Geography Chapter 2

Being able to register different info in a common database allows

one map layer, such as rivers, to be cross referenced to another, such as geology soils, or slope

What are interrupted projections?

one technique used with pseudocylindrical projections to minimize distortion of the continents is to "interrupt" oceanic regions

When and where does distortion occur in pseudocylindrical projections

distortions in size and/or shape normally increases progressively as one moves away from this point in any direction

Isolines are an artificial construct

do not occur in nature

In the pseudocylindrical projections, all of the parallels are

drawn parallel to each eather

What are conic projections particularly well adapted for

mapping relatively small areas, such as a state or country

What are planar projections useful for?

mapping the Arctic or Antarctic circle and focusing attention on specific regions

What is often the first essential step toward understanding the spatial distributions and relationships of geographic features?

mapping them

How are most map projections created today?

mathematically transferred the features from the sphere to a flat surface

Knowing the scale of the map makes it possible to

measure distance, determine area, and compare size

What does thermal scanning do?

measures the radiant temp of objects and may be carried out either day or night

All conformal projections have ____ and ____ crossing each other at right angles

meridians and parallels

The greatest use for thermal IR scanning systems has been

meteorological satellites and weather forecasting

What is thermal infrared?

middle or far infrared part of the electromagnetic spectrum

Why are equivalent map projections desirable?

misleading impressions of size are avoided

There are appx how many different kinds of isolines?

more than 100

Typically, planar projections show only

one hemisphere

What is the most important active sensing used in Earth sciences?

radar

What are these photos good for?

showing diurnal temp differences between land and water, between bedrock and alluvium, for studying thermal water pollution, for detecting forest fires

In the pseudocylindrical projects, all meridians, except the central meridian are

shown as curved lines

The advantage of a graphic map scale

simplicity and it remains correct when the map is enlarged or reduced in size

Is there size distortion anywhere else on these maps?

size distortion increases progressively with increasing distance from this circle

The other active remote sensing system is

sonar

Sonar is

sound navigation and ranging that permits underwater imaging

Some isolines represent tangible surfaces, such as

the elevation contour lines on a topographic map

What is the best way to show the Earth as a whole

the globe

GIS's are libraries of info that use maps to organize store, view, and analyze info in an intuitive, visual manner. Just as an ordinary computer database management system can manipulate rows and columns of data in tabular form, the GIS allows data management using

the link between data and the map

Most important tool of a geographer?

the map

The north arrow points to

the north pole

The greater the number of channels in a GPS unit, the greater

the number of satellites that can be tracked and the better accuracy

What is one of the great virtues of digital elevation?

the parameters of the image can be readily manipulated

The map scale describes

the relationship between distance measured on a map and the actual distance that represents the Earth's surface

How do we use it today?

the same way

What is photogrammetry?

the science of obtaining reliable measurements and mapping from aerial photographs

Using the Mercator map will allow a navigator to generally take

the shorter path of a great circle route by simply making periodic changes in the compass course

What is the problem with conformal projections?

the size of an area must often be considerably distorted to depict proper shape. The scale will have to change from one region to another

This parallel that coincides with the circle of tangency becomes known as

the standard parallel of the projection

The focus of the geographer is

the surface of the earth

Data source is important in

thematic maps. It is useful to indicate the source of the data

What needs to be understood no matter how map projections are done?

there will always be distortion of shape, relative area, distance, and/or direction. You can control some of these but never all

The basic characteristics of Isolines include

1) always closed lines; that is they have no ends 2) because they represent gradations in quantity, they can never touch or cross one another 3) the numerical difference between one isoline and the next is called the interval 4) isolines close together indicate a steep gradient (in other words, a rapid change); isolines far apart indicate a gentle gradient

The extent to which the geometric impossibility of flattening a sphere without distortion becomes a problem on a map depends on two related variables

1) how much of Earth is being shown on the map (ex: these distortions are always significant on a world map, but less so on a map showing a very limited region of the Earth) 2) the scale of map

What are some ways vertical landscape is portrayed on maps?

