THE PI PICTURE IN 1955*

Dr. Robert N. Colwell, School of Forestry, University of California,Berkeley, Calif.

E ACH speaker on today's symposiumhas labored long and thoughtfully in

order to distill into the few minutes allottedhim certain concepts on which he mighthave spoken for several hours. Thereforesome people might consider it quite pre­sumptuous of the enthusiast who selectedthe title for my paper and who wrote theabstract of it, to aI;lnounce that in "5 to 10minutes" I would provide "a criticalanalysis of the papers and discussion pre­sented at this annual meeting." Obviously,any such brief attempt to interpret thePI picture in 1955 must assume the formof a "flash" or "summary" report. There­fore, my interpretation will be limited tothe listing of a few salient features,grouped under three main headings; Re­search, Training and Production.

RESEARCH

Judging from the papers presented atthis Annual Meeting, current researchneeds in photo interpretation can begrouped under a few major headings aslisted below:

1. THE NEED FOR MORE AND BETTER PHOTO

INTERPRETATION KEYS

The fact that more than half of today'spapers have dealt with keys is indicativeof the importance ascribed to them in ourcurrent PI research effort. At the sametime, there seems to be a much clearerunderstanding now than formerly, thatkeys are not advocated as the cure-all toevery photo interpretation problem. Withthis point established, certain critics seemmore willing to acknowledge that properlyconstructed keys can often serve a veryuseful purpose. But such acknowledg­ment, even at this late date in the PI keysprogram, strikes me as being largely apresumption on the part of keys makersand a belated concession on the part oftheir former opponents.

Very little objective testing of the effec­tiveness of keys has been performed to

date. Certainly such testing should beconducted soon, as advocated by Dr.Young. Thereby we should be able notonly to demonstrate more convincinglythe value of keys, but also to resolvemany of the points of variance, expressedby today's speakers, as to the most suit­able form of key-mechanical vs. textual,associative vs. subject, and dichotomousvs. integrated-selective.

2. THE NEED FOR A BETTER SELECTION OF

PHOTO INTERPRETERS

Two important aspects of this problemhave been discussed. The first relates tovision testing of the photo interpreter, asdiscussed in Dr. Rabben's paper, "TheEyes Have It" and in Mr. Moessner'spaper, on "A Simple Test for StereoscopicPerception." As Dr. Rabben pointed out,there is no single vision test that is com­pletely adequate in this regard, since thephoto interpreter needs more than merestereoscopic acuity. Among the otherrequirements which he mentioned are:good distance vision, acceptable nearvision, good reserves for accommodationand convergence, good extra-ocular mus­cle balance, and the visual capacity tomaintain an exacting search for smalldetails. A person having a very high ratingin one of these vision tests, might proveon further testing to have the poorestover-all vision characteristics from the PIstandpoint.

A second aspect was presented in Dr.Whitmore's paper entitled "ManpowerJor Military Photo Interpretation." Thehighlight of his paper is that this countryhas an adequate number of competentearth scientists available to fulfill ourmilitary photo interpretation require­ments for terrain analysis, even in theevent of total mobilization. But would oursystem of selection and assigment of per­sonnel result in the proper placement ofsuch experts in the event of another na-

* This isa part of the Symposium 011 Photo Interpretation Key~ held on March 8,1955 duringthe Society's Annual Meeting.

720

THE PI PICTURE IN 1955 721

tional emergency? This question requiresa negative answer unless recent majorchanges (actual changes, not merely theoret­ical ones) have been made in the system,unbeknownst to the present speaker.

In addition to the above, other criteriafor selection of photo interpreters mightwell be developed, based on the individ­ual's powers of observation and imagina­tion, his powers of judgment and his over­all mental acuity.

3. THE NEED FOR A RE-ALLOCATION OF

FUNDS TO PERMIT MORE RESEARCH ON

THE CIVIL ASPECTS OF PHOTO INTER­

PRETATION

While this need was not mentioned byany of today's speakers, it is a very realone. The simple fact is that military organ­izations now control, directly or indirectly,most of the funds currently available inthis country for research in photo inter­pretation. As a result, non-military agen­cies such as universities, the National Re­search Council, and various branches ofthe Departments of Agriculture and In­terior, frequently must turn to theDepartment of Defense for funds withwhich to perform photo interpretationresearch. This arrangement often (but byno means invariably) proves unsatisfactoryto both the military and civil parties tothe research contract. For example, themilitary conti actor, under such an arrange­ment, often bemoans the fact that a PIcontract \vith a university results in anend product which reflects so largely theacademic or "ivory tower" approachas to have little direct military application.Conversely, the university scientists whoare party to the same contract may be sofrustrated by problems of military securityand so unaware of what the military re­quirement really is, that their product isdoomed to mediocrity, even if some of thefinest intellects in the nation are workingon it.

