Modern Estonian orthography is based on the Newer Orthography created by Eduard Ahrens in the second half of the 19th century based on Finnish orthography. The Older Orthography it replaced was created in the 17th century by Bengt Gottfried Forselius and Johann Hornung based on standard German orthography. Earlier writing in Estonian had by and large used an ad hoc orthography based on Latin and Middle Low German orthography. Some influences of the standard German orthography — for example, writing 'W'/'w' instead of 'V'/'v' persisted well into the 1930s.

Answer this question, if possible (if impossible, reply "unanswerable"):  In what Orthagraphy does Modern Estonian orthography have its basis?
Newer Orthography