776 PHOTOGRAMMETRIC ENGINBERING

field and in the office. The profession is developing collections of photographsfor teaching and research purposes.

The success of such a program is hampered by the fact that geographers,generally, are not in a position to broaden their experience in the developmentof techniques by using photographs which are made specifically for geographicpurposes to geographers' specifications. Photographs, in almost limitless num­bers, are available for geographic use and their contribution to the developmentof field techniques and interpretation procedures is unquestioned and obvious.The geographer, however, has special needs which are not commonly met andit is not unreasonable to assume that he can best develop methods which aregeographically effective if he be afforded the opportunity of experimenting withphotography that is designed to serve his particular purposes.

A KEY FOR THE PHOTO-IDENTIFICATION OFGLACIAL LANDFORMS

William E. Powers (Northwestern University)

A SUMMARY is presented herein of a key for the photo-identification ofglacial landforms developed by the writer and Dr. Clyde F. Kohn as part of

Research Project N -7-onr-45-005, under a contract between the Office of NavalResearch and Northwestern University. Field work was completed during thesummer of 1950.

The objective of this part of the project was to produce a key or study pro­cedure by which a photo-interpreter untrained in glaciation or geomorphologycan identify correctly the landscape features in a region formerly occupied bycontinental glaciers. Such' glaciated regions form a large part of the northernUnited States and Canada, portions of Alaska, and areas of unknown, but almostcertainly vast extent, in northern and northeastern Asia. The photo-interpreteris expected to have vertical stereopairs of aerial photographs, and should alsomake use of all available information on the climate, vegetation, geology, andhuman occupancy of the region considered. For field studies, five areas wereselected in the glaciated region adjacent to Lake Michigan, and their landformswere studied and mapped in detail. In addition, ground photographs of alllandform types .studied were taken in stereopairs, so as to show the photo­interpreter the ground appearance of the features which he identifies on aerialphotos.

FORM OF KEY

Analysis of the landforms in the five areas selected disclosed eleven typesof direct glacial origin and four types of non-glacial origin but likely to be as­sociated with or adjacent to the glacial types. A form of key was adopted inwhich, by a series of questions pertaining to specific features apparent on verticalstereopairs of photos, the photo-interpreter is able to separate the landform typesinto smaller and smaller groups until only two remain; a final question thenidentifies the form. The first question selected is whether the fOfm is of glacialor non-glacial origin; it was considered necessary to examine not one butseveral contrasting characteristics to make this decision. Subsequent questionsdeal, for simplicity, with only one element in the appearance of the feature to beidentified.

A KEY FOR PHOTO-IDENTIFICATION OF GLACIAL LANDFORMS 777

9. Till knobs other than drumlins10. Kames11. Eskers12. Valley train terraces13. Kame terraces14. Outwash plains15. Filled basins

CLASSIFICATION OF LANDFORMS

Fifteen types of landforms were recognized in this study. Of these, types 1to 4 are non-glacial but may be closely associated with glacial types, whiletypes 5 to 15 are directly glacial in origin:

1. Lacustrine Plains2. Valley plains of streams3. Stream-dissected plains or hill lands4. Dunes5. Glaciated bedrock-controlled plains6. Rough and moraine7. Undulating till plain8. Drumlins

Non-GlaciatedGenerally found in non-glaciatedregion.Few or no lakes and swamps;drainage may be good. Exception:flat lacustrine plains or valley plainmay be swampy and poorlydrained.Branching or rectangular; inte­grated and complete pattern; orregularly meandering. (Appliesonly if stream pattern is present.)Estensive areas of similar land­forms.Some but not all landforms may berelated directly to stream erosionpattern, if present.Irregular but connected ridgeswith angular or branching patternmay be present.Low ridges tend to be straight withuniform crests. (Dunes are crescen­tic in plan.)Closed deep basins rare save indunes.Oriented forms rare save beachridges, sand bars, or crescenticdunes.Crescentic ground plan common indunes.Hilly belts if present are not higherthan surrounding country, savedunes.Darker soils commonly organizedinto branching or fish bone pat­terns. Flat lake plains may haveirregular soil patterns. Dunes mayhave crescentic patterns of lightsoils.

(a) Many small diverselandforms.

(b) Many landforms appearunrelated to any streampattern.

(c) Rounded, isolated hillsand ridges are common.

(d) Low, narrow ridgeswinding with crests of'varying altitude.

(e) Closed deep basins com­mon.

(£) Oriented or parallelforms may be present.

(g) Forms of crescenticground plan very rare.

(h) Hilly belts higher thansurrounding countrymay be present.

pat- (a) Irregular, unorganizedpattern of dark soils onlow ground. Soil patternunrelated to stream pat­tern.

d. Landformtypes andpatterns:

c. Stream pat- (a) Aimless; incomplete pat-tern (if pre- tern.sent) :

e. Soilterns:

INTERROGATION PROCEDURE

The following fourteen questions form a guide for differentiating and identi­fying the 15 landform types:

IS LANDFORM TYPE GLACIATED OR NON-GLACIATED?

Glaciated1. a. Location: (a) In region believed to

have been glaciated.b. Drainage: (a) Many lakes and swamps;

. poor drainage.