1) raised relief models 2) elevation contours 3) digital elevation models

The first published map to include isolines

1700; Edmund Halley, not the first time isolines were used, but first time published

How many satellites are currently active

31 with backups

Landsat 7 carries an instrument array call the Enhance Thematic Mapper Plus that provides images in eight spectral bands with a resolution of 15 meters (49 feet) in the panchoromatic band in the 6 narrow bands of visible and short infrared wavelengths, and 60 meters (197 feet) in thermal infrared.

Just read over this one

Distortion in conic projections?

distortions are least in the vicinity of the circle of tangency and increases progressively as we get farther away

Because a map is smaller than the portion of Earth's surface it represents, in order to understand the geographic relationships depicted on that map, we must know how to use

a map scale

What is a thematic map?

a map with a theme. For example, street patterns

The digital multispectral satellite image is conveyed through

a matric of numbers, each representing a single value for a specific pixel and band

So how does one use the Mercator map?

a navigator first plots the shortest distance between origin and destination on a map projection in which great circles are shown as straight lines and then transfers them to a Mercator projection with straight line loxodromes.

Several dozen ground based station across North America monitor GPS signals fro the satellites and then generate a correction message that is transmitted to the GPS units. With WAAS, the GPS units achieve

a position of accuracy of 3 meters (about 10 feet) about 95% of the time

If the map is of a small area, how many scales should be used?

a single scale will most likely do it.

What is map projection?

a system in which the spherical surface of Earth is transformed for display on a flat surface

You cannot sense thermal infrared with

conventional digital cameras or traditional photographic film

What is the down side of equivalence?

difficult to achieve on small scale maps because correct shapes must be sacrificed in order to maintain proper area relationships

A multispectral satellite image is

digital

This allows what to happen to the shapes on the maps?

allows the shapes to be approximated with reasonable accuracy

What is a loxodrome?

also called a rhumb line, a curve on the surface of a sphere that crosses all meridians at the same angle and represents a line of constant compass direction

What is pseudocylindrical projection

also called elliptical or oval projection, roughly football shaped map, usually of the entire world, although sometimes only the central section of a pseudocylindrical projection is used for maps of lesser areas

Maps can display data many different ways. One of the most widespread techniques for portraying the geographic distribution of some phenomenon is isoline. Isoline is a generic term that refers to

any line that joins points of equal value of something

Mathematically, a pseudoclylindrical projection wraps how?

around the equator like an ordinary cylindrical projection, but then further curves in toward the poles, effectively conveying some of the curvature of Earth

How was this kind of imagery used in WWII?

as camouflage detection because it was able to discriminate between living vegetation and the vegetation used to hide objects during the war

An example of a fraction in a fractional map scale

1/63,360 or 1:63,360: this notation means that 1 unit measure on the map represents an actual distance of 63,630 units on earth

Even the simplest GPS units determine position to within

15 meters (49 feet)

The Mercator projection was created in _____ and is till the go to for many, most famous map

1569

What is conformality?

A conformal map projection is one in which proper angular relationships are maintained across the entire map so that the shapes of features such as coastlines are the same as on Earth

What is isobar?

A line joining points of equal atmospheric pressure

What are elevation contour lines?

A line on a map joining points of equal elevation

How is a verbal map scale similar to a fractional map scale?

A verbal scale is a mathematical manipulation of the fractional scale. Ex: there are 63,360 inches in a mile, so on a map with a fractional scale of 1:63,360, we can say 1 inch represents 1 mile

What is a verbal map scale?

Aka: word scale, states that in words the relationship between the distance on the map and the actual distance on Earth's surface, such as "one centimeter to ten kilometers"

Why do we need a scale?

Any map that serves as more than a pictogram must be drawn to scale, appx. Because of this, a graphic, verbal, or fractional scale is necessary

What is Landsat?

