FEATURE
IDENTIFICATION
Shape
Cultural Features
- some features such as airport runways have a distinctive shape
which make them easy to identify
- roads are usually regular in shape which tends to make them easy
to identify
- railways are also of uniform width and have long, straight stretches
and more gentle curves than roads
- bridges should be looked for wherever roads or railways cross a
body of water; they are generally of uniform width, and will often
cast a shadow which reveals their structure
- buildings have a variety of regular shapes that vary considerably
in size depending upon the use of the structure
Natural Features
- generally have more irregular shapes
- quite easy to tell the difference, for example, between an orchard
(rows of trees with regular spacing) and a forest area with irregular
tree growth
|
|
Pattern
- formed by the repetition of a feature
eg farm fields, rows of trees in an orchard, oil storage tanks at a refinery
|
Shadow
- high objects such as towers, chimneys, bridges, or high buildings
cast shadows which help you to identify the object
- shadows can help one to tell the time of day that the photo was taken
|
| Tone Cultural Features
- roads and tracks will usually have a light grey tone as they are
fairly reflective of light
- railways: medium grey
- bridges: vary according to construction material
Natural Features
Water
- generally appears dark grey or black since it absorbs much of the
light
- if the water body is fairly shallow with a light-coloured or weedy
bottom, or if it carries a high silt load, it will reflect more light
and appear lighter in colour
- rough water has many reflective surfaces so it may range from dark
to almost white
Vegetation
- most will vary from shades of grey to black
- since deciduous, broad-leafed trees reflect more light than coniferous
trees, they appear in lighter shades
Soil
- bare ground usually has a light colour but the wetter it is, the
darker the tone
Crops
- cultivated fields and fallow fields are almost white in tone
- well-developed crops will be dark grey but tones vary according
to the season, type of crop, and stage of growth
General Guide
Spring: sharp, distinct field patterns due to differences in tillage
and crop development
Summer: dark tones for maturing crops and heavily leafed trees
Fall: distinct field patterns because of the various stages of crop
development and harvesting
Winter: when there is little or no snow cover, tones are generally
drab and dull
|
INTERPRETATION
Location
- refer to a topographic map
to locate the area shown in the air photo. Often compass directions
are not given on an air photo; therefore if you are required to find
a particular direction on an air photo, you will need to utilize an
accompanying topographic map.
Scale
- see next lesson
Physical Features
Broad Patterns
- look at the whole photograph to get a general picture of the area
Drainage
- describe the distribution of lakes, rivers, and streams, and general
drainage conditions
Natural Vegetation
- determine the approximate percentage of the area which is covered
by natural vegetation
Soils
- if field patterns are obvious, a determination of the crops grown
could indicate particular
soil types
Climate
- use information about drainage, vegetation, and soils to makes
inferences about the climate
(see “Topographic Map Interpretation” notes)
|
| Cultural Features
Settlements
- how many settlements are there?
- where are they located?
- how are they distributed (i.e. clustered, scattered, regularly
or irregularly spaced)
|
| Transportation and Communication
Roads
- what variety of roads are found (i.e. dual highways, single highways, paved,
gravel, etc.)?
- are the routes direct or twisting?
Airport
- where is it located in relation to any visible settlements?
- how long are the runways?
Other
- are there hydroelectric transmission lines, telegraph or telephone lines?
- are any communication towers visible?
- how do these features relate to physical and cultural patterns? |
| Economic Activities
- note any evidence of fishing, forestry, mining or quarrying, manufacturing,
recreation or tourism, or agriculture and its distribution
- establish any relationships between economic activity and the physical
and cultural features of the area
|
button on the Action menu to proceed.