RAnlOI'D D. SPE:\CER*

Forests Commission of VictoriaMelbol/rne, Victoria, Australia

Map Intensification from SmallFormat Camera Photography

35 mm and 70 mm photography taken from light aircraft provedto be more cost/effective than conventional ground surveys formap intensification.

bTRODUCTI01\

SII'CE THE 1840's photogrammetry has be­come a bas ic procedure tt)]" all types of

mappi ng, b'om broad coverage maps at smallseales to verv detailed contour maps of citiesand construction sites. Associated with thisincreasing use has been a continuous devel­opment of theory and instrumentation, theresult of which is a high degree of sophisti­cation with respect to aircraft, photographicequipment, and plotting equipment. Never-

being made, and for various reasons it isnecessary to prepare maps of these exten­sions as quickly as possible. A similar situa­tion exists tor private plantings and tor otherstates of Australia. In Victoria much of thismapping was based until recently on chainand compass survey, an expensive and time­consuming method.

Because a greater use of aerial photographswas an obvious means f(Jr streamlining thisprocess, attention has been given to the

ABSTRACT: In spite of great advances in theory and instrl/mentationill relation to aircraft, photography, and plotting, there exist manysitl/ations where simple eql/ipment can be l/sed to obtain aerialphotographs and to intensify map detail from them. The theory,techniql/es, and costs ofmethods that have been der;elopedformap­ping plantation extensions by l/sing vertical aerial photographyfrom 70 mm and 35 mm film format cameras in light aircraft aredescribed. The efficiency of the aerial method is compared withconr;entional field surr;ey techniques, and it is shol/;n that intensi­fied maps can be obtained which are at least as aCCl/rate for a costsaving ofup to 75 percent and a labor saving of86 percent. It is con­cluded that similar quick, simple, and low cost methods could bel/sed in many other applications, both within and ol/tside the forest­ry sphere.

theless, there still exist many situationswhere relatively simple equipment can heused to obtain aerial photographs and tomap hom them. The aim of this paper is toexamine such a situation: the mapping ofdetail in plantation extensions.

Substantial extensions to many state­owned plantations of Pinus radiata in thestate of Victoria in Australia are currently

• ~o\\' with the Town and Country PlanningBoard of Victoria, Australia.

development of simple, low cost, and rapidmethods for obtaining photographs with a70 mm or 35 111m camera. The methods thathave been developed, which are describedbelow, are intended to supplement but notreplace the major aerial surveys that arecarried out periodically tor the preparationof accurate base plans.

Because the major role of these small for­mat photographs is map revision or intensi­fication, a function also recognized by others{e.g., Lines, 1962; Cook, 1969; Zsilinsky,

697PHOTOGRAMMETRIC ENGINEERING AND REMOTE SENSING,

Vol. 44, No.6, June 1978, pp. 697-707.

698 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1978

1969; Klein, 1970), photogrammetric controlis less demanding. In addition, since onlymajor features are required, such as topog­raphy, new roads, tracks, and boundaries ofclearings, interpretation can be accom­plished from photographs at relatively smallscales.

CAMERA CONSIDERATIONS

The purpose of this section is to discusscamera requirements for supplementaryaerial photography and to illustrate some ofthe major differences between photographywith small format cameras and photographywith aerial survey cameras. In these illustra­tions discussion is confined to 70 mm and35 mm cameras because these are the mostcommon types available.

Any 70 mm or 35 mm camera with a goodquality lens and fast shutter speed (pref­erably down to 1/500 sec.) can be used to ob­tain supplementary photographs. However,cameras with motorized assemblies andlarge film capacity have obvious advantagesand are essential if access to the camera isnot possible during flight. It is also essentialthat the shutter should be of a type that willoperate at low temperatures, a danger whichis eliminated when shutters lubricated withsilicones are used (Zsilinsky 1969). It is alsoadvantageolls if the camera has the bcilityfor interchange of lenses.

The formats of 70 mm and 35 mm camerasare, respectively, 56 by 57 mm (2.18 by 2.25in.) and 24 by 36 mm (0.94 by 1.44 in.) andtheir focal lengths are normally 80 mm and50 to 55 mm, respectively. These lenseshave narrower fields of view than the lensescommonly lIsed in aerial survey cameras.Therefore, if comparable coverage is re­quired, photographs must be taken eitherfrom higher altitudes or with lenses of shOlterfocal length. For example, a 50 mm lens on

TABLE 1. LENS CLASSES IN AERIAL TERMINOLOGY

FOR 9-IN., 70 MM, AND 35 MM CAMERAS WHERE

FIELD OF VIEW IS THE ANGLE SUBTENDED BY THE

DIAGONAL OF THE FORMAT.

