PROBLEMS RELATING TO RETICULATION 
In photogrammetry, the damaging effects in the plotting process 
due to the deformations which the photographic images undergo 
in the development bath, drying and other effects, are well known. 
This is especially true if the support of the negative image is com 
posed, as usually, of film, extending these deformations also on the 
diaspositives, because of the temperature and humidity of the nega 
tive film when the diapositive is made. 
Photogrammetry cameras are generally provided with four 
marginal reperes (in the corners) to which can be associated 
another four marginal reperes in nature, situated in the centre of 
the sides of the square. These reperes projected on the film at the 
moment of the taking, can furnish elements of control over the 
general deformations of the image; for example lengthening or 
contracting in the longitudinal or transversal sense, or also rhom 
boidal deformations. But unfortunately they cannot furnish any 
element of control over distortions appearing in the photographic 
field. 
To avoid this inconvenience in some types of cameras there has 
been placed a glass slide parallel between the lens and the film, so 
that the external surface of this slide corresponds to the plane of for 
mation of the picture. On this surface there are inscribed numerous 
reference markings, blackened little crosses, placed according to a 
reticule of well known dimension. Against this very side, at the 
moment of the taking, the film is laid out. The use of this glass slide