Report onGroup Meeting on Aerial Photographyand Photogrammetry Applications

to Highway Work

GORDON GRACIE,*

Instructor in C1'vil Engineering,Univ. of Illinois

T HIS group meeting was held on February26, 1959, in the Illini Union Ballroom,

University of Illinois. H. M. Karara, Assist­ant Professor of Civil Engineering at theUniversity of Illinois, was chairman, and thefollowing were the discussion leaders:

A. BrandenbergerAssoc. Prof. of PhotogrammetryOhio State Univ.Columbus, Ohio

H. L. BrantleyChief, Aerial Surveys BranchIllinois Div. of HighwaysSpringfield, III.

E. M. RaleyAsst. Chief EngineerPhotronix Inc.Columbus, Ohio

N. ChryssafopoulosAsst. Prof. of Civil EngineeringUniv. of IllinoisUrbana, Ill.

The following is a summary of the principalitems which were discussed during the meet­ing.

Discussion of the first question, "What isPhotogrammetry, and what are its basic prin­ciples?", was led by Prof. Brandenberger. Theprincipal items discussed were as follows:

1. Aerial photogrammetry predominatesover terrestrial photogrammetry in high­way work.

2. Although rectified single-image photo­graphs may sometimes be used, the bulkof the work is done using double-imagephotographs in special stereoscopic plot­ting instruments (automatic plotters).

3. Ground work is still required to estab­lish control points, but much of thiswork is replaced by the technique of

* Secretary of the Group Meeting.

aerial triangulation.4. Photogrammetric methods are abou t 40

per cent faster than the correspondingground methods, and there is less possi­bility of having observational mistakesin photogrammetric procedures thanthere is in ground procedures.

5. The accuracy of a first-order stereoplot­tel' in planimetry and height is about1 :7,000 of the flying height. The accura­cy of a second-order stereoplotter inplanimetry and height is about 1 :3,000of the flying height. The accuracy of anaerial triangulated strip is a function ofmany variables, the length of the stripbeing one of them.

6. For highway work, aerial triangulatedstrips of up to 10 models are recom­mended, although some strips may be aslong as 20 models.

7. The slotted-templet method of aerial tri­angulation is a special case of the moregeneral spatial triangulation procedure.It is 5 to 10 times less accurate thanspatial triangulation in a first-order plot­ter and is restricted to planimett-ic tri­angulation.

Discussion of the second question, "}Vhatare the main advantages of photogrammetry overclassical methods of field mapping?", "'as ledby Mr. Brantley. The principal items dis­cussed were as follows:

1. Medi um-scale maps are used for study­ing general location of the route, whilelarge-scale maps (200 ft. = 1 in., 5 ft.contours) are used for more detailedstudy.

2. For general route-location, photogram­metric means may cost as much as theclassical means for getting data. How­ever, the photogram metric method pro­vides a wealth of extra information formany other phases of the work.

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694 PHOTOGRAMMETRIC ENGINEERING

3. Information obtained by photogram­metric methods is generally more reli­able, although perhaps not as precise, asthat obtained by classical methods; thatis, photogrammetric methods may havelarger errors than classical methods, bu tthey have fewer mistakes (blunders).

4. It is easier to obtain additional field in­formation (e.g. cross-section data) byphotogrammetry than by classical meth­ods. Thus, photogrammetry is moreadaptable than classical work for re­location.

5. Photogrammetric methods are fasterthan classical methods.

6, Photogrammetry could have its greatestapplication in work for interchanges andbridges sites rather than in the generalalignment problem.

7. For the time being, accuracy should notbe reduced for the sake of time and ex­pense in photogrammetric work.

Discussion of the third question, "What isthe role of aerial photographs in the differentphases of highway design, and how and to whatextent can the highway design be mechanized?",was led by Mr. Raley. The principal itemsdiscussed were as follows:

1. Photogrammetrically-determined quan­tities in highway work are generally 1per cent to 2 per cent higher than fielddetermined quantities. For this reason,many contractors prefer photogram­metrically-determined quantities overfield-determined q uan ti ties.

2. In the past, photogrammetric work hasbeen checked against field work. Thispractice is questionable, however, sincemany photogrammetric-techniquesprovide more accurate results thanthei r corresponding grou nd- tech niq ues.In general, the ground-survey standardis much lower than the photogram­metric-standard,

3. Photogrammetric methods provide avery economical, fast, and accuratemeans for gathering data.

4. The electronic computer is a valuableaddition to photogrammetric methods.In order to have a good job done, ho\\'­ever, a lot of thought must be put intoorganizing the work beforehand, Elec­tronic computers are "high speed idi­ots" controlled by people who do lhethinking.