Early NASA space missions used multiband photography obtained through mulitcamera arrays. These imaging experiments were so successful that NASA then developed what was initially called Earth Resources Technology Satellite series (ERTS) and later renamed Landsat

It is impractical to use conic projections when?

For more than 1/4 of Earth's surface (semihemisphere)

An example of interruped projections?

Goode's interrupted homolosine equal-area projection

What is equivalence?

In an equivalent map projection or equal area map projection, the correct size ratio of area on the map to the corresponding actual area on Earth's surface is maintained over the entire map

What is unique about radar?

It can penetrate atmospheric moisture

What kind of projection can we clearly see this issue?

Mercator projection

Is there size distortion at the circle of tangency?

No

Planar projection and distortion?

No distortion immediately around the point of tangency but increases as you move away from this point

What is a large scale map?

One that has a relatively large representative fraction or the denominator is smaller

What is a small scale map?

One that has a relatively small representative fraction or the denominator is larger

What if we have a map that wants to emphasize oceans?

Then we can interrupt landmasses

What is the Continuously Operating GPS Reference Stations (CORS)

They are permanently installed GPS receiving stations managed by the National Oceanic and Atmospheric Administrations. Highly accurate units that are capable of detecting location differences of less than 1 centimeter of latitude, longtitude, and elevation. Used for the long term monitoring of slight changes in the ground and surface caused by lithospheric plate movement or the bulging of magma below a volcano

So what does conformality achieve?

They show correct shapes on a map. It is impossible to depict true shapes for large areas such as a continent, but they can be approximated, and in practice for small areas we can say conformal maps show correct shapes

What can increase GPS accuracy when _____ ____ ________ _____ is employed

Wide Area Augmentation System (WAAS)

What kinds of other wavelengths of energy are there?

X-rays, ultraviolet radiation, infrared radiation, radio waves

Are GPS's more accurate than the best base maps?

Yes

How do you use a graphic map scale?

You measure off the distance between two points on the map and then convert using the graphic map scale

What is an example of a compromise map projection?

a Robinson projection

The title of a map should be

a brief summary of the map's content or purpose. Should identity the area covered and provide some indication of content

Where is the point of no distortion in pseudocylindrical projections?

a central parallel (usually the equator) and central meridian (often the prime meridian) cross at right angles in the middle of the map

Except for maps of very small areas, where both properties can be closely approximated, conformality and equivalence cannot be maintained on the same projection, and thus the art of mapmaking is often an art of compromise. What kind of projection is neither equivalent nor conformal, but instead balances reasonably accurate shapes with reasonably accurate areas?

a compromise map projection

What is the Mercator projection?

a conformal map projection designed to facilitate oceanic navigation

The GPS system is based on

a constellation of at least 24 high altitude satellites configured so that a minimum of four or six are in view of any position on Earth. These satellites continuously transmit both identification and positioning info that can be picked up by receivers on Earth

Using the graphic map scale will give you

a direct reading of actual distance

What is a map?

a flat representation of Earth, shown reduced in size with only selected features or data showing

What is the Global Positioning System (GPS)

a global navigation satellite system for determining accurate positions on or near Earth's surface developed in the 70's and 80's by the US Department of Defense to aid in navigation aircraft, guiding missiles, and controlling group troops

What is an elevation contour line?

a line joining points of equal elevation

What is the isogenic line?

a line joining points of equal magnetic decliniation

What is Isohyet?

a line joining points of equal quantities of precipitaiton

What is isotherm?

a line joining points of equal temp

A well made globe

accurately convey's the spherical shape of the Earth as well as show without distortion, the spatial relationships of Earth's surface, while maintaining correct size, shape, distance, and direction relationships of features around the planet

What was the only form of remote sensing that was used for geographic purposes until the 60's?

aerial photography

Scale can never be perfectly correct over an entire map, why?

because the Earth's surface is curved and map's are flat

How have computers changed geography?

