Cartography, Projections and Scales

Summary

This video explores essential concepts in cartography, including projections and scales crucial for interpreting navigation charts. It defines cartography, differentiates maps and charts, and delves into various projection types like azimuthal, cylindrical, and conical, explaining their characteristics and uses. The video also covers how projections affect map accuracy and introduces the concept of scale, illustrating how to calculate real distances from map measurements. These insights are valuable for understanding navigation and mapmaking.

Takeaways

• 🌍 Cartography is the science of representing the Earth's surface on a 2D surface like paper at a smaller scale.
• 🗺️ A chart is a specialized type of map designed for a specific purpose, such as navigation for ships or planes.
• 🔍 The challenge of cartography lies in accurately representing a 3D figure like the Earth on a 2D surface without distortion.
• 📐 Projections are methods of representing the Earth's surface on a 2D plane, with various types preserving different properties like shape, area, distance, or direction.
• 📈 There is no single projection that can perfectly preserve all characteristics, so choices are made based on the map's purpose.
• 💡 The concept of projection can be visualized by imagining a light bulb inside the Earth projecting its surface onto a surrounding piece of paper.
• 🌐 Azimuthal projections have no distortion at the center point and are used to map the poles but are not common for navigation.
• 📏 Cylindrical projections show no distortion along the equator, with increasing distortion away from it, and are useful for direction measurement.
• 📐 Conical projections touch the Earth at two standard parallels, preserving accuracy at these points with distortion increasing away from them.
• 🔢 Scale is the relationship between a map measurement and the actual Earth measurement, essential for maintaining correct proportions.
• 📏 Maps publish their scale in various formats, which can be used to calculate real-world distances without tools like a plotter.

Q & A

What is cartography and where does the word come from?

Cartography is the science of representing a part or all of the Earth's surface graphically at a smaller scale on a 2D surface such as a piece of paper. The word comes from 'cardo,' meaning map, and 'graph,' meaning to write.

What is the difference between a map and a chart?

A chart is a specialized type of map that contains information related to a specific purpose, such as nautical charts for sea navigation or aeronautical charts for air navigation.

Why is it difficult to represent the Earth's surface on a 2D plane?

It is difficult because representing a 3D figure like the Earth on a 2D plane cannot maintain all its proportions, scales, and features accurately. This requires the use of projections that introduce some level of distortion.

What are map projections and why are they important?

Map projections are methods used to represent the Earth's curved surface on a 2D plane. They are important because they allow us to create maps, but each projection introduces some distortion in shape, area, distance, or direction.

What is a conformal projection and what does it preserve?

A conformal projection maintains the correct shape of objects and surfaces, ensuring that angles and shapes are preserved accurately.

What does an equivalent projection maintain?

An equivalent projection maintains the magnitude of the area of objects and surfaces correctly, ensuring that the size of areas is accurate.

What is an azimuthal projection and where is it most accurate?

An azimuthal projection is a type of map projection where a flat piece of paper touches the Earth at a single point, typically a pole. It is most accurate at the center point where the paper touches the Earth, with distortion increasing as you move away from this point.

What are the characteristics of a cylindrical projection?

In a cylindrical projection, the map is created by projecting the Earth's surface onto a cylinder. It is most accurate around the equator, with distortion increasing towards the poles. Meridians and parallels intersect at right angles, making it easier to measure direction, but the size of areas can be distorted.

How does a conical projection differ from a cylindrical projection?

A conical projection involves projecting the Earth's surface onto a cone that touches the Earth along two standard parallels. It preserves accuracy and properties near these parallels, with distortion increasing away from them. Unlike cylindrical projections, it offers a different pattern of distortion suitable for mid-latitude regions.

What is the formula for determining real distance on a map using scale?

The formula for determining real distance is: Real Distance = Map Distance x Scale. For example, if the map scale is 1:1,000,000 and the map distance is 16 centimeters, the real distance is 16,000,000 centimeters, which can then be converted to other units like nautical miles.

