358 PHOTOGRAMMETRIC ENGINEERING

Portland, Oregon, and the work was done with a K-17 six-inch focal lengthcamera at a shutter speed of 1/300, an aperture of F-8, with a plane speed of 135mph. The original fears of distortion due to inability of stopping motion at thisscale were unfounded and very clear photography with an extremely minutedetail of ground shapes was obtained. It was found after setting up models onthis job that stereoscopic perception on the river bottom to a depth of about 15feet was possible and that soundings 'could have been made by correcting forthe light refraction of the water.

Some difficulty was found in establishing ground elevations by multiplexalong the dikes above the tide flats due to the prevalence of heavy grasses. Toreduce this source of error to a minimum, notes were kept in the course ofground control work regarding the exact height of grasses in various portions ofthe area. As a result, the precision of the work was well within the limits as in­dicated for the job.

Obviously the procedure used is applicable only where the ground is notoverly obstructed by heavy vegetation or timber and where the topography ofthe surrounding country permits safe flying at elevations of 1,500 feet above theterrain. The cost involved for this type of work approximates! of the costs ofdoing the work with differential levels and plane table, and also permits mappingof areas such as mud flats and tide lands where it is impossible to carry outground instrumental work. The technique should have wide usage wherevergood leveling is required in open or cleared land where differences in elevationare not excessive.

A FUNCTIONAL COMPARISON OF STEREOSCOPICPLOTTING INSTRUMENTS

R. J. Sparling and J. V. Sharp, Bausch & Lomb Optical Co.

ON SEVERAL occasions, various organizations and individuals have con­tacted representatives of the Bausch & Lomb Optical Co. to discuss the

possibilities of our developing for manufacture, various photogrammetric andparticularly stereoscopic plotting instruments for aerial surveying. It hasseemed strange to some that we did not immediately embark upon developmentfor manufacture of each new photogrammetric instrument, its optics or othercomponents when presented for development. The reason may be simply foundin the fact that the number of problems and personnel required to develop aninstrument, even from an operating prototype to a manufactured instrument,are as multitudinous as those in developing the prototype. To develop suchinstruments for manufacture also requires that each instrument of a given typewhen manufactured must meet the same manufacturing specifications as toquality and function. Then only is the user of the equipment assured of con­sistent performance for each instrument he secures. Only then, also, can he safelybase economic commitments for funds to secure equipment and personnel tooperate a successful mapping organization. This latter continuity specificationis a major cost-often overlooked-in the manufacture of such instruments bysmall instrument shops, besides the usual costs of material, of labor, of factoryoperations, of engineering, of administration, of distribution, and of operatingcapital. There has been, likewise, a need expressed by several members of thePhotogrammetric Society for a readily available and compact summary of thefunctions of stereoscopic instruments, such information often being remote and

-

MAJOR FUNCTIONAL PROPERTIES OF STEREOSC

From Volume XIV _Number 3 1..8

Photo~mJ?1etric ~EngiDeenng rn

Based on the Follow­ing Major Published

Sources

AerialPhotography Design Functions Used Relative

Orienta­tion

ModelScaling

Ex­terior

Orienta­tion

Floating Mark and Related Design Plotting S

2019

PlottingDevice

18

Drive

17

Eleva­tion

Linkage

16

Floating DotMoves Vertically

By Motion of

lS

Type

14

CommonMotions

Pro­vided

131211109

DistortionElimination

8

Projection

51 6 I 74

PrintedMedium

3

PrintersUsed

2

CameraLens

Type ofPhotog­raphy

Instrument(In use or of

interest)

Functional A -B.B. TaUey, EngineeringAnalysis of Applications of Terres-

Stereoscopic trial and Aerial Photo-Plotting grammetry. PitmanPub-

Instruments by Iishing Co., New York,N. Y. -;;I -c::l";