Focal Lengths (in mm) for

Lens Field ofDifferent Camera-Types

Class View 9-inch 70mm 35 mm

Narrow Less than 281 70 3860°

Nonnal 60 - 75" 281-232 70 -60 38 -31

Wide 75 - 100" 232-136 60 -34 31 -18

Sllper- Greater 88 22 12wide than 100"

e.g. 122"R.C.9

a 35 mm camera has a field angle of 41°12/(the angle subtended by the diagonal of theformat) compared to a value of 60° to 75° for"normal" survey lenses. Table 1 (afterSpencer, 1972a) flUther illustrates this point.Here the lenses of 9-in., 70 mm, and 35 mmcameras have been classified by focal lengthsinto the four lens classes given for aerialphotography by the American Society ofPhotogrammetIy (1966). The 9-in. format isused for comparison because it is now themost common employed for aerial survey.Thus, according to aerial tel111inology 70 mmand 35 mm cameras with lenses of focallengths exceeding 70 mm and 38 mm, respec­tively, are considered to be narrow-angle.

Note that the "field of view" in Table Irefers to the angle subtended by the diagonalof the format, which is the normal way ofexpression (HordeI', 1958). Although thisangle is of great importance when mountingthe camera so that its view is unobstructed,it is generally simpler and more meaningful,when making comparisons between theabove three camera systems, to consider theangles subtended by the axis of the format,i.e., the focal-Iength-to-picture ratio. In thecase of9-in. and 70 mm cameras which havesquare formats, the angle subtended by eachaxis is the same. However, with the rectan­gular 35 mm format the angles are different,and this affects comparisons relating toground coverage and image displacement.The first of these points is illustrated inFigure 1.

Figure la shows the relative areas of cov­erage obtained from the same height with9-in., 70 mm, and 35 mm cameras havingequivalent fields of view (i.e., equal anglessubtended by the diagonal). Thus, if thecoverage for the square formats is A, then forthe 35 mm format it is 0.9A.

Figures I b and Ie illustrate the cases forequal angles subtended by the axis. Thecoverage of the 9-in. and 70 mm cameras isstill the same and is designated A. Withequal focal-Iength-to-picture ratio, using thelongitudinal axis of the rectangular 35 mmformat, the coverage is 0.7A (Figure Ib)whereas for the transverse axis it is 1.5A(Figure Ie).

In all cases where large coverage is soughtwith small fonnat cameras, the scale of pho­tography must necessarily be small andherein lies a great disadvantage for manypurposes. Small format photography is notsuitable for jobs where it is necessary todiscern fine detail and still obtain broadcoverage because many flight lines andphotographs are required to cover a given

MAP INTENSIFICATION FROM SMALL FORMAT CAMERA 699

AIMS

The aims of these studies were-

• To develop operational procedures for ob­taining complete photographic coverage oflimited areas with a small format camera,light aircraft, and simple and inexpensivenavigational equipment.

• To use these techniques to obtain velticalaerial photographs for mapping boundariesof clearings, roads, and other features innew plantations.

• To analyse the costs of mapping with smallformat photographs and to compare thesewith the cost of ground survey techniques.

EQUIPMEl\T AND METHODS

AIRCRAFT A:'-JD PHOTOGRAPHIC EQUIPMENT FOR

70 MM PHOTOGRAPHY

In preliminary trials which are not report­ed here, the potentials and problems of usingsupplementary 70 mm aerial photographyfor plantation mapping were explored. Inthese trials photographs were taken with a70 mm camera which was mounted outsidethe open doorway of a Cessna 182 aircraft(Figure 2) and Hight line navigation wasbased primarily on unaided visual observa­tions.

The success of these trials ensured a con­tinuing use of the approach but, in order toimprove the accuracy of flight line naviga­tion and the comfcJrt of flying, a light air­craft was modifIed for internal mounting ofthe camera and a drift sight. The items ofequipment used in this system were

ing can be increased to permit good photocoverage with narrow-angle lenses, there isan accompanying advantage of reducedimage distOltions, a definite advantage whensimple mapping equipment is used. Also,because of the small format of 70 mm and35 mm cameras, enlargements provide themost practical form for mapping. The degreeof enlargement may be based on the ease ofhandling, annotation, and storage, or it maybe fixed so that the scale of enlargementsmatches the scale of existing survey photo­graphs or maps.