Outlines

00:00

🗺️ Cartography, Projections, and Scales Overview

This paragraph introduces the fundamental concepts of cartography, which is the science of graphically representing the Earth's surface on a 2D surface like paper at a smaller scale. It explains the difference between a map and a chart, with the latter being a specialized map for specific purposes such as navigation. The paragraph discusses the challenges of accurately representing a 3D Earth on a 2D surface and introduces the concept of map projections, which are methods to project the Earth's surface onto developable shapes like cylinders or cones. It also explains the types of projections based on the properties they preserve, such as conformal, equivalent, equidistant, and azimuthal projections, and acknowledges that no single projection can maintain all properties perfectly.

05:01

🌐 Understanding Map Projections and Their Distortions

This paragraph delves deeper into the specifics of different map projections, including azimuthal, cylindrical, and conical projections. It describes how each projection touches the Earth at specific points, resulting in varying degrees of accuracy and distortion. The azimuthal projection is highlighted for its accuracy at the center point and increasing distortion away from it. The cylindrical projection is noted for its accurate representation near the equator and distortion as one moves away from it, exemplified by the incorrect size comparison between Africa and Greenland. The conical projection is explained as having accurate representations at standard parallels with distortion increasing away from these points. The paragraph also touches on the arrangement of projections to map areas accurately and mentions commonly used projections for navigation, such as the Lambert Conformal Conical and the Mercator Conformal Cylindrical.

📏 The Importance of Scale in Aeronautical Charting

The final paragraph focuses on the concept of scale in aeronautical charting, which is crucial for maintaining correct proportions of terrain and objects. The scale is defined as the ratio of real distance to map distance, and its importance is emphasized for determining distances without a plotter. The paragraph provides examples of how scales are published on maps and demonstrates how to calculate real distances using the scale formula with two different examples. It also explains the unit conversion from centimeters to nautical miles. The summary concludes with the practical use of a plotter for measuring distances and the educational value of understanding scales in navigation.

Keywords

💡Cartography

Cartography is the science of creating maps, which involves representing a part or all of the earth's surface on a two-dimensional surface like paper at a reduced scale. In the video, cartography is the overarching theme, as it discusses the various aspects and challenges of map-making, including the use of projections and scales to accurately depict the earth's features.

💡Projections

Projections refer to the methods used to represent the three-dimensional surface of the earth on a two-dimensional plane. The script explains that no single projection can perfectly maintain all aspects of the earth's proportions and features, hence different types of projections are developed to preserve different properties such as shape, area, distance, or direction. Examples given in the video include conformal, equivalent, equidistant, and azimuthal projections.

💡Scale

Scale is the ratio between a distance on a map and the corresponding distance on the earth's surface. It is crucial for maintaining the correct proportions of terrain and objects on a map. The video script explains that all maps are published with a scale, which can be numerical, graphic, or in plain text, and provides examples of how to calculate real-world distances using the scale.

💡Map

A map is a graphical representation of an area, which can be a part or the entirety of the earth's surface. The script distinguishes between a general map and a chart, with the latter being a specialized type of map designed for specific purposes, such as navigation.

💡Chart

A chart, as mentioned in the script, is a specialized map that contains information relevant to a particular purpose, such as nautical or aeronautical charts for maritime and air navigation, respectively. Charts include specific details like sea depth, lighthouses, ports, obstacles, navaids, airports, and air spaces.

💡Conformality

Conformality in the context of map projections refers to the preservation of the correct shape of objects and surfaces. A conformal projection, such as the Lambert Conformal Conic, is used when maintaining the shape is more important than other properties, as illustrated in the script.

💡Equivalent Projection

An equivalent projection is one that maintains the correct magnitude of the area of objects and surfaces. The script does not provide a specific example, but the concept is important for maps where area accuracy is critical.

💡Equidistant Projection

Equidistant projections are characterized by maintaining the correct ratio of distances between two points. The script mentions this type of projection as one that preserves distance relationships, which is important for navigation where distance accuracy is key.

💡Azimuthal Projection

Azimuthal projections are designed to preserve the direction between two points. The script describes this projection as having no distortion at the center point, typically over the poles, but increasing distortion as one moves away from the center, making it suitable for polar regions but not common for navigation.

