Optical Square

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optical square

[′äp·tə·kəl ′skwer]
A surveyor's hand instrument used for laying of right angles; employs two mirrors at a 45° angle.

Optical Square


a very simple geodetic instrument that is used to lay off angles that are multiples of 90° or of 45°.

In a prism square (see Figure 1), the direction of a ray originating from the flag on the right is changed by 90° after refraction and internal reflection. To lay off the angle by which the direction of the ray is changed, a second flag is set up in such a way that, when it is seen over the instrument, it is exactly above the image of the first flag in the instrument.

Figure 1. A prism square

Optical squares are used to solve geometric problems on a terrain and to carry out plane surveys.

References in periodicals archive ?
--Testing and, if necessary, adjusting of all instruments (theodolite, levelling instrument) and equipment (measuring tape, levelling staffs, optical square) to be used during the course of the camp.
And a simple setup of our P-405 Optical Square will easily measure cross-slide squareness.
Tenders are invited for Supply of Pycnometer, La Chatelier Water Bath, Density Basket, Vibrating Machine, Digital Balance, Laboratory CBR Test Apparatus(Motorised), Compression Testing M/C, Universal Automatic Compactor, Blaine s air permeability test apparatus, Prismatic Compass, Plane Table , Conventional Surveying equipments like Chain, Tape, Optical Square, Levelling Staff, Ranging Rods etc.
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