35 mm coverage = 0.9A

9-in. and 70 mm field of view.9-in. and 70 mm coverage = A

Field of view for 35 mm formatwith identical focal-Iength-to­picture ratio on longitudinalaxis.35 mm coverage = O.7A

9-in. and 70 mm field of view.

9-in. and 70 mm coverage = A

Field of view for 9-in., 70 mmand 35 mm formats.

_-++-+_ 9-in. and 70 mm coverage = AField of view for 35 mm for­mat with identical focal-Iength­to-picture ratio on transverseaxis.35 mm coverage = 1.5A

FIG. 1. Ratios of ground coverage obtained £i'omthe same flying height for 9-in., 70 mm, and 35 mmcameras. (a) Identical fields of view. (b) Identicalfocal-length-to-picture ratio for longitudinal axisof 35 mm format. (c) Identical focal-length-to­picture ratio for transverse axis of 35 mm format.

area. This point is clearly demonstrated inTable 2 which shows the ratios of area cover­age and numbers of photographs applyingto the three systems when photographs aretaken at the same scale. For example, to coverthe same area as a 9-in. photograph wouldrequire sixteen 70 mm or sixty 35 mm photo­graphs.

Thus, 70 mm and 35 mm cameras with"wide-angle" lenses are the most practicalfCJ!' complete coverage hom light, low perfcH­mance aircraft. However, if the aircraft ceil-

TABLE 2. COMPARISON OF RELATIVE GROUND COVERAGE AND NUMBERS OF PHOTOGRAPHS FOR AERIAL

PHOTOGRAPHY TAKEN AT THE SAME SCALE WITH 9-INCH, 70 MM, AND 3.5 MM CAMERAS.

Format Area Photos Along No. of Total

Canlera (mm) Coverage Run Runs Photos

35 mm 24 x 36 1 unit 10 6 60

70 mm ,56 x 57 4 units 4 4 16

9-in. 230 x 230 60 units 1 1 1

700 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1978

~

II

FIG. 2. In early trials, 70 mm photographs weretaken with a Vinten camera mounted outside theopen main doorway of a Cessna 182 aircraft, suchas in the dual-camera mount shown here.

• i\lodilJed Beechcraft i\lusketeer aircraft,• Aerial canlera,• Camera mount,• Control box and intervalometer,• 24 Volt D.C. power supply, and• Drift sight.

Three major modifications of the aircraftwere involved:

• A hole for internal mounting of the camera,• a second hole for mounting the drift-sight,

and• an additional inbuilt 12 Volt D.C. battery.

This battery was coupled in series with theaircraft battery for camera operation and inparallel lor recharging.

l'vlinor modifications to the aircraft in­c! uded removal of the front passenger's seatand modification of the back rest of the rearseat so that it could be removed during flightto improve access to the camera in the lug­gage compmtment.

The camera was a Vinten 70 mm fittedwith a lens of 3-in. focal length. It had a for­mat of 56 by 57 mm and was electricallyoperated. It was equipped with a roller blindshutter in the focal plane with speeds of1/500 or 111,000 second. The magazine,

FIG.3. Specially designed mount lor the Vintencamera and Beechcraft ~1usketeer aircraft. Themount has facilities for in-flight adjustment of tip,tilt, and swing. It also provides for easy access toand quick removal of the camera for makingchanges in exposure as well as changes of filtersand magazines.

which was loaded in a darkroom, had a filmcapacity oflOO It (approximately 500 frames).

The camera mount (Figure 3) was de­signed and constructed by Civil Aerial Sur­veys. It was supported at three points onrubber cushions. Veltical adjustment couldbe made at each of these points to level thecamera. Rotation about the vertical axis(swing rotation) also was provided to COI11­

pensate for non-parallelism between the air­craft axis and its track along flight lines. Thefacility for doing this cannot be seen in Fig­ure 3.

A modified F24 control box was used forremote control of the camera in the singleshot mode and for automatic "firing" atintervals ranging from 2 to 50 seconds. Italso has a fi'ame counter.

The drift-sight, an Aldis, had threefunctions:

• to determine the drift of the aircraft and theswing adjustment required on the camera,

• to bcilitate accurate navigation along eachflight line, and

• to determine the exposure-interval for ste­reoscopic overlap.

