is in good agreement, with very similar radial mass
profiles. We add undiluted weak-lensing measurements from deep multi-colour
Subaru imaging to obtain a fully model-independent mass profile out to the
virial radius and beyond. Consistency is found in the region of overlap between
the weak and strong lensing, and the full mass profile is well-described by an
NFW model of a concentration parameter, $c_{\rm vir}\simeq 7.15\pm0.5$ (and
$M_{vir}\simeq 1.22\pm0.15 \times 10^{15}M_{\odot}/h$). Abell 1703 lies above
the standard $c$--$M$ relation predicted for the standard $\Lambda$CDM model,
similar to other massive relaxed clusters with accurately determined
lensing-based profiles.
