REPORT FOR 1897--PART II. APPENDIX NO. 10.

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of the iconometric constructions will arise, inasmuch as such pictured stations (s and s1) will be “kernelpoints.”

The line of intersection (JO) of the two pictnre planes (MN and M' N‘) may also play an important part in the iconometric platting, not only for pictures exposed in vertical planes, but even more so when they are exposed in inclined planes.

. If two pictures MN and M' N' are given (in fig. 16 their traces are represented as HH and H' H', respectively) representing the same object (viewed from two stations S and S'), then the pictures s and s' (“ kernelpoints”) of the reciprocal caméra stations may be located upon the picture planes by construction (if they are not shown in the field of the pictures), as shown in

fig. 16.

The horizontal projections (s, and si) of the “ kernelpoints” (s and s') are identical with the points of intersection of the base line (SS') and the pictures traces (HHand H1 H1). The horizontal projections of the line of intersection (JO, fig. 15) of the two picture planes (MN and M1 N') will be represented by the point of intersection (i) of the two picture traces (HH and H' H').

Hence, if we revolve the picture planes about their ground lines until they fall within the horizontal plane of the ground plan, the line JO, fig. 15 (common to both picture planes), will be represented by the lines

i(J), fig. 16, and the “kernel- h h'

points” s and s' of the re-volved planes will fall upon the lines Si(s) and s'i(s'), respectively. (These lines are perpendiculars upon the picture traces (IIH and H'H’) in the horizontal projections of the “kernelpoints”.)

To find the lengths Si(s) and s\(s') (ordinates of the “kernelpoints” in the picture planes), perpendiculars are erected in S and 8f, fig.

16, and their lengths are made equal to the élévations of the respective caméra horizons above the ground plane = $($) and S1 (S'), respectively. The line (8)(8f), connecting the caméra stations 8 and (in fig. 16 the vertical plane passing through

the caméra stations 8 and 8' h as been revolved about the horizontal projection of the base line SS' until it coïncides with the horizontal ground plane) will intersect the lines s fs) and s'^s') (which are perpendicular to the horizontal projection of the base line in the “ kernelpoints” sx and s'i), and the lengths sx(s) and s'i(s') will equal the ordinates of the kernelpoints. In this manner the “kernelpoints” may be located in the picture plane of any photograph.

(2) Use ofihe Une of intersection ( JO) oftwo picture planes (MN and M'N‘) which show identical ohjects viewed from two different stations (s and sr).—If a sériés of characteristie points of the terrene, pictured in a vertical picture plane MN, fig. 17, are connected with the “kernelpoint” s by straiglit lines, these will (when prolonged) intersect the line JO, and if the pictures of the identical points in the vertical picture plane M'N' are joined with the “kernelpoint” s', and if these lines are likewise prolonged to intersect the line (JO), forming the intersection of the two picture planes (MH and M'N1), the sériés of intersections of JO with the first group, belonging to MN, will be identical with the intersections of JO with the second group of lines, belonging to M'N'.

If we now imagine the line JO provided with a scale of equal parts, with zéro in the ground plane 6r6r, fig. 17, lines drawn through the “kernelpoints” and identical points of objects pictured

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