It is an excellent tribute to some of thepeople in this audience that the Depart­ment of Defense has seen fit to allocatesizeable funds for much-needed research inphoto interpretation. But it is unfortunatethat the military is so predominant in thecontrol of PI research funds in this coun­try that most civil research in PI is sub­servien t to it.

4. THE NEED FOR A QUANTITATIVE AND

QUALITATIVE EVALUATION OF THE PHOTO

INTERPRETATION SYSTEM

As stated in Dr. Young's paper, there isa need for evaluating the present accuracyand efficiency of all phases of the photointerpretation system in terms of its usualend product-the PI report. Only by sodoing can we recognize the weakest linksof the chain and develop logical means ofstrengthening them. Until thi;;; is done wewill continue to attack the over-all prob­lem on a piece-meal, hit or miss basis andwill be swayed more by catch phrases andwitty analogies than by valid reasoning.Just one example will be cited to illustratethis point:

At one of our Society's Annu.al Meetingsa few years ago, my friend Amrom Katzhad this to say. "This matter of photo­graphic interpretation strikes us as beinga very much unbalanced situation, where­in we may take a million dollar airplane, ahundred thousand dollars worth of cam­eras, a half dozen rolls of film, one of which(for the K-40 camera) is going to costabout $400 ... we take off on a veryhazardous mission in the sense of militaryand social economics ... when the photo­interpreter gets around to abstracting theinformation he uses a 10 cent magnifyingglass. The numerous reasons for thistremendous disparity between reconnais­sance equipment and interpreter's equip­ment are simultaneously operational, his­torical, technical and illogical. ... I t ishoped that before too long proper balancewill be restored."

It may very well be that we are muchin need of a better stereoscope for inter­preting aerial photos. But I submit thatthe reasoning cited above is specious andI would be willing to bet that a man assharp as Amrom Katz had his tongue inhis cheek when he wrote those words. Butfrom Berkeley, California to Delft, Hollandand from PI supervisor to peon, theargument is still advanced that surely wemust need a better stereoscope simplybecause present day stereoscopes con­stitute a disproportionately inexpensivelink in the photo interpretation chain.Since the end product of the PI effortusually is a report, might we not arguewith equal logic for a very costly pencilwith which to write that report?

722 PHOTOGRAMMETRIC ENGINEERING

At the expense of repeating my pre­viously published views on this subject Iwill again side with the biologist Mitscher­lich. Nearly 100 years ago he observed asimilar series of links in the biologicalchain and wrote: "When a biological proc­ess is conditioned as to its rapidity by anumber of factors, the increase in rateproduced by unit increment of any .lack­ing factor is proportional to the decrementof that factor from the optimum." View­ing this matter more realistically, then,it would seem that we should strive, now,for improvements at every limiting linkin the photo-i'nterpretation chain,* withthe hope that each improvement will in­crease the accuracy of the final informa­tion derived. At the same time in allocat­ing our over-all research and developmenteffort in the photo-interpretation field, wewould do well to allocate our energies to­ward the improvement of any limiting fac­tor in direct proportion to the decrementof that factor from the optimum.

The problem of determining the "dec­rement of each factor from the optimum"is a tough one, but how can we help butagree that a logical step toward solving itis to implement Dr. Young's proposal fora qualitative and quantitative evaluationof the photo interpretation system?

TRAINING

As in the case of research, the trainingaspects of our PI picture in 1955 can beinterpreted and reported upon under a fewmain headings as follows:

THE ACCELERATION OF TRAINING IN CIVILAPPLICATIONS OF PI

During this post-war decade, whilemilitary PI training first was in a declinebecause of demobilization and thenreached a relatively stable state, civil PItraining has grown quite remarkably incertain areas. For example, at the end ofWorld War II there were only 2 or 3schools in the U. S. where a student couldreceive any formal training in photo inter­pretation for forestry purposes. Todaysuch a course is required for graduation inthe majority of our forest schools, and is

* Those interested in one attempt to analyzethe various links in the PI chain are referred toa paper presented at our PI symposium lastyear entitled "A Systematic Analysis of SomeFactors Affecting Photographic Interpretation,"PHOTOGRAMMETRIC ENGINEERING, June, 1954.

offered as an optional course in most ofthe remaining schools. A similar situationprevails in other professions which employphotos extensively. In addition, specialPI field schools and "short courses" arebeing offered to various types of profes­sional men who can afford a few days inwhich to learn PI techniques that mightprove useful to them in their daily work.