💡Cylindrical Projection

Cylindrical projections, such as the Mercator projection mentioned in the script, involve a piece of paper wrapped around the earth and touching at the equator. These projections are characterized by accurate scale along the equator but increasing distortion in shape and size as one moves away from it, as exemplified by the misrepresentation of the sizes of Africa and Greenland.

💡Conical Projection

Conical projections are created by folding a piece of paper into a cone shape and touching the earth at two standard parallels. The script explains that these projections are accurate at the points of contact but distort in size and shape as one moves away from these standard parallels, similar to cylindrical projections.

Highlights

Cartography is the science of graphically representing the earth's surface at a smaller scale on a 2D surface like paper.

A chart is a specialized type of map designed for a specific purpose, such as nautical or aeronautical navigation.

Representing the 3D earth on a 2D surface without distortion is impossible, requiring the use of projections.

Projections are attempts to represent the earth's surface on developable shapes like cylinders or cones for 2D representation.

Different projections preserve different properties such as shape, area, distance, or direction.

No single projection can preserve all properties simultaneously, necessitating a choice based on the map's purpose.

Projections can be visualized as the earth's surface being projected onto paper wrapped around it.

Azimuthal projections have no distortion at the center point but increasing distortion away from it.

Cylindrical projections show no distortion at the equator and increasing distortion towards the poles.

Conical projections have accurate scale and shape at standard parallels but distort size away from these points.

Projections can be arranged differently to map specific areas accurately, depending on the region's characteristics.

Commonly used navigation projections include the Lambert Conformal Conic and the Mercator Conformal Cylindrical.

Air navigation charts focus on small areas to minimize distortion for specific flights, requiring multiple charts.

Scale is the relationship between a map measurement and the actual earth measurement, calculated as real distance divided by map distance.

Maps publish their scale in various formats, aiding in determining distances without specialized tools.

Examples are provided to demonstrate how to calculate real distances using map scales and rulers.

Understanding scale is crucial for accurate navigation and interpretation of map measurements.

The video concludes with an encouragement to share, like, subscribe, and comment for further engagement.

