In an aside, John informs us that the angel measuring the walls of new Jerusalem measures according to human measurements (measure of man), which are also angelic measurements (Revelation 21:17). One of my students, Kameron Edenfield, suggests that this is another indication late in Revelation that angels and humans have been equalized, or even switched places. Human and angelic measurements are now equivalent.
In addition, the comment might indicate a contrast with the measurements of earlier sanctuaries. Paul tells us that the law came through angels (Galatians 3), and that includes the measurements of the tabernacle and its furniture. Moses ascended into a cloud of angels to receive the blueprints for the tabernacle. But the new Jerusalem is not built according to angels, but according to man. Specifically, it is measured according to measure of Jesus, the man, and then secondarily it is built according to the measure of those who are in Christ.