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.
