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Chapter 1: Introduction

1.15: The Influence of Scale Illustrated by Photos of Part of the Assiniboine River Southwest of Lavenham

a) Smallest scale:

This high level, small-scale photo shows a large stretch of the eastward flowing Assiniboine River 1 and the junction with Cypress River 2. Specular reflection results in both rivers having a very light tone near their junction 3. In this area the Assiniboine River is incised into the Assiniboine Delta. Dunes 4, now mainly stabilized by grasses 5 and trees 6, have been created by wind action.

The area covered measures 11.375 miles (18.3 km) by 11.375 miles (18.3 km) for a total area of 129.4 square miles (335.1 square km). The sections of the DLS system (one square mile in area) 7 are a good rough indicator of the area covered. PTH 34 8 crosses the area from north to south.

b) Larger scale:

This larger scale photo covers only a small part of the area shown on figure 1.15a. The side of the photo measures 5 miles (8 km) for an area of 25 square miles (64 square km). However, more detail can be observed than on 1.15a; for example, sand bars 1 can be seen along the course of the Assiniboine River 2. But perhaps the clearest example is the possibility of locating individual trees 3, some of which can be identified as coniferous trees 4 on the basis of their shadow shapes. Note also south of the Assiniboine, east of PTH 34 5 an area of deciduous woodland has tonal variations 6 which produce a mottled texture, whereas the same area at the smaller scale of figure 1.15a has a uniform tone that produces a smooth texture.

c) Largest scale:

The increase in scale results in an even smaller area covered; the photo side is 2.27 miles (3.7 km) with an area of 5.15 square miles (13.34 square km). This results in much more detail being detectable, particularly when compared with figure 1.15a (smallest scale). Details seen along the Assiniboine River 1 are sand bars 2 and the exact location of the mouth of the Cypress River 3. Meander scrolls 4 indicate previous river positions. Tonal variations in the woodland produce a mottled texture 5, and deciduous trees with rounded shadows 6 can easily be distinguished from coniferous trees with triangular shadows 7. Details of a gravel pit 8 east of PTH 34 9 can be obtained whereas the pit is only just identifiable in figure 1.15a. One final detail observable is supports for the bridge across the Assiniboine, five of them in all 10.

Figure 1.15.a: smallest scale

Figure 1.15.a: smallest scale

Figure 1.15a

Vertical air photo: A21666-116

Flight height: 22,420 feet a.s.l.; lens focal length: 3.5 inches

Scale: 1:79,200 (approx.)

Date: July 21, 1970

Location: Townships 8 and 9, Ranges 10, 11, and 12 WI

Map sheets: 1:250,000 62G Brandon

1:50,000 62G/10 Treherne

Figure 1.15.b: larger scale

Figure 1.15.b: larger scale

Figure 1.15b

Vertical air photo A15577-24

Flight height: 20,000 feet a.s.l.; lens focal length: 6 inches

Scale: 1:35,800 (approx.)

Date: October 11, 1951

Location: Township 8 and 9, Range 11 WI

Map sheets: As for 1.15a

Figure 1.15.c: largest scale

Figure 1.15.c: largest scale

Figure 1.15c

Vertical air photo: A16574-86

Flight height: 9,000 feet a.s.l.; lens focal length: 6 inches

Scale: 1:16,050 (approx.)

Date: June 19, 1959

Location: Township 8, Range 11 WI

Map sheets: as for 15.1a