Transcripts

today we will talk about cartography

projections and scales which are

essential concepts for the proper

interpretation of navigation charts

so let's start by defining cartography

this word comes from cardo which means

map and graph which means right and it

is the science of representing a part or

all of the earth's surface graphically

at a smaller scale in a 2d surface such

as a piece of paper

this graphic representation obtained is

called a map

but why do we sometimes say map and

sometimes chart

well a chart is actually a type of map

let's look at this in more detail

in general terms a chart is a

specialized map which contains

information related to a particular

purpose

for example a nautical chart will show

information such as seed depth

lighthouses ports and so forth since its

purpose is to assist the navigation of

ships

however in the case of aviation an

aeronautical chart is a map adapted to

the needs of air navigation which

contains detailed relevant information

on the most important aspects such as

obstacles navaids airports air spaces

etc

now with this being said when we try to

create a map or chart that correctly

represents the surface of the earth we

run into a big problem and it is that

representing a 3d figure such as the

earth in a 2d surface is extremely

complicated

since it is impossible to represent the

earth on a 2d plane maintaining all its

proportions scales and features

correctly

however we can try to get as close to

perfection as possible

to try to do this the earth's surface

must be projected into shapes that can

actually be represented in a 2d surface

such as cylinders or cones which are

developable surfaces

now all these attempts to represent the

earth in different shapes are known as

projections and there are a lot of

them each projection receives its name

depending on its characteristics and the

properties it preserves

for example a conformal projection

maintains the correct shape of objects

and surfaces

an equivalent projection maintains the

magnitude of the area of objects and

surfaces correctly

an equidistant projection maintains the

ratio of the distance between two

objects or surfaces correctly

and an azimuthal projection maintains

the direction between two objects or

surfaces correctly

now although it would be great to be

able to include all of these features on

the same map there is no existing

projection that preserves all of these

characteristics at the same time

so it must be decided which of these

features is more important to include in

the map depending on its purpose

now to understand better how a

projection is developed it can be

described as putting a light bulb in the

center of the earth in a piece of paper

around the planet

then when the light bulb is turned on

the surface of the earth is projected

onto the piece of paper becoming a map

this way the resulting map will depend

on how the paper is placed around the

earth and that is why there are

different types of projections

now an important thing regarding this is

that in all types of projections there

is one or more points where the paper

touches the surface of the earth and as

a general rule these points where the

projection touches the surface are the

most accurate and precise in terms of

scale distance direction shape etc and

as we move away from these points the

map begins to distort

so with this being said let's take a

look at the most commonly used

projections starting with the azimuthal

projection

it consists of a flat piece of paper

that touches the earth at one of its

poles as we can see in this images

the main characteristics of an azimuthal

projection is that near the center point

there is no distortion the magnitude of

the distortion increases as we move away

from the center point and direction and

distance can only be measured correctly

from the center point

this projection is often used to map the

poles but is not commonly used for

navigation

now the next one is the cylindrical

projection which consists of a piece of

paper that is folded into a cylinder

shape and touches the earth around the

equator as we can see in these images

in this case the projection touches the

earth around the entire equator line

therefore the main characteristics of

this cylindrical projection are that

near the equator there is no distortion

the magnitude of the distortion

increases as we move away from the

equator

meridians in parallels intersect at 90

degrees angles making it easier to

measure direction and it shows the

shapes correctly but the size is

distorted

a clear example of this is the

representation of africa and greenland

here we can clearly see that in reality

africa is much bigger than greenland

however because of the distortion of

this cylindrical projection it looks

like it is almost the same size

finally there is the conical projection

which consists of a piece of paper that

is folded into a cone shape and touches

the surface in two particular parallels

which are known as standard parallels as

we can see in these images

in this case since there are two points

at which the projection touches the

surface in both of them the

characteristics and properties are

accurate and correctly preserved giving

as a result this pattern of distortion

now the main characteristics of this

conical projection are that near the

standard parallels there is no

distortion the magnitude of the

distortion increases as we move away

from these standard parallels and it

shows the shapes correctly but the size

is distorted just like in the

cylindrical projection

here we can see an example of how a map

is developed using this conical

projection

finally something important to mention

is that a projection can be arranged in

different ways depending on the area to

be mapped accurately as we can see in

these examples

now regarding the names of the

projections they consist of a

combination of their creator their main

characteristic and technique used for

example the most used projections for

navigation are the lambert conformal

conical and the mercator conformal

cylindrical

in these cases to avoid excessive

distortion the charts used for air

navigation focus on relatively small

specific areas

and therefore for a certain flight

several charts may be required

let's now move on to the scale

on an aeronautical chart it is important

that the proportions of terrain and

objects are correctly maintained

and the scale is the relationship

between a measurement on the map or

chart and the actual measurement on the

earth

and its formula is very simple it is

real distance divided by the map

distance

now all maps publish the scale with

which they were designed and this can be

found in different formats

for example they can publish a numerical

scale or a graphic scale or even a plain

text scale

here we can see some examples of how the

scale is published on a map

this information is really useful when

we have to determine distances on a map

without a plotter

let's see an example of how to do this

let's say we have this chart with a

scale of one in one million and we want

to determine the distance between the

towns of germania and miraflores

however we don't have a plotter so we

have to use a regular ruler that

measures centimeters

according to this we measure a distance

on the map of 16 centimeters

so now the question is with this

information how can we determine the

real distance between these towns

well we have to use the scale formula

which is real distance divided by map

distance

right now we know the scale and the map

distance so we just have to rearrange

the formula to determine the real

distance which in this case is 16

million centimeters

with this we already know the real

distance but it is in centimeters so we

must convert units to nautical miles

obtaining as a result a distance of 86.4

nautical miles

in this example we used a map with a

scale of one in one million

let's see now another example but now

with a scale of 1 in hundred and fifty

thousand

in this case we want to determine the

real distance between the towns of san

jose and esmeralda which are twelve

centimeters apart on the map

so to do this we use the previous

formula to determine the real distance

which in this case is 3 million

centimeters

then we convert units to get nautical

miles obtaining as a result a real

distance of 16.2 nautical miles between

san jose and esmeralda

now normally we have available a plotter

graduated with statute and nautical

miles so we don't have to do this

procedure

however it helps to understand the

concept of scale

i hope the information presented in this

video was useful

if so don't forget to share like

subscribe and leave a comment down below

thanks for watching

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