R. G. Sparling and B -Manual of Photogram- :3_.~ -5 ~.g .sJ. V. Sharp of metry, 1944, Pitman i ~ 0$ is .. '. :! ~

Bausch and Lomb Publishing Co., New ~ . ol ~ '5.g ::s .~.!l 0.Optical Co. York, N. Y. '8 §... '0 ~ ~ ~ ~~ -I- ~~ ~

C= V. Gruber, Collected._ '.0 ~ -E .. ~ >. ~ '" .. fl ~ ,.:l-5Notes on Functions Lectures and Essays, ...:l fl :J ~ ~ 5 0 '0 .. ~.~ 5 ~ f--~ ~ ~ 5 0$ g..~

by Number in Article Chapman & Hall, Lon- ... ~.. oS .~ .~ .> ~ en .5 ~ :J ~ -E .. ~:a i:4 I!l...:l ~ &:l8. 8 5 ] ~ 8 ! :J 1;O,.:l ....don I:l ~ bO ~ I:l l>O 8 0$ .~ .I:l 8 <:5 > ~ 13 0 ~ a 0 &:l ""5 ol ~ 8 '" rn ~ .!l ;;; > -c::l a.s 0. ~-

Symbols defined D-Photogrammetric Engi- - .. ~ 5 - ~ ~ ....g .~ l ~z~.. ~ ~ ~ ... ~ - '8 ~ ! .....~ .g -:·S.~ ... ~ 'C =.!l t:3 E t g .. 13 l>O ~.g ~ ;§ ~ < ~ ~ I:l ~ ~ ~in Upper neering, The American ..13 g. ~ =3 ~ .. j ~ S> ~ ] ....8.~ ~ ~ -5 e _ :;; Pot ~ ~ ~ e ... }O$·... U ::I ~ ~ ,J:J ol I!l ,J:J.8 §. <1 J,l 5 'o..§ 13 '> .. :! -c::l ~ ....... =a 1! .s '';:: l.'! .. <1

right corner Society of Photogram- ~ ~ :3 § :; ~ :9 ] § 1l -m ~ l.'! ~ j ~ ~ ~ t ~ ~ .& ~ ~ ~ ~ .~'~ f£ ~ .~ ~ ~ §'S ~ ~ ~ ~ § ~ "5 1; tJ g. .Q 'g,;a § fr.~ l.'! ~ ~ 5 8 ~ ~ fr "§ "5metry &:l:> 0 u::S z::: ~ U Pi: ~ Pi: Eo< ~ ~ Pot ::s .:; Pot Pot "" 0 Eo< Pot Pot U Po<::S < ~ ...:l ~::S u:> Zoo Z...:l o::S::S rn::S Pot 0':; Z rn ~ Eo-< ~ ~ Pot UPot ~ rn rn8

.g(,)

As manufactured by §~

Holst-CahillStereometer

Brock & WeymouthPhiladelphia, Pa. IIv'I-I-1 -I v'1 v'13' to. 8t'

2

-, XI vi v'1-1 xlv'I-114'X17' II v'1-lvl-lvl Xlvi 0 1010 10 1I-1v'111111 -I-I-Iv II xl xl xII 21-1v'1-1-1-1-1-1-lvl-I-Iv'lvlv'10 II vl-I-I-I-Il to 1

ReadingStereoplotter

U. S. Coast & GeodeticSurvey 2IVI-I-1 vi vi Xl8t' -, XI-Ivl v'1 0 10 1v'\35'X3S' II v'1-lvl-lvl xlvl-Ixl xlv'II-Iv' 1111 -,- '-'v II xl xl xii 21-1v'1-1-1-1-1-1-lvl-I-lvl-I-Iv'1I -1-1v'lvl-11 to 1

BauersfeldStereoplanigraph

Carl ZeissJena, Germany 3lvlv'lvl vi vlv'll00 to 210mml v'1 xl-I xl xl vi vl-118X18 cmll v'lvl-I-lvl Xlviv'I xl xl x 11-1v'131 3 31-1v'1- 1121 xlv'11 2Ivlvlv'I-I-I-I-Iv'I-I-I-Iv'lvlv'10 1I-1v'1-1-1v'10.1 to8

