The rectified picture of the terrain is not a map and must first be inter-
preted by the user. However, precise measurements can be taken from the
orthophotogram. In addition, the orthophotogram contains a wealth of informa-
tion and a large amount of detail that is not present in the most complete map.
Even if one argues that itis one of the functions of a map to select information,
there is no doubt that there are several applications in which a perfectly rectified
photograph, possibly completed by contour lines, may prove to be most useful.
Therefore we would like to suggest that an orthophotogram is a special mapping
product that is typicalof photogrammetric technique and that may become a most
valuable addition to conventional maps. As a product it is similar to the well-
known photoplans. With the creation of the Orthophotoscope a new, superior
technique has been introduced to meet many technical and economic requirements
in the mapping field.
The automatic stereoplotting device invented in Canada is an extraordinary
achievement of modern technology that will drastically change the future mapping
technique and its structural characteristics. We are referring here to a device
called Auscor or Stereomat, developed by the Hunting Survey Corporation Limited
of Toronto. This device, designed at present for the Nistri Photomapper, per-
forms the relative orientation of a stereogram, reads elevations, draws profiles
in the stereomodel, and draws contour lines automatically. The extremely im-
portant feature of the device is its surprisingly high accuracy in some of the +
above-mentioned operations and its speed, which is several times faster thanthat
of a human operator. If one considers that the accuracy of future automatic
stereo operations will be further improved and, especially, that the speed of
some of these operations may become 10 to 50 times more rapid than the speed
of the human operator (at present, automatic contouring is up to 10 times faster
than the contouring performed by a human operator), it will not be difficult to
visualize the changes taking place in the modern mapping technique. With the
achievement of the complete automation of some stereoplotting operations a
decisive step has been taken toward a further, most unexpected development in
photogrammetric technique and instrumentation.
Scale of Photographs and the Mapping Scale
As already mentioned, there is a general trend to decrease the scale of
photography for a given mapping scale. The fact that this is not always evident
in the countries listed in Table II may be explained by a lack of adequate flying
equipment rather than by the accuracy requirements. It should also be noted
that about 50% of member countries have not sent in their answers to the
questionnaire, and among them are countries that use photo scales of up to
1:70,000 in their official projects for 1:50, 000 maps.
Some basic information on small-scale mapping supplied by the national
reporters to Commission IV, is summarized in Table II.