1

jI

MAP INTENSIFICATION FROM SMALL FORMAT CAMERA 701

SYSTEM FOR 35 MM PHOTOGRAPHY

The major 35 mm system was much sim­pler. It consisted of a specially designedmount that projected the camera through theopen doorway of the rear luggage compaJt­ment in a light aircraft, usually a Cessna 172or 182. This mount had adjustments for in­flight levelling but no adjustment for driftbecause the system did not include a driftsight. The camera could be retracted intothe aircraft for reloading film and settingexposure, but the film was advanced manu­ally in the in-flight position and the shutterwas operated by a remote control cable. Thecamera was an Asahi Pentax Sp II and wasfitted with a lens of 35 mm focal length,which simulated approximately the geome­try of a 9-in. camera with a focal length of8.8 in'. (223 mm). Because the system wasinexpensive and required no permanentmodi f]cation ofthe aircraft, anumber of unitshave been in use in Victoria, allowing flexi­bility in the timing of photography, choiceof air<:raft, and place of depalture.

In a second 35 mm system the camera wasmounted over a hole i;l the floor of the air­craft. The camera operator viewed the groundthrough the reflex system of the camera. Inthis way the camera perfonned some of thefunctions of a drift sight. The camera mountin this system had adjustments fCH tip and tilt,and modifications could have been made topermit adjustments for drift.

FLIGHT PLA:-<iXIKG

Conventional standards for flight planningwere adopted, with sidelap being approxi­mately 30 percent and forwardlap approxi­mate ly 60 percent. The former was to ensurecomplete photographic coverage of the areaand the latter was to permit stereoscopicstudy of each area.

The orientation of flight lines was deter­mined by two bctors, namely, the shape ofthe area to be photographed and the locationof easily recognizable landscape or culturalfeatures. vVhere possible, the beginning andend ofeach run (or extensions of these) weremade to pass over recognizable features. Asuitable plan was arrived at by trial anderror by using diflerent flight line orienta­tions, diflerent placement of the flight lines,and in some cases by reducing the flight linespacing.

\Vith the 35 mm camera on an externalmount, a drift-sight was not used, and flightIi nes were oriented to correspond with thedirection of wind and all photographic runswere made with the wind. This system great-

Iy simplified flight line navigation by elim­inating drift, although it did increase flyingtime. However, this was of little concern incomparison with the advantages gained. Thedirection of wind for the flying height wasobtained from a forecast, and it was checkedin a trial flight over the project area or overopen country where landmarks were con­spicuous.

A final flight plan for this method cannotbe drawn before the day of a flight becausethe wind direction is not known in advance.One system used to overcome this was todraw flight lines at the correct spacing on atransparent overla~' which can be positionedover the flight map or photograph on the dayof the flight. The other approach is to drawthe entire flight plan after take-off. In bothcases the plan is designed for a camera withthe long axis of its negative perpendicularto the direction of flight because it requiresfewer flight lines and permits larger errorsin flight-line navigation when side lap ismaintained at 30 percent.

The best "map" for flight-line navigationwas an annotated aerial photograph. For thispurpose photographs at a scale of 1:80 000proved very valuable. By taking appropriatecare, planning usually was done directly onthese photographs but, where doubt existedas to the degree of topographic displace­ments, the flight lines were drawn first on amap at an appropriate scale and then trans­ferred to the photograph.

Photography was usually taken from10 000 ft above sea level, which is the upperpermissible level for flying without extrasupplies of oxygen. Thus, for the majority ofplantations, contact scales of 1:28 000 to1:40 000 were obtained with the 3-in. lens.

Given suitable weather, another consider­ation in planning flights was to determinewhen photography could commence in themorning and when it should be terminatedin the afternoon, times which are a functionof solar altitude. For black-and-white pho­tography and where topography is not steep,a minimum solar altitude of 20 degrees is acommon standard (American Society ofPhotogrammetry, 1968). Because Kodak PlusX panchromatic 5061 film was used, thestandard of 20 degrees was adopted.

Maximum solar altitudes were also con­sidered in order to avoid the occurrence of a"hotspot", a bright area deficient in detail.The hotspot occurs in a photograph in anarea surrounding the point where a line join­ing the sun and the aircraft intersects theground. It is, therefore, more likely to appearat high sun angles and when cameras with

702 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSI G, 1978

wide-angle lenses are used. Its acceptibilityis related to the purpose for which the photo­graphs are to be used and to the propOitionof each photograph it degrades; hence, thescale and format are impoItant. "Vith 70 mmphotographs at the above scales, it is bestavoided.

Nomograms based on latitude, time ofyear,and limiting solar altitude were used todetermine the length of the photographicday, the position of the hotspot, and thetimes that the hotspot enters and leaves thearea of the photograph (Fleming, 1964;American Society of Photogrammetry, 1968).