HugershoffAero-Cartograph

G. HeydeDresden, Germany 4Ivlv'lvl-Iv'I-1125 to 210 mml v'1 X I-I x Ix 1v'1v'1-118X18 cmll v'lvl-lvlv'lx Ivlv' Ix Ix I x II-Iv' 13 I 3 31-1v'1-11 01 01 01121-1v'1-1-1-1-lvlvl-I-I-Iv'lvlv'101I-1v'1-1-1v'10.2to5H. WildHpprbrugg, Switzerland

ch & Lomb Optical Co.Rochester, New York

KelshPlotter

Instrument CorporationBaltimore, Maryland 71 v'1 -I -I -I vi v'18!' v'1 xl -I xl xl xl v'1 -19'X9' v'lvl-I-Iv'1 0 Ivlvlxl-I-II-lvI31 3 31- lv'- 21 Xlv' 11 vi 0 1-lvlvl-I-I-I-lvl-I-I-I-Iv'1I vl-I-Ivl-Il to 1

FerberScintillating Plotter

GallusParis, France 81v'1 v'1 VI -I v'1-1 ? v'1 xl-I xl-I v'1 ?I-I ? II v'lvl-I-Iv'1 xlvlvl xl xl x II-Iv' 1313 31- lv'- 01 01 0 ll- lvlvl-I-I-I-I-I-I-Iv'I-lvl-Iv'1I vl-I-Ivl-I ?

NistriPhotocartograph

O.M.I. S.A.Rome, Italy 91v'1-1-1-1 vl-118 ems oI XI-I xl Xlv'I 0 1-113X18emil v'lvl-I-Iv'Iv'I-lvl xl xl x 11-1v'131 3 31-lvl- 110101011 ll-lvl-lvlvl-I-I-I-lvl-I-lvlv'I-II-Iv'I-I-Iv'1 ?

SantoniStereo-Simplex

GallileoFlorence, I tal)' 101v'1 v'1-1-1 vl-165 to 85 cms I v'1 xl-I Xl-I? 1v'1-II0XI0cmll v'lvl-Iv'lvlvl-lvl xl xl xii -lv121 3

6

11-lvl-1I 21 xlv'112!vl-!-lvl-I-I-lvl-I-lvl-lvl-lv'nvl-I-lvl-1 ?PoivillierStereotopograph

S.O.M.Pl\.I'is, France lllvl v'1 v'1-1 vl-1125 to 300mmi v'1 xl-I xl-Iv'1 ?1-118X18cmll vlvl-Ivlvl xlvlvl xl xl x 11-1v'131 3 31-lv l-1I 01 01 01l21-1v'1-1-1-1-lvlvl-I-Iv'I-lvlv'I-II-Iv'I-I-Iv'10.2t05

SantllniStereo-Cartograph III

Gal1ileoFlorence, Italy 121v'1 v'1 vi vi v'1-ll00·to 2°Omml v'1 xl-Ix 1-1-1v'1-118X20emll v'1-lvlvl-lx Ivl x Ixl xlv'II-Iv' 1313 31- lvl- II 21xlv'1I 21-1v'1-1-1-1-1v'1v'1-1-1-lvlvlv'Iv'II-I-Iv'lv l- 1 ?

WildStereoplotter A-6

H. WildHeerbrugg, Swit7.erland 131 vi -I -1-1 v'1v'1 98 to 270 mml v'1 xl-I x Ix 1v'lvlvl9'X9' vlvl-Ivl-Ix Ivl-Ivl-I- II -Iv 13/1 II-lvi-II 11 01v'1I21-1v'1-1-1-1v'1-lvl-I-Iv'I-I-I-Iv'II-I-lvlvl ... 10.15to1.0

FourcadePlotter

Air-Survey-CommitteeLondon, England 141 vi v'1 vi-I vi? v'1 xI-lXI-I? Iv'- ? v'lvl-lvlvlxlvlvlxlxlxll-Iv'1311 1 I- Iv1- II 21 vi x II 2 I -Iv'1- 1- I-I - Iv' 1v 1- 1- Iv'1- Iv1- Iv' II v 1- I-I v I-11 to 1

