There are some algorithms that are trivial to implement with Geohashes that are non-trivial with lat-long coordinates. For example, given a set of n points find the k nearest neighbors. To do this with geohash you maintain an ordered list of geohashes, and find k points adjacent in the list. Doing this efficiently with lat-long requires some relatively exotic data structures like an R-tree or k-d-tree.
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There are some algorithms that are trivial to implement with Geohashes that are non-trivial with lat-long coordinates. For example, given a set of n points find the k nearest neighbors. To do this with geohash you maintain an ordered list of geohashes, and find k points adjacent in the list. Doing this efficiently with lat-long requires some relatively exotic data structures like an R-tree or k-d-tree.
That is a lossy, incorrect algorithm. Sorry, there is not a continuous mapping from one dimension that covers two dimensions.