SPECIAL SYMPOSIUM ON TRAINI G

Perhaps the most significant develop­ment at this Annual Meeting from thestandpoint of training is the special sym­posium on "Education in Photogram­metry" which is running concurrentlywith our PI symposium. Training in allaspects of photogrammetry, including PI,are being discussed at the symposium.Accordingly, those interested in the train­ing aspects of PI would do well to readthe proceedings of that symposium in thisissue of PHOTOGRAMMETRIC ENGINEERING.

PUBLICATION OF THE JOINT PHOTO INTER­PRETATION HANDBOOK

Work on this handbook has been pro­gressing for the past several years. Itsissuance within the past year representsthe first time since World War II that anup-to-date handbook has been availableto PI personnel in the armed forces. It isexpected tHat the value of this handbookin our military PI training programs willbe very great, indeed. One feature of thePI handbook, in contrast with the previousones, is the relatively infreque'nt use ofphotographic illustrations. This seemingincongruity is explained by the fact thatthe publication of an increasing numberof military PI keys and related documentsprovides adequate photographic supple­ments to the basic manual.

PUBLICATION OF A MANUAL ON METRICALTECHNIQUES

During the past year, both military andcivil versions of this manual have beenpublished under the respective titles:"101 Keys to Metrical Photography" and"Photographic Measurements-lOl Prob-

AUTHOR'S NOTE: For a highly significantanalysis of civil and military PI training seeBoston University Technical Note 119 "AComparative Analysis of Curricula and Tech­niques Used in the Training of Photographic

_ Interpreters," by S. A. Custer and S. R. Mayer.

THE PI PICTURE IN 1955 723

lems and Solutions." Photo interpretershave long been criticized for their reluc­tance to make photo measurements whichwould support their qualitative interpre­tations. To the extent that such criticismsare valid, this manual should fill a realneed, and therefore merits a brief reviewhere. The comprehensiveness of the man­ual is indicated by the fact that it surveysthe field of photogrammetry, broadlydefined, from shutter calibration to stere­oscopy, from lens optics to relief enhance­ment, and from image motion compensa­tion to high altitude stereo techniques.Like all manuals, this one has certainlimitations. In this case the limitations aremainly organizational. No logical remedyto this problem presents itself because ofthe tremendous breadth covered by themanual and the numerous inter-relation­ships to be found among its 101 problems.

This manual in either its military orcivil form should be a welcome additionto the library of any photo interpreter,because it is of great potential value as atraining aid for the making of quantitativeinterpretations. But until the PI thorough­ly familiarizes himself with its contents andorganization, the manual may lie there onthe shelf with its pages unblemished bythe pencilled notations and dog-earedcorners that are a true measure of its use­fulness.

PREPARATION OF A SOCIETY-SPONSORED

MANUAL OF PHOTO INTERPRETATION

This was already reported upon by thepresent speaker earlier today so will not bedescribed again here. Its potential signifi­cance in relation to the training of PI'sis obvious since the most authoritativeworkers in various aspects of PI, both hereand abroad, are being asked to contributeto it.

PRODUCTION

From the military PI standpoint, pro­duction, other than that already alludedto today, will be regarded as having asecurity classification beyond the purviewof this audience.

From the civil PI standpoint, however,noteworthy production can be reported ineach of several fields:

GEOLOGY

According to Robert L. Anderson ofGeophoto Services, in 1954 over i million

square miles of Photogeologic mapping byvarious companies and government agen­cies was completed in this country andforeign areas. This eyebrow-raising figure(equal to more than a fourth the area ofthe United States) has been accomplishedby a mere handful of personnel. Thesephotogeologists have covered more area, inless time, and at less cost, than anyonewould have considered possible a mere tenyears ago. Largely as a result of their ex­cellent work, mineralogical discoveries ofmany kinds currently are being made at arate heretofore considered unattainable.