cartographers have been working since the early days of the Egyptians but with the intro of computer, they have advanced passed drawings. Computers have provided improvements in speed and image handling ability

When a projection is interrupted, it will be based on

central meridians that pass through each major landmass - with no land area far from a central meridian

Can be used to

collect, store, retrieve, reorganize, analyze, and map geographic data from the real world

How does FEMA use it?

collecting data, damage assessment following natural disasters as floods and hurricanes

The distance between a receiver and each member in a group of four or more satellites is calculated by

comparing clocks stored in both units, and then the 3D coordinates of the receiver's position are calculated thru triangulation

What is a digital elevation model?

computer generated shaded relief image of a landscape derived from a database of precise elevation measurements

It is impossible for this map to be

conforomal

A globe does have limitations

constructed at a very small scale and can't show much detail

GPS has been used in

earthquake forecasting, ocean floor mapping, volcano monitoring and a variety of other mapping projects

Cartographers often strive to maintain accuracy either of size or shape using map properties known as

equivalence and conformality

What do satellites do?

gather data, produce images that provide communications, global positioning, weather data, and a variety of other info for a wide range of commercial and scientific applications

The most revolutionary technological advance in cartography in the last few decades has been

geographic information systems (GIS)

There are three ways to portray map scales that are widely used

graphic scale, fractional scale, and verbal scale

Orthophotos can show the landscape how due to displacements being removed?

greater detail

What is an active system?

has its own source of electromagnetic radiation

How did Mercator attempt to maintain conformality and the maps navigational virtues?

he compensated for the east/west stretching by spacing the parallels of latitude increasingly farther apart so that north/south stretching occurs at the same rate

Notating projection type will

help the user assess the kinds of distortions on the map

Although traditional photographic film was sensitive to only a narrow band of visible radiation, a satellite equipped with a multiband instrument images the surface of the earth

in several spectrum regions at once - visible light, near infrared, middle infrared, and thermal infrared - each useful for different applications

WAAS was implemented to

increase the accuracy of instrument-based flight approaches for airplanes

The date of a map should

indicate the time span over which the info was collected, maybe the publication date. Because most maps depict conditions or patterns that are temporary or even momentary, for the map to be meaningful, the map should indicate when the data were gathered.

GPS is inexpensive/expensive?

inexpensive

When global distributions are mapped, the continents are often more important than the oceans, and yet the oceans occupy most of the map space in a typical projection. A projection can be

interrupted or torn apart

By doing this, shape and size distortion

is greatly decreased

What kind of electromagnetic spectrum can the naked eye see?

is only sensitive to a narrow portion known as visible light, colors seen in a rainbow

What is a fractional map scale

it conveys the relationship between distance measured on the map and the actual distance that represents on Earth with a fraction or ratio

What is the prime advantage of a Mercator map?

it shows loxodromes as straight lines

Why a direction indicator?

it's normally shown on a map by means of a geographic grid of parallels and meridians. If no grid is shown, direction may be indicated by a straight arrow pointing north

What is a cylindrical projection

its obtained by mathematically "wrapping" the globe with a cylinder of paper in such a way that the paper touches the globe only at the globe's equator

What is the most common system of location?

longitude and latitude

Multispectral instruments detect and record

many bands of the electromagnetic spectrum simultaneously

Why is the legend necessary?

most maps use symbols, colors, shadings, or other devices to represent features or the amount, degree, or proportion of some quantity. Although some symbols are self explanatory, it is usually necessary to include a legend to help explain the symbolization

What are orthophoto maps?

multicolored distortion free photographic maps prepared from aerial photographs or digital images

Today, most sophisticated remote sensing satellites are

multispectral or multiband

With color IR imagery, sensitivity to visible blue light is replaced by sensitivity to

near infrared wavelengths

Maps have limitations as well

no map can be perfectly accurate because it is impossible to portray the curved surface of Earth on a flat map without distortion

This arrow that points north is also known as

north arrow

What are conic projections

obtained by projecting the markings of a center lit globe onto a cone wrapped tangent to, or intersecting, a portion of the globe. Normally, the apex of the cone is positioned above a pole, which means that the circle of tangency coincides with a parallel.