K.E.K.Plotter

P.B.KailDenver, Colorado lSlvl-I-I-lvlv' none v'1 x 1x I0 1- 1- I-Iv' 19'X9' - 'vl-I-Ivlvl-I-I-I-I 0 IIvl-13·- 1 Iv1- Iv II 0I 0 I 0 II 2 I - Iv' Iv' 1- 1-1- 1- 1- 1- 1- 1- Iv' 1- 1- Iv' II - 1- 1v'1 v 1- 10.5 to 2. S

Mahan-WernstedtPlotter

H. C. RykerBerkeley, California 16Ivl-I-I-lvlv' none v'1 X I-I 0 1-1-1-lvI9'X9' -'vl-I-Ivlvl-I-I-I-I 01Ivl-13'- Ilvl-lv" 0\ 0 I 0 II 21-lvlvl-I-I-I-I-I-I-I-lvl-I-Iv' 1I-1-1v'lvl-10.2 to2.0

Cooks PlotterMultiscope Plotter

Harvard UniversityCambridge, Massachusetts 17I v l-I-I-lvlv' none vlX -, 01- 1- I-Ivl ? - 'vl-I-Ivlvl-I-I-I-I 0 Ilvl-1313 11-i- lv 01010 Il v l-I-I-lvl-I-I-I-Iv"-'-'-'- Iv' IIv 1- I-lvi-IUS to 1.5

Talley~tereocomparagraph

AbramsContour Finder

FairchildJamaica, New YorkAbrams Instrument Corp.Lansing, Michigan

181~

19Ivl-I-I-lvlv'

none

none

vlX

v'IX

- -0 1- 1- 1- 1v'II0·XI0·

-, 01- 1- 1-lvI8t'X8t·

---,_1-1111

-'-'vl-lvl-lvl-I-I-101Ivl-1111

-I-I-IV

_I_I-'V

01010

01010

v' IIv 1- I-Ivl-Il to 1

v' IIv 1- 1-lvl-11 to 1

OPIC PLOTTING INSTRUMENTS

stem ObservationMeasurement System Observation System Details illumination

SystemExtensionof Con­

trolPlot~g II Se~vice and

Operations MalntenanceAuxiliary

Equipment

Function

Symbols Used

(y') =applies(-) =not applicable(x) =not lequired(0) =not provided for(?) =information not available

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21 22 23 24 251 26 1271 28 11291 30 31 32 33 34135136 1 37 38 39 40 41 42 431441 45 46 1 47 48 I 49 50 51 RemarksSource:Volume& Page

olvl-I-I -ivil -1-1-lvl-I-I-lvlv'-

vlvl-I-lvl-II-lvl-lvl-I-I-lvlv'-

A-542 .8-52201 vi-I VI-I 01-1 xl-I-lvl-lvl-lvl-lvl-I-1 vivil vl-I-I-I-I-lvll 0 1-1-1-llvl-1 vi-II olvlvivi-ivil xl xlvlvlvlI1) Pencil Hand Operated C-162,236 1

II 2) Transformation from conic D-XIII, 2-257projection by spiral reduc-

O!vl-lvl-IOI-lxl-I-lvl-I-I-lvl-lvl-I-lvlv V-----V 0--- v-v-OVVV-V XvvXX tiongear 2A-489

V V - - V - - - - V V V - - V - V V - V - 0 V X V - - - - - V - V - - V V V - - - - V - V X X X V - Y - 0 V V V - V X X X X X C-345 3A-489

V V - - V - - - - V V V - - V - V V - - V V - - - V - - - - V - V - - ,I V V - - - - V - V X X X V - V - 0 Y V V - V X X X X X C-3~5. 4. 3 A-502

V V - - V - - - - V - - - V V - 0 - Y V - V - V - 0 - - - - V - V - - V V V - - - - V - V X V V V - V - 0 V V V - V X X X X X 3) 2Steps-2x and 6x D-XIII, 1-59 54) Projectors re-quire special A-224