5. \Ve must use automation (photogram­metry plus electronic computation) inhighway engineering to keep up with

the automation 111 the automobile in­d ustry.

6. In reconnaissance, aerial photographyplays an important part in refining the"la-mile corridor." It can be used fordrainage analysis, soils interpretation,land use studies, and poten tial develop­ment studies. The electronic computerhas little use in reconnaissance work.

7. In the more detailed route locationwhere the horizon tal al ign men t shouldbe pinned down, large-scale maps (1 in.= 200 feet, 5 ft. contours) producedphotogrammetrically are al most in­valuable. They provide a means for an­swering a lot of design questions, andthey may be used to calculate earth­work quantities to within 5 per cent ofthe final design quantities.

8. Photogram metry com bi ned with elec­tronic computing has great use in thedesign phase of highway location. Ac­curacy is demanded in this phase, al­though no more accuracy than thatnecessary should be obtained. Super­fluous accuracy costs too much.

9. Photo interprelation can be used toguide the soil exploration program inhighway work, It does not eliminatedrilling, however, as it gives only sur­face data.

10. Photogrammetry and electronic com­putation can provide accurate position­ing of property corners. Photo mosaics\\'ith right-of-way boundaries and otherproperty lines drawn on them provideexcellent pictures of the highway right­of-way and adjacent property,

II. The earthwork estimate can be r;re­pared quickly by photograml11etric­electronic computer means. Photo­grammetry does the cross sectioning,and the computer analyzes the crosssections.

12. Photogram me try and electronic com­putation are valuable tools in highwayengineering work. However, they areonly tools. They remove much of thedrudgery from the engineer so thathe may do actual engineering work.

Discussion of the fourth question, "Howcan the geologic and soil studies be made bymeans of aerial photographs?", was led byProfessor Chryssofopoulos. The principalitems discussed were as follows:

1. Soil is a very important part of the high­way, since it forms the foundation uponwhich the road is built.

REPORT: APPLICATIONS TO HIGHW,\ Y WORK 695

2. Aerial photographs can be used to deter­mine what the parent material is. Vari­ous features visible in the photographicimage can be used to interpret the na­ture of the material lying on the earth'ssurface.

3. Aerial photographs can be used to locatenatural deposits or road-building ma­terials, many of \\'hich are hidden fromobservation on the ground.

4. Aerial photographs can be used to locate

sand dunes which move and so providedifficulties in highway construction andmaintenance.

5. Color tone in aerial photography can beused to distinguish between moist anddry soils. This provides an indirect wayof distinguishing course-grained soilsfrom fine-grained soils.

6. Aerial photographic interpretation doesnot eliminate ground work, hOIl'ever; itsu pplemen ts the grou nd work.

Kodak Panchromatic Negative Filmsfor Aerial Photography*

RAIFE G. TARKINGTON, Research Laboratories,Eastman Kodak Company,

Rochester, N. Y.

ABSTRACT: A review of the progress leading to the manufacture of the presently,wailable aerial negative films is given.

The results of investigations into the factors influencing aerial photographyand a technological improvement in photographic emulsions have led to theintroduction of improved aerial panchromatic negative films. The character­istics of these new films are indicated.

'l.X TORK on sensitized materials and equip­\' \' men t for aerial photography was started

at the Eastman Kodak Company beforevVorld \Var 1. During that war, improvementsin the sensitivity of photographic materialswere made so that, at the time of the Armis­tice, orthochromatic and panchromatic films,9t inches by 75 feet, were bei ng man ufac­tured (1). The most sensitive of these films,Eastman Panchromatic Aero Film, Hyper­sensitized, could be exposed at about 1/100second, f/S.6, through a Kodak Wratten Fil­ter No. 25. The K-1 camera was also designedat that time to use this film and is the grand­daddy of the large-format automatic aerialcameras of today (2).

Between the two World \Vars, much prog­ress was made in photographic science andtechnology so that, when the United Statesentered World \Var II, what is now calledKodak Super-XX Aerographic Film wasavailable for both reconnaissance and map­ping purposes. Also, Kodak Tri-X Aerograph­ic Film, having twice the sensitivity of Super-

RAIFE G, TARKINGTON

XX, was made available for use in night pho­tography or at other times of reduced illumi­nation. ] ust prior to the war, advances made incellulose chemistry provided a material of im­proved dimensional stability so that a safety

* Presented at the Society's 25th Annual Meeting, Hotel Shoreham, vVashington, D. c., March 8 to11, 1959.