6 
Performance and Effect 
Since this instrument enables to measure the coordinates of the points on the 
aerial photographs with simplicity and with high precision, the calculation of the 
elements of the analytical aerial triangulation and those of the orientation result 
ed from the electronic computer may bring about more accurate results. 
Features of the Instrument 
This instrument is classified into two groups such as (A) mechanical photo 
comparator and (B) electronic coordinate recorder and tape perforating device. 
(A) Photocomparator 
( a ) Optical System for Observation 
(1) A single diapositive shall be observed with both eyes through an observ 
ing device consisting of two separate optical systems with interchange 
able magnifications of 20X and 4X. That is, at first, observation shall 
be conducted through both eyepieces and optical systems of low magnifi 
cation AX which displays a wide area (30 mm in diameter on the original 
plate) and the measured points shall be brought to the vicinity of the 
floating mark. Thereafter, the optical systems of magnification AX shall 
be replaced by those of magnification 20X keeping the eye-pieces un 
changed whcih are featured by small field of view (6 mm in diameter on 
the original plate). Binocular observation through these optical systems 
enables the measured point and. the floating mark to come to coincidence 
with precision. 
(2) Interchange of separate optical systems of high and low magnifications 
can be smoothly and arbitrarily carried out by changeover of the foot 
switch. 
(3) The floating mark is a light point of 0.03 mm in diameter which is made 
as an equal image distance system by using a semitransparent mirror 
and has a light quantity adjusting system. 
(4) The lamp of illumination of the diapositive has also a light quantity ad 
justing system. 
( b ) Loading of the Diapositive 
(1) The diapositive is held in the fixed position by the carrier. 
(2) A common plan parallel glass plate and the correction plate of the dis 
tortion of the photographic lens are also used as the carrier. 
( c ) Driving Mechanism of the Coordinate (X, Y) 
(1) X-boad, F-boad and an optical observation tower are fixed on a strong 
base supported by a tripod. 
(2) Displacement of the diapositive along X and Y can be conducted by 
means of precise driving screw (1mm in pitch) respectively. 
(3) The perpendicularity of X-axis to F-axis can be adjusted by adjusting 
the excentric axis of the guid pulley respectively. 
(4) In order to eliminate the the total pitch error in the fitting part of the 
driving screw and the female screw, super-high precision is maintained 
by attaching a pitch correction device. 
(5) The female screw into which the driving screw is fitted is made as an