Film exposures were determined with aKodak Aerial Exposure Computer (EastmanKodak, 1966) in which the input variableswere aerial exposure index, flying height,solar altitude, and condition of haze.

The films for 35 mm cameras have notbeen designed specifically for aerial photog­raphy, and the correct exposures for differ­ent conditions have been learned by experi­ence. An exposure guide for Plus X black­and-white film is given in Spencer (1974).

Exposure intervals for stereoscopic for­wardlap of photographs taken without theaid of a drift sight are determined fi'om thescale of photography, format of the camera,and ground speed of the aircraft. Spencer(1971) provides details of these calculationsfor 70 mm and 35 mm cameras, and intervalsfor a 35 mm camera with a focal length of35 mm have also been tabulated (Spencer,1972b, 1974). When a drift sight is used,these intelvals are determined in flight fromthe time an image takes to traverse a grati­cule in the sight.

FLYING PHOTOGRAPHIC MISSIONS

Successful navigation of the flight lineswithout a drift sight depends to a greatdegree on the skill of the pilot, whose job itis to bank the aircraft at the beginning ofeach run so that he can see the position ofthe run, and then to level the aircraft andset its course to fly along the run. A mirrorsystem is used to check flights over identifi­able pass points.

Visual navigation is used to locate the staltof each run, but navigation along flight linesis solely by instrument (the directional gyro)to achieve straight flight lines. If a run goesoff its course, it should be reflown ratherthan corrected in flight. When the drift-sightis in use, however, minor course correctionsare made by means of flat turns. Exposureintelvals for stereoscopic forwardlap in thiscase are determined in flight.

Even under good conditions the work

demands a high degree of pilot skill andconcentration. The pilot should be briefedin detail and trained for the work. His jobcan be made easier by good planning offlight-line positions which stalt and finishover recognizable points.

MAPPING TECHNIQUES

The mapping techniques employed were­(1) Mapping was from 6 by 6 in. prints

(i.e., 2.7x enlargements) at scales of 1: 10300to 1: 15 000, but most commonly at approxi­mately 1:11 900. This format was selectedbecause the scales so produced were readilyconveltible to the common scale of planta­tion maps of 1:7920 or 1:15 840. The formatwas also a convenient size for handling andannotation.

(2) Photographs were then examined ste­reoscopically, and various features withinthe effective area of each photograph weremarked with a fine-pointed ink pen of china­graph. These features included clearingboundaries, roads, creeks, ridges, and cadas­tral boundaries, as well as any other featureswhich would help to "tie in" the area beingmapped.

(3) Detail was then transferred to a topo­graphic base-map with the aid of a Zeissvertical sketchmaster. Th is is a monoculartransfer instrument which is of a portabledesign and facilitates superposition of thephotographic image onto the map. It accom­modates scale ratios between the photographand map of 0.4 x to 2.7 x, and it provides foradjustment of the photo plane to any posi­tion relative to the map plane. As a result,the scale throughout the photo projectioncan be varied, thus improving the scope forovercoming any lack of correspondence be­tween the photo image and the map. Theseadjustments provide the means to obtainaccurate results provided that the topo­graphic base-map is reliable and that care istaken to "fit" detail within points of control.

(4) When the draft map was completed itwas taken to the field to determine roadclassifications and distances from roads toplanting edges, as well as to check measure­ments and interpretations for doubtful fea­tures.

RESULTS AND DISCUSSION

PHOTOGRAPHY

By using techniques such as those de­scribed, some 8100ha of plantations werephotographed during 1971. These areaswere in seven localities and were photo­graphed during three separate missions. The

MAP INTENSIFICATION FROM SMALL FORMAT CAMERA 703

largest single area was 4050ha (5 by 8 km) ofestablished plantations, and this requiredsix sidelapping runs for complete coverage.The remaining 4050ha were extensions andonly these were subsequently mapped.

MAPPING

Errors in maps are of two types, metric(i.e., quantitative) and non-quantitative. Acommon but costly procedure for assessingmetric errors is to conduct detailed samplesurveys and then calculate the standarderror (root mean square error) of deviationsfrom the survey data (Thompson et ai., 1971).However, even with this approach there isan area of interpretation which must berecognized in order to avoid the rigid appli­cation of rules that do not reflect the purposefor which the map is prepared.

Non-quantitative errors are errors of inter­pretation other than metric origin. Examplesare the incorrect recording of species or yearof planting, or the incorrect classification ofroads. Although the bulk of this informationwas obtained from field checks or existingrecords, features such as the type of clearing(broadcast or windrow) and the direction ofwindrows were readily obtained fromphotographs.

