In irregular astigmatism the orientation of the principal meridian
changes from point to point across the pupil.
In 1815, two surveyors set out with stakes, chains, and compasses to establish Michigan Territory's baseline and principal meridian
, the standard coordinates by which townships and property descriptions would later be established.
After 'zeroing' the focimeter, the first step is to establish the power of the principal meridian
with the higher absolute back vertex power (BVP).
Peter Dorsher's study of Myers' nine myofascial meridians revealed that, 'In 8 of 9 comparisons, there was substantial overlap in the distributions of the anatomically derived myofascial meridians with those of the acupuncture Principal Meridian
is selected and attributed to the principal meridian
the axis varied +- 15-30o from 180 principal meridian
, which is in agreement with other studies conducted on the refractive errors of children.
A piece of land is described as "the NW 1/4 of the SE 1/4 section 14, T 6 N, R 11 W, 6th Prin Mer." The translation is "the northwest quarter of the southeast quarter of section 14 in township 6 north and range 11 west of the 6th Principal Meridian
In previous work  each principal meridian
on the front surface of a cornea was independently aligned with the focused mires of a keratometer.
* The K-readings can be used to determine the radius of the steeper meridian, along with the use of axial edge tables to finalise the peripheral curves for each principal meridian
, or it may be possible to determine the fit from the fluorescein pattern
He is a charter member of the 6th Principal Meridian
Surveyors, vice president for Southern Colorado Professional Land Surveyors, a member of the Colorado Department of Transportation Survey Activities Committee (a group overseeing surveying within the department), project manager for the Statewide GPS Network, surveying instructor for the department, chair for Colorado Section - American Congress on Surveying and Mapping, and a member of the Civil Technology Advisory Committee for Trinidad State Junior College and the University of Southern Colorado.