The application of aerial photographs for Japanese forestry purpose have been increasing year by year. Also many researches are carried out at several universi ties, Forest Experiment Station, covernment organizatirns or at the Forest Technial Association, mainly.
The results of those researches are published as the reports of these institutes or societies, also some are presented at the meeting of the Japan Forestry Society.
Regarding to the photo-forestry, 6 reports have published and 12 was presented at the meeting since 1961, Jan. to 1962, may. Beside them, 9 reports had printed on the Journal of “the Air-photo in Forestry” (Shinrin Kosoku) during this period.
As the tendency of the researches, the stand volume estimation methods with the combination of sampling works are studied at the institutes of universities and the survey purposes are at government organizations and at the Association.
The Governmeut Forest Experiment Station has been carried out the foundamental researches of photo applications and analysis including every forestry purpose.

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The author adopts the line connecting the positions of the optical center of the camera when two photographs were taken as X axis and κ₁and ψ₁ as the orientation elements for the first photograph and κ₂, ψ₂ and ω₂ as those for the second one.
[3] The author discusses several treatments for solving the parallax equation with a numerical example of a simple model. He points out that when the equation is treated by expanding in Maclaurin's series as y₂-y₁=-x₁κ₁-x₁y₁/fφ₁+x₂κ₂+x₂y₂/fφ₂+f (1+y₂²/f²) ω₂, where x_i and y_i are observed photographic co-ordinates, in order to sum up the successively obtained approximate values with the preceding ones in the course of iteration, it is necessary to take into consideration of a correction δκ_i=-ω_i0Δφ_i+Δκ_i/2 (φ_i0²-ω_i0²+2φ_iΔφ_i0), δφ_i=ω_i0Δκ₁-1/2 {ω_i0²Δφ_i+φ_i0 (Δκ_i) ²} and δω_i=-φ_i0Δκ_i+ω_i0/2 { (Δφ_i) ²- (Δκ_i) ²+2φ_i0Δφ_i) } resulting from the second order terms in 2 the rotation matrix, if the orientation elements are not so small. After all the author presents the observation equation by expanding the rigourous equation U=y ₍₁₎ -y ₍₂₎ =0 in Taylor's series around a set of approximate values as follows.
U₀+ (∂U/∂κ₁) ₀Δκ₁+ (∂U/∂φ₁) ₀Δφ₁+ (∂U/∂κ₂) ₀Δκ₂+ (∂U/∂φ₂) ₀Δφ₂+ (∂U/∂ω₂) ₀Δω₂=0,
where ∂U/∂κ₁=-x ⁽¹⁾ cos φ₂-f (1+y ^{(1) 2}/f²) sin φ₁, ∂U/∂φ₁=-x ⁽¹⁾ y ⁽¹⁾ /f, ∂U/∂κ₂=x ⁽²⁾ cos φ₂ (cos ω₂-y ⁽²⁾ /f sin ω₂) +f (1+y ^{(2) 2}/f²) sin φ₂, ∂U/∂φ₂=x ⁽²⁾ (sin ω₂+y ⁽²⁾ /fcos ω₂), ∂U/∂ω₂=f (1+y ^{(2) 2}/f²) and x _(i) and y _(i) are rectified co-ordinates of points on the photographs-defined by eqs. (19) . In the last treatment, the results can be algebrically summed up without the consideration of the correction described above, even when the orientation elements are not so small.

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Stereo-photogrammetry is a means by which we make measurements on a model constructed by stereo-viewing. The model may often be exposed to deformation. This model deformation is caused by some displacements of image points on photographs. The displacements are only on two-dimentional plane, however, the deformations are of three dimentional.
The relationship between them is not yet clear. In spite of some theoretical investigations so far published, experiments thereby are scarecely in our sight.
In the case of conventional mechanical method, the experiment is not so easy. But by analytical method we can give a image point any displacement intentionally and test the deformation comparing with the standard model.
Some results of the preliminary experiment for model deformation by analytical method will be shown below.

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In Aerial Triangulation, the method of least squares is applied to adjust the curve of error. However this method requires much computations for complicated curves. Involving dependent and independent variables with random errors, it is believed that this theory is not logical for practical use.
This article is a study for a reasonable arithmetic process which can be used in theory and practice.
The results of our experiment shows that this new process required less computation as the use of statistics was introduced.

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As the simple examination of photographs taken for the Large scale mapping some visual tests and simple criterions are adopted: that is, overlapping Oⁱi-1, on Fig. 1, Connection angle αⁱ R on Fig. 2, Rotation angle on βⁱ on Fig. 3, and Deviation yⁱ from the mean flight line and take statistical mean of these values and absolute values, which are defived as P₁, P₂by formula (1), P₃, P₄ by formula (2), P₅, P₆ by formula (3) and P₇, P₈by (4) . The Results are shown on Table I and II, and Conclusions are as follows; the standard overlap can be taken about 56%, the single eingised aeroplane is not favorable in our case, the number of photographs in one strip is desired to be less than 30.

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