In the present studies, resources did notpermit the calculation of standard errors.However, careful inspection of the maps, byemploying field and office checks, led to theconclusion that the maps intensified by thisprocedure were at least as accurate as mapsintensified fi'om normal chain and compasssurvey data. Factors contributing to thisconclusion were-

• Detail was transferred to topographic basemaps of a suitable scale and quality (whensuch maps are not available, the same re­sults might not be obtained);

• Photographs provided numerous controlpoints for referencing detail and "tying in"newly mapped areas;

• Irregular boundaries of uncleared areaswere more accurately defined on aerialphotographs, for example, boundaries ofareas reserved for special purposes such asflora reserves, fauna reserves, and gulliesfor the protection of water supplies (Fig­ure 4);

• The shapes of dense and complex networksof roads (Figure 5) were more accuratelydefined and referenced to topographic fea­tures on aerial photographs; and

• Photographs provided an accurate checkthat all areas had been accounted for, apoint of palticular importance in highlydissected country with many small butindividual plantation units.

The methods which have been describedalso afforded considerable savings of timeand costs.

ANALYSES OF COSTS AND TIMES

A summary of the costs is presented inTable 3 for the 70 mm photography and mapintensification of approximately 4000 hec­tares of plantation extensions in central andnorth-east Victoria. These costs were fornine project areas which were photographedin three missions. The costs were dissectedinto major components of photography, draft­ing, and field-checking. Costs per photo­graphic mission have been apportioned toindividual plantations in propOltion to theirarea and account for all direct costs includingsalaries of officers. The average per hectarecosts for photography and mapping areshown to be 12.2 and 29.7 cents respective­ly, thus giving a total map production costof 41.9 cents per hectare.

Table 4 is a summary of the major compo­nents of total cost, both in terms of dollars

,"'::~ 4f!# " ~--.;;;;:

J . "<.?~-;r--.

FIG. 4. Examples of 70 mm photographs (scale approx.l:32 000) employed for determining irregularboundaries of uncleared areas of native hardwoods retained for special purposes such as flora, fauna,and recreation reserves and gullies for protection of water supplies.

704 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1978

I

Ii!FIG. 5. Examples of70 mm photographs (scale approx. 1:32000) employed for mapping the dense andoften ilTegular network of roads in new plantations in hilly topography. Note the location of roads androad junctions in relation to topographic features, features that provide numerous control points formapping detail and the "tying in" of newly mapped areas on existing base maps. Note also the clear dis­tinction between areas with windrows and those without them.

and of percentages. Thus, we can see thatphotography accounted for 16 percent, air­craft hire 13 percent, and map-compilation71 percent of the total cost.

In order to compare the efficiency of theaerial survey techniques with the field sur­vey techniques, costs and labor inputs weredetermined for both methods and are pre­sented in Table 5. The values in this tableapply to the mapping of 365 hectares ofclearing in project area "G", an area 270kilometres fi'om the aircraft base and with acomplex network of roads and uncleared re­serves.

Costs of the photographic survey given inTable 5 are presented in two ways. In thefirst instance they are a record of costs whichwere incurred when the area was photo­graphed in conjunction with two other areas.In the second case they represent estimatesfor photographing the area as a single project.In the first case the mapping cost per hec­tare was 48.8 cents, compared with a valueof 79.0 cents for the second case and $1.97for the field survey technique.

The man-day requirements were also inthe same order, being 7 to 8 days for thephotographic method and 49 days for thefield-survey method. Thus, when the areawas photographed as pmt of a joint project,the cost of producing a map using the photo­graphic techniques was 25 percent of thecost for field survey methods and the laborrequirement was 14 percent. Had the areabeen photographed as a single project, thecost of the photographic techniques wouldhave increased to 40 percent of the cost ofthe field survey methods, but the labor re-

quirement would have increased only slight­ly to 16 percent.

These results clearly illustrate the value ofusing the aerial photographic techniques de­scribed above. The techniques have theadditional advantage of providing a detailedand permanent record in the form of photo­graphic images, which may be used in futurestudies of each area.

CONCLUSIONS

The mapping studies described in thispaper have involved the use of methodswhich are intended to supplement, but notreplace, the major aerial surveys that arecarried out periodically for the preparationof accurate base plans ofplantations. Indeed,accurate base maps are required for scalingwith the "sketchmaster" technique.

