scale,resolution,types

8/10/2019 Scale,Resolution,Types

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SCALE

"Scale" which indicates the relationship between a distance on the map and the

distance on the ground.

The map scale is usually located in the legend box of a map, which explains the

symbols and provides other important information about the map

RF - Ratio or Representative Fraction indicates how many units on the earth's surface is

equal to one unit on the map. It can be expressed as 1/100,000 or 1:100,000. In this example,

one cm on the map equals 100,000 cm (1 km) on the earth. It also means that one inch on the

map is equal to 100,000 inches on the land.

Maps are often two types:

Large scale

Small scale.

Medium scale

A large scale map refers to one which shows greater detail; objects are relatively

large because the representative fraction (e.g. 1/25,000) is a larger fraction

A small scale map ,where objects are relatively small which would have an RF of

1/250,000 to 1/7,500,000.

Large scale maps will have a RF of 1:50,000 or greater (i.e. 1:10,000). Those

between 1:50,000 to 1:250,000 are maps with an intermediate scale or medium scale

maps.

Ex:

1. For example a town planner who is used to working with plans at 1:1000, may

consider 1:25 000 a small scale map.

2. atlas compiler commonly working with maps of scales 1:5 000 000 would consider

1:25 000 a large scale map.

To understand the use of the terms, the ratio method of showing map scale:


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The ratio 1:10 000 - means that the size of objects on the map is 1/10 000 of

their size on the ground..

Large scale map Small scale map

Large scale maps show a small area

in greater detail

Small scale maps show a larger area in

less detail.

They are guide maps or topographic

maps.

They are wall maps, or atlas maps.

Details of cities, towns, villages are

shown.

They show important features like

mountains, plateaus,

continents and countries,etc.,

The scale may be 1 cm = 50 m or 1

km.

Scale may be 1 cm = 100 km

REFERENCE :

1. http://geography.about.com/cs/maps/a/mapscale.htm

2.

http://eps.mq.edu.au/courses/GEOS264/maps/mapch2/lscale.htm
http://geography.about.com/cs/maps/a/mapscale.htmhttp://geography.about.com/cs/maps/a/mapscale.htmhttp://eps.mq.edu.au/courses/GEOS264/maps/mapch2/lscale.htmhttp://eps.mq.edu.au/courses/GEOS264/maps/mapch2/lscale.htmhttp://eps.mq.edu.au/courses/GEOS264/maps/mapch2/lscale.htmhttp://geography.about.com/cs/maps/a/mapscale.htm


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RESOLUTION

GeneralComputing :

The smallest spacing between two display elements, expressed as dots per inch, pixels per

line, or lines per millimeter.

Cartography :

The detail with which a map depicts the location and shape of geographic features. The larger

the map scale, the higher the possible resolution. As scale decreases, resolution diminishes

and feature boundaries must be smoothed, simplified, or not shown at all; for example, small

areas may have to be represented as points.

GIS :

Refers to how accurately the location and shape of map features can be depicted at a given

scale.The resolution of digital images can be described in many different ways.

Pixel resolution

An image of N pixels high by M pixels wide can have any resolution less than N

lines per picture height, or N TV lines.

When the pixel counts are referred to as resolution, the convention is to describe

thepixel resolutionwith the set of two positive integer numbers, where the first

number is the number of pixel columns (width) and the second is the number of pixel

rows (height), for example as 640 by 480.

Another popular convention is to cite resolution as the total number of pixels in the

image, typically given as number of megapixels, which can be calculated by

multiplying pixel columns by pixel rows and dividing by one million.

Other conventions include describing pixels per length unit or pixels per area unit,

such aspixels per inch or per square inch. None of thesepixel resolutions are true

resolutions, but they are widely referred to as such; they serve as upper bounds on

image resolution.

