Multi-frequency phase interference can be used to get sub-cm accuracy without needing ridiculous oscillators. The only problem is that you need to sample your

Multi-frequency phase interference can be used to get sub-cm accuracy without needing ridiculous oscillators. The only problem is that you need to sample your target several times with different frequencies to remove the ambiguity. Units like this: https://www.amazon.com/Bosch-GLM-35-Measure-120-Feet/dp/B00VI7WBWE https://www.amazon.com/Bosch-GLM-35-Measure-120-Feet/dp/B00V... that go for $75 (or less) do this. They're super accurate, the only downside is that it takes a second to cycle through all the necessary frequencies.