Specific conclusions from the studies are­(1) Small-format cameras in light, low­

performance aircraft provide a simple, quick,and low cost method for obtaining currentphotographs for use in mapping plantationextensions.

(2) 70 mm and 35 mm cameras with wide­angle lenses are the most practical typeswhen complete coverage is required fi'omlow performance aircraft. However, if theaircraft ceiling can be increased to permitgood photo coverage with narrow-anglelenses, image distOition can be reduced.

(3) Any 70 mm or 35 mm camera with agood quality lens and fast shutter speed canbe used to obtain supplementary photo­graphs, although cameras with motorizedassemblies and large film capacity have obvi­ous advantages. It is also essential that the

.' ..... I

TABLE 3. SU~nIARY OF COSTS FOR ~lAPPI~G 1970 A~D 1971 PLA~TATIO~ EXTE~SIO:-lS IN CENTRAL ANDNORTH-EAST VICTORIA USING 70 111m AERIAL PHOTOGRAPHS

Cost pcr hectare (cents)

Area (Hectares) Costs S'sDistance frol11 Total

Project Base 1970 1970 Photog- Field Photog- mapArea (km) Planting Clearing Total raphy Drafting Checking Total raphy ~Iapping cost

A 50 579 - 579 133 143 29 305 23.0 29.7 52.7B 180 418 527 945 58 233 46 337 6.1 29.7 35.8C 190 88 142 230 14 57 12 83 6.1 29.7 35.8

(+3,904) (240) - - - (6.1)D 110 497 648 1,145 70 283 57 410 6.1 29.7 35.8E 100 271 255 526 101 130 26 257 19.2 29.7 48.9F 190 - 203 203 39 50 10 99 19.2 29.7 48.9

(+203) (39) - - (19.2)G 270 - 365 365 71 90 18 179 19.5 29.7 49.2

PX Photography and mapping 1,853 2,140 3,993 486 986 198 1,670 12.2 29.7 41.9All photography - - 8,100 765 - - - 9.4

Comments:1. Photograph~ ti)1" the ahoH' proje<.:ts was completed in threl.:' llli:-.si()n~ and the total costs per photogmphil' llli ... sion h,\\'(' beell apPOltioned to individlwl plantation ... in propOltion to their arc;1.2. Costs fiJI" the photography arc ,Ictua] \"lllles. In the l.:a ... e of the ....econcl mission, the costs include phot()graph~'for all estahlished plantations ,H Arca C. totalling 3,90·' hectares. taken so that the

extent of sno'" <!il1nagl' could he determined. In the cast' ofthc:..' third mission, the~' include photography oJ'203 1lL'<.:tares of ro.lded hut as ~'et lI11cle;\!"l'd 1972 l'xtensions ,It :\rea F..3. Costs for drafting and field eheeking are estilll.tted ,It till' rate of fs2.5U and S.50 per thollsaml hectare rt;'specti\'(.. l~·.

.... Arca:-. for 1970 plantings art;' actual; those for uno dearing... are e .. tirnate" and coincide with the l'll:aring tar~eb l()I' each pbntation (Exeept lin' Area G where the aetual area is given).

.5. The per ha co:-.h l(u' Area :\ i:-. higher bee<lu:-.e the fir.;t alh:'mpt to photogmph this arca wa~ ;\balldoned due to lI11filvorahle e10ud eo\"er.

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706 PHOTOGRAMMETRIC ENGINEERI] G & REMOTE SENSING, 1978

TABLE 4. BREAK-DOWN OF TOTAL COST INTOMAJOR COMPONENTS FOR PHOTOGRAPHING AND

MAPPING 4000 Ha OF PLANTATION EXTENSIONS.

Cost in Percentage ofItem Dollars Total Cost

Photography 271 16Aircraft hire 217 13Map compilation 1,184 71

TOTALS 1,672 100

shutter be of a type that will operate at lowtemperatures.

(4) Enlarged prints provide the most prac­tical form of photograph for mapping. Thedegree of enlargement is based on the easeof handling, annotation, and storage, or itmay be fixed so that the scale of enlarge­ments matches the scale of existing surveyphotographs or maps.

(5) AnalYSiS of the major components oftotal cost for mapping 4 000 ha of plantationextensions showed that photography ac­counted for 16 percent, aircraft hire 13 per­cent, and map compilation 71 percent of thetotal cost.

(6) For an area of 365 ha located 270 kmfrom base the cost of intensifying a map withthe photographic techniques was 25 to 40

percent of the cost of field survey methods.The variation in cost depended on whetherthe area was photographed as part of a jointproject or as a single project.

