It's true. But survey-grade coordinates generally are used in a universal transverse Mercator, or in some locales a Lambert conic or some other locally useful p

It's true. But survey-grade coordinates generally are used in a universal transverse Mercator, or in some locales a Lambert conic or some other locally useful projection. Those projections take into account such things as the deviation of the earth's shape from a perfect sphere. Rule about lat/long precision: If somebody says the words "datum" or "projection" to you, and you say "huh?", then you only need four digits after the decimal point in your lat/long coordinates. On the other hand, if you're designing an outdoor parking lot and you don't want puddles, please use survey-grade coordinates.