Japan 2 
c. Photographic films and papers 
Before the War, aerial photographic film manufacturing was much impro- 
ved in our country, but now we are forced to use imported film i.e., XX Film 
of Eastman Kodak and Hyper Rapid Film of Gevaert Co. On the other hand, 
the photographic papers we use are mostly home made. Moreover, we have 
succeeded in manufacturing photographic papers with Aluminum foil inser- * « 
ted. 
d. Areas Photographed. 
The table below gives the statistics of areas (in km?) photographed, 
being classified with regard to their purposes. 
City Plan. Harbour Improv. River Improv. Forestry. Land Impror. High way plan. 
11,570 908 5,045 33,057 9,496 392 
Railroad plan. Transmission Sand guards Cadastral Others Total 
Line plan. 
249 5,132 1,308 1,575 3,609 72,341 
e. Technical Difficulties. 
It is sometimes very difficult to identify the signal marks placed on roads 
or sandy fields on aerial photographs and to distinguish the datails in sha- 
dowed area. This will bea defect in the application of aerial photogrammetry 
to forestry survey in moutaineous region etc. + x 
2. Plotting Instruments. Y * 
Immediately after the War, we had few plotting instruments. The aerial 
photo-surveyings were therefore operated mostly by applying the radial line 
method. Afterwards, higher accuracy was required especially for height mea- 
surements and efforts were made to devise the instruments such as a Triplex, 
a Multiplex and an Automatic Rectifier. 
These instruments were expedient for photogrammetric surveying during 
the period of occupation, but they have become of less utility value, since 
modern cameras and stereolotting instruments are imported. 
The photogrammetric instruments now in use in our country are: 
Two C-8 type and one C-5 type Stereoplanigraphs, one A-7 type Wild Auto- 
grayh five A-8 type Wild Stereoplotting instruments, three Kelsh Plotters, & ah 
about twenty Multiplexes, two SEG V type Automatic Rectifiers and two 
SEG I. 
On the other hand, less expensive 3rd order plotting instruments are 
urgently required for forestry survey and less accurate mapping. 
In response to these requirements, several instruments were devised, for 
instance, a large mirror stereoscope equipped with special floating marks for 
numbering trees, and a plotting stereoscope. with simple mechanism to e- 
liminate height distortion. 'The latter requires rectified photographs. 
3. Aerial Triangulation.