Elgg core doesn't have well-supported or documented location facilities.
If the current method works for you, you can use it, but I expect you'll need to support it yourself in the future when that function is removed from core.
From Cash Costello:
The geolocation code in Elgg is extremely inefficient. The plan was to replace it with a plugin with more efficient indexes, but it looks like it never got past the initial commit.
The deprecation message is harmless. It lets administrators know that the geolocation code will be removed from Elgg in the future (maybe Elgg 2.0?). Normal users do not see the message.
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