10 
weight, having a semi-matte surface for making notations or a glossy surface 
for copying and reproduction. In paper there is a choice of different degrees 
of scale stability; the most stable is obtained wherever making measurements 
is the dominant use. The anaglyphs are especially desirable where continuous 
and uniform coverage is needed in composite form of a long strip or broad area 
for group examination stereoscopically, and for three-dimensional presentation 
in reports and publications. Parallax and photographic coordinate measure- 
ments are made by use of contact prints on scale stable, double weight paper 
of semi-matte or other suitable writing and marking surface, for reconnais- 
sance surveys, for special purposes and determination of heights; and by use 
of contact prints on smooth, flat glass or on transparent, scale stable film 
for making precision tests and photogrammetric bridging of control. Precise 
measurements for bridging control mathematically and/or instrumentally, for 
topographie mapping, for planimetric and cadastral mapping, and for profiling 
and cross sectioning are made with reduction prints on glass, or contact 
prints on glass, printed emulsion to emulsion or printed with back of film neg- 
ative to emulsion on glass. Indexing is done with prints on paper which are 
contact printed from vertical photography negatives and transform printed from 
convergent photography negatives. 
In highway engineering in the United States, the significance and bene- 
fits of aerial photographs of all types for illustrative purposes are beyond 
monetary evaluation. This became especially so in recent years since, by law, 
it is mandatory in some circumstances that public hearings be held regarding the 
proposed relocation of highways and the location of new highway routes. For 
illustrations of conditions, characteristics, relationships, problems, proposed 
solutions, feasible route locations, and so forth, vertical photographs are and 
can be used as contact prints, photographic enlargements, photographic mosaics, 
anaglyphs, and stereograms. Opaque paper and transparent materials are used 
for making photographic contact prints, and also for enlargements printed by 
photographic or dry process. The transparent materials are often used as back- 
ground for plan sheets on which design data and rights-of-way are shown, 
instead of on topographic or planimetric maps. The photographic mosaics are 
assembled, copied, and printed on paper, at scales desired and according to 
need, as uncontrolled, semi-controlled, controlled, and precision types. The 
anaglyphs are made by photographic and/or other printing methods. Photographic 
stereograms are printed on glass for lantern slide purposes, and on photo- 
graphic or other type paper as illustrations in reports and publications. 
When oblique photographs are used for illustrative purposes, they are use- 
ful as perspective views of topography and/or land use; traffic movements, con- 
gestion, bottlenecks; obsolescence; before and after concepts; relationships; 
conditions; and feasible route locations, interchanges, bridge sites, and so 
forth. Obliques are used as contact prints on paper, as photographic enlarge- 
ments on paper, and as stereograms. Continuous-strip, stereoscopic, photo- 
graphs are especially useful as a record of conditions at one time for compar- 
ison with those of another; in making condition and inventory surveys, and 
traffic movement and density surveys; and in land appraisals and negotiations. 
The desirable scales for continuous-strip photographs are between 100 feet and 
20 feet to one inch (1:1,200 and 1:240). These especially large scale, stereo- 
scopic photographs are used as contact prints on paper, photographic enlarge- 
ments, anaglyphs, and stereograms. 
Aerial Surveys 
Aerial surveys enable members of the highway team to ascertain information 
and data in sufficient scope, adequate detail, and to essential accuracy, when 
and where needed. Aerial surveys make it easy for members of the highway team 
to work together or individually, as desirable, and help them to perform their 
WOrk, in proper sequence, while determining and comparing alternatives, dis- 
cussing problems and exchanging views, and achieving the best solution.