778 PHOTOGRAMMETRIC ENGINEERING

NON-GLACIATED FORMS

II. Is area mainly flat plain, or is it hilly or deeply cut by valleys?a. Lacustrine plains (1) and valley plains of streams (2) are mainly flat.b. Dissected plains or hill lands (3) and dune areas (4) are dominantly hilly.

III. If area is mainly flat plain, is it extensive and non-linear, or is it narrow and linear?a. If area is extensive, non-linear, and unoriented with respect to a stream, it is

lacustrine plain (1).b. If area is linear with bounding bluffs and is related to a present or former

stream, it is a valley plain (2).IV. If area is hilly or deeply cut by valleys, does it contain connected ridges integrated to a

drainage pattern, or small individual hills with depressions but with few streams?a. If area has an integrated, orderly drainage pattern separating organized, inte­

grated dividing ridges of branching or rectangular pattern, the area is dissectedplain or hill land (3). .

b. If there are many small hills, some of crescentic pattern, associated with de­pressions but having few streams and no'organized drainage pattern, area isdunes (4).

GLACIATED FORMS

V. Is area one of thick glacial drift, or is drift thin w,ith topography dominated by bed­rock?a. Angular cliffs, very steep or vertical slopes, bare rock outcrops with few or no

plants, and stone quarries indicate bedrock-controlled plain (5).b. The absence of angular ciiffs, of very steep or vertical slopes unless associated

with undercutting by a stream or wave action, of bare rock exposures withoutplants, and of stone quarries-indicates that landforms are of glacial drift de-posited by glacier (6 to 15). •

VI. Are all landform summits rounded or rolling, or are there flat-topped forms of ac­cordant level?a. Rounded glacial landforms include rough end moraine (6), undulating till

plain (7), drumlins (8), other till knobs (9), kames (10), and eskers (11).b. Flat-topped glacial landforms include valley trains (12), kame terraces (13),

outwash plains (14), and filled basins (15).

If forms are rounded:

VII. Is area extensive including many elevations and depressions, or does area consist of anindividual hill br ridge?a. Rough end moraine (6), and undulating till plains (7) are extensive.b. Drumlins (8), other till knobs (9), kames (10), and eskers (11), are individual

hills or ridges.VIII. If area is extensive, do the rounded elevations form a belt of hilly topography with

moderate to strong relief. or is distribution pattern non-linear and relief low?a. Hilly belts of strong to moderate relief are end or terminal moraine (6).b. Low relief and lack of arrangement among the swells and basins indicate

undulating till plain (7).

If landform is individual hill or ridge:

IX. Are the sides steeply or gently sloping?a. Drumlins (8) and othe'r till knobs (9) have gently sloping sides.b. Kames (10) and eskers (11) have relatively steeply sloping sides.

X. If side slopes are gentle, does form have oval, oriented ground plan with one endsteeper than other, or is plan non-oval with no spefial relation of side slopes to groundplan?a. Oval, oriented till hills with one end steeper than other are drumlins (8).b. Non-oval hills with slope angle unrelated to form are till knobs (9).

A KEY FOR PHOTO-IDENTIFICATION OF GLACIAL LANDFORMS 779

XI. If slopes are steep, is the landform a sharp, roughly circular hill or is it an enlongatedridge?a. Sharp, steep, roughly circular hills are kames (10).b. Elongate, steep-sided ridges are eskers (11).

If glacial landforms are flat or contain flat-topped forms:

XII. In its broad aspects, is the form terrace-like, with higher ground on one side and loweron the other, or is it a non-terrace?a. Valley trains (12) and, kame terraces (13) are terrace-like.b. Outwash plains (14) and filled basins (15) are non-terrace forms.

XIII. If terrace-like, does the outer edge of the terrace form show irregular knobs and pitsdue to ice-contact when form was being deposited, or does outer edge appear smoothor scalloped as if eroded by a stream? , 'a. Valley train terraces (12) have smooth, stream-eroded edges or margins.b. Kame terraces (13) have irregular, ice-contact margins. (Where such ice-contact

margins have been eroded to smooth slopes, the kame terrace looks like a valleytrain terrace.)

XIV. If flat form is not a terrace, is it a poorly-drained basin-like form with a very flatfloor, or is it dominantly a well-drained plain?

a. A well-drained plain with or without pits or channels is an outwash plain (14).b. A poorly-drained flat-floored basin is a filled basin (15).

Typical examples of each of these 15 landform types are shown in verticalstereogiams and also in stereopairs of ground photographs. After each form isidentified, the photo-interpreter is directed to verify his identification by com­paring its observed characteristics with a list of all possible characteristics thatsuch a feature may possess. Agreemen~ in several respects, and few or no con­tradictions, are considered to constitute verification.

It is believed that this identification procedure, if faithfully' followed, willquickly train the photo-interpreter to recognize landform types due to or asso­ciated with glaciation. Experience will speed the identification process, and willindicate associations of landform types that permit rapid generalizations andthe quick recognition of individual forms. A procedure of this type is particularlywell adapted to the study of areas where all or most features are due to a singleprocess (here glaciation) and hence all elements of the landscape may be con-sidered to be related in origin. '

ABC's OF PHOTOGRAMMETRYPART I PART II'

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ABC's OF PHOTOGRAMMETRY ~:s~~n5g~on 13, D.C.