V V - - V - V - 0 - V - - - V - V V - - - - V X V - - - - V V - - V - V - - - v V v - - V X X X - V - y V - - - - V V X X X X mounts C-500 6D-XIII, 1-12.1

Y V - - V - V - 0 - V - - - V - V V - - - - V X V - - - - V V - - V - V - V - V V - V - 0 - - - - V - y V - - - V - X X X X X D-XIV, 1-11 7

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A-516 8A-522('')HI 9

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V V - - V - V - - - V - - V - V 0 V - - - - V X V - - - - V V - - V - V - - ~/I-I-I-' ~/I-" 0 1-1-1-" -I JJ -II oLIJJJ -II xl xl xl Xl)(" 'v~uVV--V- ---VVV--v- --vvv--v---VV-v---vvv V-----V ---- V-v-V-vv-V XXXXX

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V V - - V - - - - V - - - V V - 0 V - V - 0 - V - 0 - -- - V - V - - V V V - - - - V - 0 - - - V - V - 0 V V V - V XX X X X

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6

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. , J

SYMPOSIUM ON PHOTOGRAMMETRIC TECHNIQUES-COMMERCIAL OPERATIONS 359

difficult to locate in photogrammetric literature. Such a summary should becompact enough to be of use for wall or desk-top reference.

As a result of both these needs, it was felt advisable to analyze the availablepublished literature together with published comments on this literature inorder to secure at leasta functional basis of comparison of stereoscopic plottinginstruments of current interest. This comparison, begun in July 1948, is limitedto those instruments which are concerned primarily with aerial surveying. Wehave also limited the list to instruments reported to be now in use, or of sufficientinterest, because of basic type, to include in this analysis. No attempt has beenmade to compare the accuracy or range of usefulness, as this is an exceedinglydifficult task. It was successfully attempted, however, by Mr. W. T. Pryor, ofthe U. S. Public Roads Administration, in the December 1946 issue of Photo­grammetric Engineering. We do'not agree with the limits he placed on Multi­plex System of instr.uments as now manufactured by Bausch & Lomb, butwe clo agree that, in his article, he made a splendid and accurate effort tomuster the then published available data and the opinion then existing. We,consequently, have encouraged articles to be written and the intensification ofefforts of Multiplex mapping organizations, to change this point of view; thisapplies particularly to mapping organizations engaged in producing completehighway maps in many states and countries, Such an article by K. B. Wood andS. B. Gross is published in this issue and describes 2 foot contour work with theMultiplex Projector.

In a similar manner, related to this paper, if any group or individual feelsthat its favorite instrument has in any way been misrepresented in the followinganalysis, an article is invited. Such an article, we have been assured, would bepublished in subsequent issues of Photogrammetric Engineering.

Operational tests have been reported, from time to time, on prototypes ofnew instruments as indicating excellent operating accuracy; unfortunately thesetests have been over areas of low relief. It is our belief that tests of such in­struments are open to considerable question, unless tested in rugged terrainfrom pictures taken at a variety of flying heights from 1,500 to 40,000 ft., thenow published range of practical flying. This will aid in indicating the fulloperational scope of the instrument. The use of accurate grids is also consideredan excellent indication of the performance of an individual stereoscopic plottinginstrument of a system, if properly interpreted. A statement of the residualradial distortion of the system is also an important consideration, as no system,in spite of claims, is completely free of small residual distortions. The distortionportion introduced by lens systems can be measured to within an accuracy of afew microns, and its effects on mapping accuracy are reasonably well established.These factors all aid in judging the potentialities of any new prototype in­strument.

Factors of operating convenience and operational fatigue for operators andsupervisors, whose time is a major item in mapping labor costs, are importantparticularly in the competitive situation which exists in mapping today. Easeof training new operators is also of particular importance.

