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Table of Contents
Foreword
Preface
Glossary

Chapter 1: Introduction

1.4: Tonal Variations in the Landscape East of Elphinstone

In this area of hummocky ground moraine topography, numerous small lakes (sloughs) can be seen. In the centre and north they are dark-toned 1 whereas in the southeast they are light-toned 2. The light tone is a result of the relationship between the camera angle, the sun angle, and the water surface, a phenomenon known as specular reflection. The diagram below shows the conditions under which specular reflection occurs. Objects at E would show the effect whereas objects at F would not.

The very light-toned lake in the west 3 is probably a dried up lake with a salt surface resulting from evaporation. The same process seems to be starting at another lake further south 4, which was obviously once much larger 5 and now has white deposits along its shore 6.

The photo also illustrates the interpretation criterion “texture.” The central lake 7 is uniformly dark-toned and has a smooth texture whereas wooded areas to the north 8 and south 9 have variable tones resulting from the way light falls on tree crowns and sides. The result is a mottled texture.

Figure 1.4: Tonal Variations in the Landscape East of Elphinstone

Figure 1.4: Tonal Variations in the Landscape East of Elphinstone

 

Figure 1.4

Vertical air photo: A11569-201

Flight height: 7,920 feet a.s.l.; lens focal length: 152.4 mm

Scale: 1:14,700 (approx.)

Date: August 18, 1948

Location: Township 18, Range 21 WI

Map sheets: 1:250,000: 62K Riding Mountain

1:50,000: 62 K/9 Elphinstone