As the discussion progresses from the likelihood that there is water on Mars through yes, near the poles, now to to Is there really a frozen lake near the equator on Mars? and There's a lot of subsurface water ice at many mid-latitude sites..., I'm wondering how a water resources map will be generated in the next few decades to identify the best candidate locations for water-intensive efforts such as making methalox and growing food.
Would the workhorse likely be a few satellites with neutron detectors, or multi-spectral radar, or sensitive hyperspectral vis-IR imagery, or is there not much room for improvement on space-based observation and the search would have to be done by surface or lower atmospheric craft (e.g. rovers and aircraft)?
Some of the earlier data is mentioned in answers to the question What's the scientific evidence of water for return trip methalox on Mars?
update: There are some problems with some observations: Help understanding the false MRO observations of hydrated minerals on Mars