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Transactions of the Symposium on Photo Interpretation

The physiographic types are:
1. Bedrock-Controlled Relief
subdivided into : a. Rock plains b. Low hills c. Bold Hills d. Hills
showing crag and tail, or roches moutonnées.
2. Drift-Controlled Relief
subdivided into : a. Undifferentiated drift b. Drumlinized and fluted
drift plains c. Drumlin bog d. Sand and gravel including Eskers.
Deep gorges are also indicated.
In the first group of reconnaissance techniques the classification is such that
it allows direct plotting from photo observation to available base map. In Ca
nada the largest scale total coverage base map is at a scale of 1 : 500,000
(approximately 8 miles : 1 inch). This implies reduction of data from the
1 : 40,000 vertical or oblique photographs to an area approximately the size of
the average postage stamp, by eye or pantograph. The plotting is aided by a
template which is placed over the map showing only the area covered by the
photograph. Subsequent reduction of the map to 1 : 1,000,000 can be made
with some generalization but no change in classification. This technique has
been used with great success in the whole of Labrador-Ungava [5, 11, 17],
N. E. Kewatin [1, 3, 4, 34], Southampton Island [2, 10, 34], Baffin Island [34],
parts of northern Ontaria [46], and underlies the whole of the recent “Glacial
Map of Canada” [15]. These areas imply at least two million square miles of
photo interpretation.
The second method involved the recognition of small scale boundaries on
relatively large scale photographs. This has been facilitated by use of reduced
scale mosaics. The classification is chosen so that the general recognition of the
types can be done on the mosaic with only selective stereoscopic examination.
Data from the mosaics, which are frequently at a scale of 1 mile : 1 inch, can
be further reduced with no change in classification. An idea of the use of this
technique can be gained from a study carried out in Newfoundland [51]. The
whole island (20,000 square miles) was mapped on a classification based on
surficial geology which graded agricultural suitability. The whole survey was
completed by two men in six months, the resulting accuracy of agricultural
suitability being over 80%.
Small scale survey techniques can be said to apply where the base map
coverage and photo-scale allow classifications to be more sub-divided and pre
cise than the reconnaissance survey. The resulting maps can be used as a basis
for sub-regional analysis [19, 20, 48, 54] and perhaps even systematic studies
[54], as well as to present the broad regional patterns.
Typical of the classifications is one being used for geomorphology of the
prairie provinces [54]. It contains 51 subdivisions, differentiating between such
forms as moraines, former crevasse fillings, active and fossil sand dunes, misfit
and normal streams, among others. Identification is by steresocopic examina-