What is a planar projection?

obtained by projecting the markings of a center-lit globe onto a flat piece of paper that is tangent to the globe at one point, usually the north or south pole, or some point on the equator.

This means the data and map are encoded, usually as numbers representing coordinates of locations at point on a grid covering the mapped area. Once the data and the map are inside the GIS, the user can

organize or search the data using the map, or the map using the data

What does suffer with this action?

proper size relationship

What is radar?

radio detection and ranging; senses wavelengths longer than 1 millimeter using the principle that the time it takes for an emitted signal to reach a target and then return to the sender can be converted to distance info

What is remote sensing?

refers to any measurement of acquisition of info by a recording device that is not in physical contact with the object under study

Conic projects are best suited for?

regions of east/west orientation in the midlatitudes

How is the distortion on a Mercator map?

relatively undistorted in the low latitudes and increases rapidly in the mid and high altitudes because the meridians do not converge at the poles but instead remain parallel to each other

This fraction used in fractional map scale is called

representative fraction

What has revolutionized remote sensing?

satellites!!

All the remote multispectral sensing systems up to this point work by

sensing the natural radiation emitted by or reflected from an object and are therefore characterized as passive systems

The data from the digital multispectral satellite image is

stored in the satellite, eventually transmitted to an Earth receiving station, numerically processed by a computer, and produced as a set of grey values and/or colors on a screen or hard copy printout

Orthophoto maps are particularly useful in flat lying coastal areas because they can show

subtle topographic detail in areas of very low relief, such as marshlands

What do we use instead?

supercooled snanners

This type of wrapping, we say it is _______ to the globe at the equator and the equator is called the ______ __ _______

tangent; the circle of tangency

Some isolines represent intangible features such as

temperature and precipitation, and some express relative values such as ratios or proportions

Radar imagery is particularly useful for

terrain analysis in places of frequent cloud cover or thick vegetation, and for meteorology, especially in the real time study and mapping of rainfall and severe weather

What is GIS?

the computer systems designed to analyze and display spatial data

If the map is showing large portions of the Earth's surface, what happens to the map scale?

there will be significant scale differences from one part of the map to the other and may need different scales for different latitudes

What about scale and precision?

they retain the map characteristic of a common scale that allows precise measurement of distances

In cylindrical projection, what happens to the curved parallels and meridians

they will form a perfectly rectangular grip on the map and having the equator as the tangency line produces a right angled grid (meridians and parallels meet at right angles) on a rectangular map

What is a raised relief model?

three dimensional

Every map should contain these things

title, date, legend, scale, direction, location, data source, and projection type

One important attribute is the capability of GIS data from different maps and sources, such as field data, map data, and remotely sensed images, to be registered

together with a common database, with a common map scale and map projection

How was GPS used at Ground Zero?

used by workers to catalog items found in the enormous heaps of rubble following the WTC disaster 9/11/01

What is isoamplitude?

used to describe radio waves

What is a graphic map scale?

uses a line marked off in distances to represent actual distance on Earth's surface

What is color infrared imagery?

uses electronic sensors or photographic film sensitive to radiation in the near infrared portion of the electromagnetic spectrum - wavelengths of radiation just longer than the human eye can see

These images, even though they are false color images, are

valuable

The shapes of continental coastlines, in interrupted projections are

very well maintained even in high latitudes

What is isovapor?

water vapor content in the air

One of the most important advancements in remote sensing came when what was first used?

wavelengths of radiation other than visible light

The map is good for showing

what is where: distance, direction, size, shape in horizontal, or two dimensional, spatial relationships

What is elecromagnetic radiation?

wide range of wavelengths of energy emitted by the Sun and other objects

What other ways do maps help individuals find location?

x and y grids