FORESTRY

In California alone during the pastyear, experienced photo interpreters haveclassified nearly one million acres of tim­berland as to size class, stand density andvegetation type. The detail with whichthis work has been done is indicated bythe fact that each timber stand coveringmore than 10 acres has been classifiedand mapped individually in all cases whereit differed materially from surroundingstands in any of the above three respects.When one recalls that on the 1/20,000scale photography with which this classi­fication is done, a 10-acre ground area isrepresented by a square less than 0.4 inchon a side, he will recognize this as one moreinstance in which detailed photo inter­pretation by highly skilled personnel isproving of great practical value on anactual production basis. While Californiahas been somewhat more progressive thancertain other regions in the photo classifi­cation of its timber resources, similar workhas been performed, or soon will be, inmany other parts of the country.

SOILS

The mapping of soils in wildland areashas only recently advanced from the re­search stage to the production stage. Inthe past year, for example, approximately600,000 acreas of wildland soils classifica­tion has been performed in California byskilled photo interpreters. The success ofthis project has resulted in the formulationof plans for expanded production in thenear future both in California and else­where.

GEOGRAPHY

Depending upon the definition of geog­raphy to which we subscribe, recent PI

724 PHOTOGRAMMETRIC ENGINEERING

production in this field has been little orgreat. If one considers that geographymeans literally to "write about the earth,"then photo interpreters have been activeindeed this past year--not only those justmentioned under the headings of Geology,Forestry and Soils, but many others aswell. Among these are such men as Mat­thew Witenstein, who spoke this morningon urban area an~lysis-and those en­gaged in the production of PI keys, aboutwhich we have heard much today. Others,such as Professor Kirk Stone who is cur­rently so active in the photogeographicinterpretation of Arctic areas, have beenhighly effective producers in this field.

If, on the other hand, we agree withthose who define geography as "the studyof landscapes, regions, distributions orof the synthesis of the national and socialsciences" then a different conclusion isindicated as to the productiveness of photointerpreters in this field. In this case wewould be inclined to agree with our panelmoderator Dr. John Roscoe who, at a re­cent AAAS meeting berated such geog­raphers rather unmercifully for failing touse aerial photos as intensively or exten­sively as they should.

Perhaps the closest approximation tothe truth in this regard is a recent state­ment by our Society's National President,Art Lundahl, as follows: "The full impactof the importance of photogeography hasnot yet been recorded and we are just be­coming generally aware of the possibilitieswhich it offers in combination with otherearth science data, in the economic, scien­tific and cultural development of man."

SUMMARY

If I have correctly interpreted the PIpicture in 1955, there has been muchsignificant progress recently in the re­search, training and production aspects ofPI-progress for which we can justly beproud. At the same time, in each of theseaspects there remain many problemswhich should challenge a photo interpre­ter's stereoscopic and mental acuities tothe utmost for a good while to come. Thisis a healthy situation-one which shouldassure a bright future for every able bodiedPI, and one which should permit us toconvert even the remaining skeptics whoinsist that "PI" stands for "peeringidiot," into potential customers of our serv­ic.es, along with all the rest of mankind.

CLOSUREDR. ROSCOE: We have had the largest turnout of any of the technical panels and,

in fact, of any of the general sessions to date. Keeping this in mind, one can see there willbe a genuine need indeed for the Manual on Photo Interpretation. AIl of you who maybe called on by one of the author-editors should consider seriously your contributing inyour field. This is a product of the Society as a whole and the help of everyone is needed.

NEWS NOTE

KODAK ISSUES PAMPHLET ON DI­MENSIONAL STABILITY OF PHOTO­

GRAPHIC FILM

A new Eastman Kodak publication,"Dimensional Stability of PhotographicFilm," is available for distribution.

Dimensional stability of sheet film is ofinterest in a number of applications suchas reproduction of mechanical drawings,topographic maps, color separations, andvarious other graphic arts and industrialuses. The leaflet is intended to explain why

photographic films change size and toprovide some dimensional stability datafor both cellulose ester and polystyrenebase film sheets. The theory and types ofexpansion and shrinkage are discussed withsuggestions given for handling film to mini­mize size changes. Also included in theleaflet is a table of average dimensionalchange values for Kodak Sheet Films.

Copies of the leaflet are available with­out cost from the Sales Service Division,Eastman Kodak Company, Rochester 4,

ew York.