Ppt Gis Lecture 1.0

8/12/2019 Ppt Gis Lecture 1.0

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Mudit Kapoor


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GIS present a simplified view of the world asit would be impossible to represent reality inits entirety in a computer

The simplified view of the real world adoptedby GIS is often termed a model

Data are observations we make frommonitoring the real world

Data falls in two categories: Primary

Secondary

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Primary Data: Data through first hand observation

Counts of skiers using a particular ski run

Secondary Data Data collected by individual, organization, etc

Consumer survey of customers buying skiequipments

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Sources of primary and secondary data usedin Happy Valley

Primary Data Daily meteorological records

No. of lift passes

No. of avalanches recorded

Secondary Data Published meteorological maps

Local topographic maps

National and regional lifestyle data

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Temporal(When) Thematic(Features of one type that are generally

placed together in a single layer)

Spatial(co-ordinate, spatial referencing)

For ex., for data about avalanche accident whichtook place in Three Pines Valley on 14 February,1995, three modes are:

Temporal- 14 February 1995;

Thematic- avalanche accident; and

Spatial-Three Pines Valley

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Source of data Sketch map: going to some place

Topographic and thematic maps that can befound in national atlases

Thematic Map: Special purpose map, show data related to a

particular theme/ topic

Eg. Soil, geology, land use, population, transport

Topographic Map: General purpose Maps

Contains a diverse set of data on different themes

Land use, relief and cultural features map all appear

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Establish the purposethe map is to serve; Define the scaleat which the map is to be Select the features(spatial entities) from the

real world which must be portrayed on the

map Choose a method for the representationof

these features (point, lines and areas) Generalizethese features for representation

in two dimensions; Adopt a map projection for placing these

features onto a flat piece of papers;

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Apply spatial referencing system to locatethese features relative to each other; and

Annotatethe map with keys, legends and textto facilitate use of the map

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Purpose Scale

Ratio 1:5,000 1:1,000,000

Verbal(nominal) 1 cm > 50m 1 cm >10 KM

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Ppt Gis Lecture 1.0

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