In judging any instrument, it seems important for any purpose that it beclearly shown whether or not the major functions are performed by the proto­type instrument. With this object in mind, analysis of the lit~rature availablein this country has been reduced to a concise tabulation enclosed in this issue.Functional properties have been described in as few words as possible for thepurpose of compactness. Wherever possible, words have been used which aredefined in the Appendix of the MANUAL OF PHOTOGRAMMETRY (1944 pre-

360 PHOTOGRAMMETRIC ENGINEERING

L

liminary edition). Statements explaining the meaning of various functions arereferred to by function numbers in this tabulation and are listed as follows:

Major Functional Propertiesof

Stereoscopic Plotting Instruments

No. Function

1. Type of photographs the instrument accommodates (vertical, oblique, con­vergent, multilens, normal angle, wide angle).

2. The camera lens focal lengths limits used or applicable.3. The material the instrument uses (film negatives, glass diapositives, paper

prints) and printed by contact, reduction, enlarging, rectifying or trans­forming printers.

4. The size of photographs used.5. The interior orientation of exposure camera restored or taken into account

in the photogrammetric process.6. The principle of the design, based on central or parallel projection.7. The projection produced by optical or mechanical means.8. Total or partial projection of the image used in the plotting procedure.9. Means by which the distortion of the camera lens is minimized.

10. The relative orientation of photographs permit correct coincidence settingwithin the entire model area.

11. Number of linear and angular movements which are provided for relativeorientation.

12. Means by which the scale of the optical model can be changed adequately.13. The ratio between horizontal and vertical model scale is constant.or variable

during operation.14. Common motions provided to rotate the optical model or the plotting table

for exterior orientation purposes.15. Measuring marks, opaque or luminous, are employed.16. Elevations measurements are made by displacements of the floating mark,

screen, the model surface, the plotting base, the plotting surface, individualimage, or by the mechanical movement of optical elements.

17. The measuring marks or individual photographs are jointly moved duringthe process of measurement or they are individually connected by a separatelinkage.

18. Tracks and gear drives of a rectangular coordinates system are provided forthe real or apparent movement of the floating mark, or this movement ofthe floating mark is hand controlled.

19. The plotting device consists of a simple pencil arm, a coordinatograph, or apantograph linkage, which is built in, or separate part of the instrument.

20. The range between model scale and mapping scale.21. The delineation of contours or profiles can be followed in continuance.22. The vertical measurements recorded on the map are contours'or form lines.23. The plotting is drawn in orthographic or conic projection.24. The viewing system consists of looking at the model directly, through a

mirror stereoscope, a set of magnifiers, or a binocular telescope.25. The Porro-principle of measurement is applied.26. The centers of perspective of observation of image detail are fixed or variable.27. The photographic images are viewed orthogonally.28. The stereoscopic or the flicker principle is applied.

SYMPOSIUM ON PHOTOGRAMMETRIC TECHNIQUES-COMMERCIAL OPERATIONS 361

29. Two image views are interchangeable at the observer's eyes.30. The pictures as observed through the viewing system are erect and direc­

tionally unreverted , or reverted.31. The magnification of the viewing system is produced by telescopic or pro­

jective means, but is fixed.32. The magnification of the viewing system is produced by telescopic or projec­

tive means, but is variable.33. Scale differences of conjugate images are or are not balanced in observation

systems, in the projective system, or in using another instrument.34. Results of measurements vary with the location of the pupils of the eyes.35. Results of measurements change with the variation of inter-pupillary

separation.36. The observation method (or system) requires accommodation of the eyes to

finite distance.37. Photographs or their images and floating marks or their images are invari­

ably viewed in common planes.38. The orientation of rays emerging from the exit pupils of the observation

system or the direct observation of images require parallel, convergent, orvariable position of the eye axis. .

