PHOTO INTERPRETATION IN PROSPECTING 
FOR GRANULAR CONSTRUCTION MATERIALS 
by J. D. Mollard 
J. D. Mollard and Associates Limited, Regina, Canada 
Abstract 267 photo interpretation studies made in search of naturally occuring construction 
materials, were summarized. Most of these studies concerned the discovery of sand and gravel 
sources. Drawing on this source of information, the author outlines objectives of these studies, 
relates office airphoto to follow-up field studies, and discusses the techniques of photo analysis 
and interpretation used. Methods of presenting data on maps and rating of prospective deposits 
for a particular requirement are given. Success and limitations are dealt with. 
Résumé Dans cette note, on a condensé 267 diverses études d’interprétations photogra 
phiques destinées à la recherche de matériaux de construction. La plupart de ces recherches 
concernent des sables et des graviers. En se referrant à ces sources d’informations, l’auteur en 
décrit les objectifs, quel en fut le déroulement, et il discute des techniques d’interprétation et 
d’analyse photographique employées. Il est fait mention des méthodes de présentation des 
données sur les cartes et de la classification des divers dépôts prospectés selon des exigences 
particulières. Il est fait mention des succès et des restrictions de ces recherches. 
Zusammenfassung 267 Einzelne Studien auf Grund der Luftbild-Interpretation in der 
Suche nach natürlichen Lagerstätten von Baumaterial lieferten das Material für diesen 
Vortrag. Bei den meisten Studien handelte es sich um Sand- und Schotter-Ablagerungen. 
Auf Grundlage dieser Auskunftsquellen skizziert der Verfasser den Zweck dieser Studien, 
beschreibt die der Gelände-Arbeit folgende Luftbild-Auswertung und bespricht die Technik 
der Photo-Analyse und der Interpretation. Darstellungs-Methoden der Daten auf Karten und 
die Beurteilung der zu erwartenden Lagerstätten für bestimmte Verwendungszwecke werden 
ebenfalls besprochen. Erfolge und Beschränkungen werden eingehend besprochen. 
Introduction 
Data summarized in preparing this paper are drawn from 267 consulting 
assignments involving discovery and mapping of sand and gravel deposits by 
photo interpretation methods. Altogether, an area of approximately 151,000 
square miles was searched in aerial photographs. Slightly over 12,000 prospec 
tive granular sources were mapped for follow-up field checking. Many of the 
12,000-odd sand and gravel deposits were inspected in the field by the photo 
interpreter carrying out the search. However, a notably high proportion of the 
prospects mapped were field checked by client’s engineers or materials tech 
nicians using various types of subsurface-exploratory equipment. 
Nearly all granular prospects mapped from the photos are glaciofluvial in 
origin. A small percentage were recent alluvial deposits. Deposits mapped range 
in quality from small shallow dirty sands to extensive deep clean coarse gravels 
and sands. While these deposits vary widely in areal extent as well as in depth, 
based on the results of random-sample studies, it is safe to say that over 95 
percent of all deposits mapped are less than 100 acres in area and less than 20 
feet in average depth. Sand and gravel deposits identified from airphotos range