(7) The man-day requirement for intensi­fying a map with the photographic techniquewas 14 to 16 percent of the requirement forfield survey methods.

(8) Photographs provide a detailed, per­manent, and quickly retrievable recordwhich can be used in future studies of anarea.

There are certainly many advantages to thesmall-format camera system in plantationmapping. The same methods could be usedwith similar benefits in many other applica­tions, not only in the field of forestry butalso in other fields.

ACKNOWLEDGMENTS

The projects desc:ribed have been con­ducted mainly for the Forests Commission,Victoria, but in pmt have evolved hom post­graduate studies at the School of Forestry,University of Melbourne. Assistance hasbeen provided in a variety of forms fromcolleagues in both organizations. In particu­lar, the author is grateful to Dr. J. A. Howardof the School of Forestry at the University ofMelbourne (now with the Remote SensingUnit of the Agriculture Department, F.A.O.,

TABLE 5. COMPARISON OF COST AND LABOR I~PUTS FOR MAP INTENSIFICATION BYFIELD SURVEY AND PHOTOGRAPHIC SURVEY TECHNIQUES FOR 365 Ha

OF PLANTATION CLEARING IN AREA G 'NHICH ISLOCATED 270 km FROM BASE.

Actual Photo Photo Survey asSurvey a Single Job Field Survey

Man Cost* Man Cost* Man Cost*days (Dollars) days (Dollars) days (Dollars)

Photography 1 71 2 180Prepare/

check!celtify map 5 90 5 90 5** 100

Field Survey 1 18 1 18 32 418Compilation!

plotting inDistrict. 12 200

TOTALS 7 179 8 288 49 718

Cost per ha 0.488 0.790 1.971

Percentage offield surveymethod. 14 25 16 40 100 100

>I< Inputs of enst afe not proportional to inputs of labor (man-days) because of variations in rates of pay a<:<:ording to the class of workperformed and variations in other cost factors.

*'" Che<.:king of field compilations and plotting is necessary before final certification of plans by the responsible oflkcr.

MAP INTENSIFICATION FROM SMALL FORMAT CAMERA 707

Rome), and ~/lessrs. V. C. Henderson, D. W.\iI. Paine, and W. D. Incoll of the ForestsCommission for their encouragement andsUPpOtt.

REFERE:-\CES

American Society of Photogrammetry. 1966. Man­ual of Photogrammetl1J, American Society ofPhotogrammetry, Virginia.

American Society of Photogrammetry. 1968. Man­ual of COlO1' Aerial Photography, AmericanSociety of Photogrammetry. George BantaCo., Wisconsin.

Cook, C. F. 1969. The use oflight aircraft in finestinventory and mapping. Woodlands Section,Pulp and Paper Magazine of Canada, .July 4,pp.69-74.

Eastman Kodak Company. 1966. Kodak AerialExposure Computer, Kodak publication RIO.

Fleming, E. A. 1964. Solar altitude nomogramsf01' aerial photography. S. and M. ProvisionalReport No. 64-3 Department of Mines andTechnical Surveys, Ottawa. 19 pp.

HordeI', A. 1958. Ilford Manual of Photograph!!,5th ed. II1'0 I'd Ltd. Essex. 725 pp.

Klein, W. H. 1970. Mini-aerial photography.jolll'­nal of Forestry 68, pp. 475-478.

Lines, .r. D. 1962. Spot photography for map revi­sion. Cartography, 4, pp. 135-139.

Spencer, R. D. 1971. Planning and executing aerialphotograph!! using 35 mm cameras. J-I.S. For­ests Commission, Victoria. 26 pp.

____ 1972a. Plantation management studiesfrom sllpplementar!! aerial photographs. Un­published ~I.Sc. F. Thesis, University on1el­bourne, 259 pp.

___:-- 1972b. Supplementar!! aerial photog­raphy with 70 mm and 35 mm cameras. ~vI.S.

Forests Commission, Victoria, Divisional Con­ference, \'Vangaratta. 11 pp.

_____ 1974. Supplementary aerial photo­graphs luith 70 mm and 35 mm cameras. Aus­tralian Forestry pp. 115-124.

Thompson, M. M., and G. H. RosenHeld. 1971. Onmap accuracy specifications. Surveying andMapping 31 pp. 57-64.

Zsilinsky, V. G. 1969. Supplementary aerial pho­tography with miniature cameras. Photogram­metria 25, pp. 27-38.

(Received October 18,1977; accepted February 27,1978)

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