How to interpret aerial photographs

Photo interpretation is the art of identifying visible details from their images on a photographic print. The best aid to this is the stereoscope. However it is easy to become skilled in this work by examining single photographs.

A reading glass will help a great deal. Skill will come by examining all types of photographs and comparing them with maps or, best of all, with the ground itself. Start with prints with a scale of 1:20 000 or larger.

Interpretation requires the study of three things: i) tone, 2) light and shadow, 3) shape and size.

Tone . A large amount of light reflected from an object results in a white object on the print, and no light results in a black object. In between these two extremes are all the shadows of gray.

This shade of gray of an object is known as the tone of the image. The less light reflected the darker will be the shade of gray, or the darker the tone,

Light and shadow. When studying the photographs always remember about the source of light and have the shadows on the print fall toward you.

This puts the light in the same position the sun was in when the picture was taken.

This is very important when studying relief.

Shadows often give the shape and size of an object that appears on a photograph. The top of a square building would look the same if it were one-story or ten-story building; but the shadow would be much different.

Shape and size. Man-made features are usually bounded by straight or curved lines, while natural features usually have irregular edges. It is important to keep the scale in mind when studying the shapes and sizes. A light square image may represent a building on a 1 : 4,800 print. But the same size of square may represent a cultivated field in a 1 : 20,000 print.

A s s i g n m e n t s

1. Comprehension questions:

1.With what print shall we start photo interpretation? 2. What does photo interpretation consist of? 3. When is the tone of the image darker? 4. What is important for studying relief? 5.What is characteristic for natural features on photoes?

2.Describe applications of a reading glass.

3. Give a short summary of the text.

Lesson 5

Text A. Figure and size of the earth

1.Read and memorize the following words:

above - над

accuracy - точність

approximation- наближення

base (v) -- базувати

below - під

circle (n) - коло

closely - тісно

consider – розглядати

correspond – відповідати

cut (v) – перерізати

define - визначати

degree - градус

depth - глибина

difference -різниця

distribution -- розподіл

elevation - підвищення, висота

figure - фігура

improve -. покращати

intersect - перетинати

measure (v) - вимірювати

need (v) - потребувати

normal - перпендикулярний

pass (v) - проходити

plane (n) - площина

point - точка, крапка

relate - бути зв'язаним, мати відношення

represent - представляти

size - розмір

sphere - сфера

state (v) - констатувати, формулювати

subject (a) - що підлягає

suitable - придатний

various - різний

11. Expressions for the text comprehension:

accurate observations - точні спостереження

angular coordinates - кутові координати

angular distance - кутова відстань

axis of rotation - вісь обертання

ellipse of rotation - еліпс обертання, еліпсоїд

empirical equation - емпіричне рівняння

in practice - на практиці

land masses - маси суші, землі

linear distance - лінійна відстань

linear unit - лінійна одиниця

mean sea level - середній рівень моря, умовний горизонт

meridian plane - площина меридіану

oblate spheroid- сплющений сфероїд

parallels of latitude - паралелі широти

plumb line - висок

reference level - рівнева поверхня, контрольний рівень

royal observatory - королівська обсерваторія

system of coordinates - система координат

that is - тобто

unit difference - питома різниця

vertical distance — вертикальна відстань

Grammar Focus

*Any plane parallel to the Equator cuts the surface of the spheroid in a circle, all points on this circle having the same latitude.

Незалежний (абсолютний) дієприкметниковий зворот (The Absolute Participle C0nstruction)

Складається з іменника в загальному відмінку або займенника в називному відмінку та дієприкметника. Може стояти перед головним реченням або після нього та відокремлюється комою. Перекладається підрядними реченнями часу, умови, причини, супутніх обставин із сполучниками після того як; коли; так, як; оскільки; якщо та іншими в першому випадку або самостійним реченням із сполучниками причому;а; i в другому.

The weather permitting, we shall go to the park. – Якщо погода дозволить, ми підемо в парк.

The treaty is done in the Russian and Chinese languages, both texts being equally valid. - Угода складена на російській та китайській мовах, причому обидва тексти мають однакову силу.

Any plane parallel to the Equator cuts the surface of the spheroid in a circle, all points on this circle having the same latitude. – Будь-яка площина, паралельна екватору, перерізає сфероїд колом, причому всі точки при цьому мають однакову широту.

Figure and size of the earth

As a first approximation the earth may be considered as a sphere, but according to accurate observations, its figure is more closely represented by an ellipse of rotation - that is, an oblate spheroid, the shorter axis being the axis of rotation. The figure of the earth has been defined by various empirical.equations, the constants of which being based on observations and being subject to modification as the number of observations increases and their accuracy is improved. The geometrical figures defined by these equations cannot exactly represent the shape of the earth because of the a symmetrical distribution of the water and land masses.

