Time for homeowners to invest in green tarps.
Radar satellite imagery like the one coming from Sentinel can see surface water (like seen in all the orbit shots of the flooding areas), so could be used as an even better source of information to find even partially obscured or "misshaped" pools.
Plus, with the tarps you can't use the pool anymore. After all, it's not like you can see the satellites passing overhead
The orbit of nearly every satellite is tracked and known. Even US spy satellites are tracked[1]. Planes can do better, but unless you charter your own plane chances are you'll get photos from a weekday, which isn't exactly prime time for pool use. You can work around that by chartering your own plane, but that'll heavily eat into potential returns.
They report €10M from over 20,000 pools so you're talking an average of €500 — if you can afford to have a pool at all, are you really going to declare to your neighbors, friends, and family that you're willing to give up so much benefit from having it just to save that small a sum? Even if the tax officials don't have an anonymous tip line, that seems like a good way to cement your reputation as a bitter cheapskate.
Legend has it that rogue states/combatants would track US satellites using software and freely available data, and when they know one is going to fly overhead, they'd cover whatever they don't want photographed.
From rogue states to rogue swimmers...
"Papa, can I swim?", "In 13 minutes ma princesse, then we'll be safe."
Not sure how this works under French law. But in the U.S., doing something that so blatantly shows intent would jump penalties to felony tax fraud.
If someone gives you blue water, it's either gatorade or seriously not safe to drink.
> pure water has a slight blue color
I find it funny how reluctant most are to accept the color that particular substance. Ask a kid to draw a swimming pool, or the ocean, or earth. They'll usually draw it blue. No need to overthink this one.
Certainly the ocean near me is grey on grey days. I have no idea what swimming pools with a neutral grey bottom would look like from above on such days.
If you think the tax is wrong, work to get it changed.