39. The photographic detail and the floating mark are observed at critical focus.40. Artificial lighting required is white or dichromatic, and if white, constant

or flickering.41. Filter spectacles are needed for image separation.42. Illumination of image by optical or reflective means or by direct diffusion.43. Mechanical means are provided to extend instrumental control.44. Resetting of orientation data is required in extending control.45. Optical and 'mechanical reversions of movements are required in extending

control in alternate models.46. Several persons can observe the floating mark simultaneously.47 Several operators can do plotting work simultaneously.48. The instrument is portable or stationary.49. Service adjustments are necessary with each reassembling.SO. The light source used is an arc or filament type.51. Specially designed auxiliary equipment needed in the system of mappmg

in addition to standard contact printers.52. Remarks.53. Source of information in literature. (See symbols on left corner of chart.)

Other factors in considering stereoscopic plotting instruments are the collec­tive effects of approximate solutions of true design. Often we read that this orthat instrument will perform satisfactorily with one or more of the following"If's":

If the plane altitude is nearly constant.If the photographs are nearly vertical.If the terrain is nearly flat.If an existing map of the terrain is nearly as good as the one to be made.If the lens is nearly free of distortion.If the eyes are held nearly fixed.If the interpupillary distance of all observers was nearly constant.If the point of projection is nearly at the principal point.If the photographic image supporting surface is nearly flat.If the instrument orientation is nearly exact.

362 PHOTOGRAMMETRIC ENGINEERING

If the machine is mechanically maintained nearly precise.If the photographic prints are nearly stable.

These are a few ·of the dangerous "if's" to be considered in designing andusing stereoscopic plotting instruments. We agree that anyone "if" may beproven to have "negligible" effect in mapping. But, failure to consider the col­lective effects of al1 the "if's" and the setting of operating tolerances on the"nearly's" can result only in an assurance of operating difficulties in map pro­duction. We would not do justice to our present and future users by developinga photogrammetric instrument for their use, which does not consider all of thesefactors collectively.

Another important item not to be overlooked in comparing mapping in­struments, is information on whether an instrument which has been purchased,has been put in operation, and then set aside to be displayed in operation onlywhen visitors are shown through, on a tour of a mapping organization. Informa­tion as to the extent to which an instrument is being used, is often difficult tosecure, but is worth seeking in comparing stereoscopic instruments.

Final1y, in conclusion, when using such a tabulation as a basis for judgingthe value of any instrument for use, or for development, or for manufacture, eachfunction needs to be considered and clearly understood in regard to its effectson mapping accuracy, operating convenience and maintenance, and the collec­tive effect of all these factors on the ultimate factor-the final cost of thespecified map to the purchaser and user of that map.

REPORT OF NOMENCLATURE COMMITTEE

A. O. Quinn, Chairman

The American Society of Photogrammetry is in the process of revising the "MANUAL OFPHOTOGRAMMETRY." This important book contains a complete list of symbols and nomenclatureused in the science of photogrammetry. Since the original compilation of these data, a number ofnew terms have come into common usage and several of the terms probably need revisions andclarification.

In order to further the science of photogrammetry, the Scciety feels that it is absolutelyessential to standardize our non:enclature. All groups using aerial and terrestrial photographsshould use common expressions in the exchange of ideas and practices in photogrammetry.

The Nomenclature Committee of the Scciety has been charged with the res{:onsibility ofreviewing, revising and completing the symbols and nomenclature used in this country, Canadaand South America. To accomplish this most important task, the Committee is contacting thevarious commercial and government organizations using photographs, to enlist their aid in thestandardization of photogrammetric terms. In addition, the Committee requests the assistanceof every member of the Society. This job, once completed, will be a great contribution to allagencies and will do much in furthering the exchange of ideas and the training of new personnel.

The Committee would greatly appreciate the cooperation of each member of the Society inreviewing the present list of nomenclature as found in the "MANUAL OF PHOTOGRAMMETRY." Anote or letter should be sent to the Nomenclature Committee at the Society's address in \Vashing­ton.

MANUAL REVISION CO'MMITTEE

Letters have been forwarded to individuals or organizations requesting monitoring of thevarious chapters of the new MANUAL OF PHOTOGRAMMETRY. Acceptance has already been recievedfrom 75%. Those contacted have been very cooperative. Manuscript deadline has been tentativelyset as April 15, 1949.