To define the position of a point on the earth's surface a system of coordinates is needed, and as such the terms latitude, longitude and elevation or depth are used. The first two are expressed by angular coordinates and the third is expressed by the vertical distance, stated in suitable linear units, above or below a reference level that is closely related to mean sea level. The latitude of any point is the angle between the local plumb line and the equatorial plane. Because the earth can be considered as having the form of a spheroid, and as the plumb line, for all practical purposes, is perpendicular to the surface of the spheroid, any plane parallel to the equator cuts the surface of the spheroid in a circle, . all points on this circle having the same latitude. These circles are called parallels of latitude. The latitude is measured in degrees, minutes, and seconds north and south of the equator, the linear distance corresponding to a difference of one degree of latitude would be the same everywhere upon the surface of a sphere, but on the surface of the earth the distance represented by a unit of latitude increases by about 1 per cent between the equator and the poles.

The line in which the earth's surface is intersected by a plane normal to the equatorial plane and passing through the axis of rotation is known as a meridian. The angle between two meridian planes through two points A and B on the surface of the earth is the difference in longitude of the two points. In practice, the longitude is the angular distance measured in degrees, minutes, and seconds east or west from a standard meridian plane, generally that of the royal observatory at Greenwich, England. Thus, the longitude is measured from 0° to 180° east and west of Greenwich. On the surface of the earth the linear distance equivalent to unit difference in longitude is nearly proportional to the cosine of the latitude.

The distance between points on the earth's surface and the area represented by a given zone cannot be correctly represented unless the size of the earth is known.

E x e r c i s e s

I. Give Ukrainian equivalents of the following international words from the text:

figure, sphere, ellipse, rotation, empirical, constant (n), modification, geometrical, asymmetrical, mass, position, system, coordinate, vertical, distance, local, line, equatorial, form (n), spheroid, practical, perpendicular, parallel, equator, minute, second(n), per cent, pole, meridian, observatory, equivalent, cosine, zone

II. Find in the text adjective + noun, noun + noun word combinations and translate

III. Give the opposites of::horizontal, short, above, various, north, east, high, wide, inner.

IV.Translate the following sentences payng attention to the absolute participle constructions:

1.The earth may be considered an oblate spheroid, the shorter axis being the axis of rotation. 2. Any plane parallel to the equator cuts the surface of the earth in a circle, all points on this circle having the same latitude. 3. The figure of the earth has been defined by various empirical equations, the constants of which being based on observations. 4. The number of observations increasing, the accuracy of the map is improved. 5. The latitude and the longitude being known, the island could be marked on the map.

V. Analyse the S-P-O structure of the sentence:

The geometrical figures defined by these equations cannot exactly represent the shape of the earth because of the asymmetrical distribution of the water and land masses.

VI.Define the functions of the participle constructions and translate the following sentences:

1.The linear distance corresponding to a diference of one degree of latitude would be the same everywhere upon the surface of a sphere.2. The work of our surveying party was interrupted because a radiogram was received informing us about a heavy storm approaching the region of our exploration. 3. Having corrected the triangles, we began calculations, 4. When plotting from the astronomic positions, distant hills are a great help in a survey.

VII. Comprehension questions:

1.How may the figure of the earth be represented? 2. Is the accuracy of observations improved? 3. What is needed to define the position of a point on the earth's surface? 4. When are angular coordinates used? 5. What is the latitude? 6.What are parallels of latitude? 7. How is the latitude measured? 8. What is a meridian? 9. What is the longitude? 10. Where is a standard meridian plane?

VIII. Give a one-sentence definition of e l e v a t i o n.

IX. Annotate the third paragraph.

X. Speak about:

a) a figure of the earth, b) latitude, c) longitude.

Text B. The globe grid

1.Read aloud amd memorize the following words:

agree upon - домовитись

cartographer - картограф

contain - вміщувати

converge - сходитись

decrease(v) - зменшувати/сь/

depict -зображати

distort - спотворювати, викривляти

draw - малювати

geographer - географ

look for - шукати

near (v) - наближатись

projection - проекція

property - властивість

retain - зберігати, пам'ятати

right (a) - прямий

II. Expressions for the text comprehension:

equal length - рівна довжина

extent of variance - ступінь варіаціїglobe grid - світова мережа, (сітка)

grid relationships - відношення мережи

grid system - система сіток

key reference point - ключова точка відліку

line of reference - лінія початку відліку

map grid – сітка карти

map maker - виготовлювач карт, картограф

map user - споживач карт

north-south line - лінія північ- південь

primary tool - головний інструмент

prime meridian- головний, початковий, основний меридіан

right angle - прямий кут

spatial analysis - аналіз простору

spherical earth - земля у формі сфери, сфероїд