Below is an illustration of how the same image might appear at different pixel resolutions, if

the pixels were poorly rendered as sharp squares (normally, a smooth image reconstruction
http://wiki.gis.com/wiki/index.php?title=Pixels_per_inch&action=edit&redlink=1http://wiki.gis.com/wiki/index.php?title=Pixels_per_inch&action=edit&redlink=1


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Spectral resolution

Spectral resolution describes the ability of a sensor to define fine wavelength

intervals. The finer the spectral resolution, the narrower the wavelength range for a

particular channel or band

Spectral resolution

here the finer spectral resolution is colour film.

Many remote sensing systems record energy over several separate wavelength ranges

at various spectral resolutions. These are referred to as multi-spectral sensors

Advanced multi-spectral sensors called hyperspectral sensors, detect hundreds of

very narrow spectral bands throughout the visible,near-infrared, and mid-infrared

portions of the electromagnetic spectrum. Their very high spectral resolution

facilitates fine discrimination between different targets based on their spectral

response in each of the narrow bands.

Temporal resolution

The concept of revisitperiod, which refers to the length of time it takes for a satellite

to complete one entire orbit cycle. The revisit period of a satellite sensor is usually

several days. Therefore the absolute temporal resolution of a remote sensing system to


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image the exact same area at the same viewing angle a second time is equal to this

period.

The actual temporal resolution of a sensor depends on a variety of factors, including

the satellite/sensor capabilities, the swath overlap, and latitude.

Temporal resolution

The ability to collect imagery of the same area of the Earth's surface at different

periods of time is one of the most important elements for applying remote sensingdata.

Spectral characteristics of features may change over time and these changes can be

detected by collecting and comparing multi-temporal imagery. For example, during

the growing season, most species of vegetation are in a continual state of change and

our ability to monitor those subtle changes.

Radiometric resolution The arrangement of pixels describes the spatial structure of an image, the radiometric

characteristics describe the actual information content in an image.

Every time an image is acquired on film or by a sensor, its sensitivity to the

magnitude of the electromagnetic energy determines the radiometric resolution.

The radiometric resolution of an imaging system describes its ability to discriminate

very slight differences in energy .

The finer the radiometric resolution of a sensor, the more sensitive it is to detecting

small differences in reflected or emitted energy.


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Radiometric resolution determines how finely a system can represent or distinguish

differences ofintensity,and is usually expressed as a number of levels or a number

ofbits,for example 8 bits or 256 levels which is typical of computer image files.

The higher the radiometric resolution, the better subtle differences of intensityorreflectivity can be represented, at least in theory. In practice, the effective

radiometric resolution is typically limited by the noise level, rather than by the

number of bits of representation.

Coarser resolution Finer resolution

References :

1. http://wiki.gis.com/wiki/index.php/Image_resolution

2. http://www.cedareden.com/cdea/gis/scale/frame.html

3. http://support.esri.com/en/knowledgebase/GISDictionary/term/resolution
http://wiki.gis.com/wiki/index.php?title=Intensity&action=edit&redlink=1http://wiki.gis.com/wiki/index.php/Bithttp://wiki.gis.com/wiki/index.php?title=Reflectivity&action=edit&redlink=1http://wiki.gis.com/wiki/index.php/Image_resolutionhttp://wiki.gis.com/wiki/index.php/Image_resolutionhttp://www.cedareden.com/cdea/gis/scale/frame.htmlhttp://www.cedareden.com/cdea/gis/scale/frame.htmlhttp://support.esri.com/en/knowledgebase/GISDictionary/term/resolutionhttp://support.esri.com/en/knowledgebase/GISDictionary/term/resolutionhttp://support.esri.com/en/knowledgebase/GISDictionary/term/resolutionhttp://www.cedareden.com/cdea/gis/scale/frame.htmlhttp://wiki.gis.com/wiki/index.php/Image_resolutionhttp://wiki.gis.com/wiki/index.php?title=Reflectivity&action=edit&redlink=1http://wiki.gis.com/wiki/index.php/Bithttp://wiki.gis.com/wiki/index.php?title=Intensity&action=edit&redlink=1

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