Civil - Remote Sensing Techniques and GIS - Geographic Information System
GEOGRAPHIC INFORMATION SYSTEM
1.What is map?
A map is usually considered to be a drawing to scale of the whole or a part of the surface of the earth on a plane surface; it is a manually or mechanically drawn picture of the earth showing the location and distribution of various natural and cultural phenomena.A map is a symbolic representation of an area.
2.Write the two types of maps?
The two maps are topographical and thematic maps.
3.Write about topographical map?
It is a reference tool, showing the outlines of selected natural and man-made features of the Earth
often acts as a frame for other information
"Topography" refers to the shape of the surface, represented by contours and/or shading, but topographic maps also show roads and other prominent features. 4.Write about thematic map?
It is a tool to communicate geographical themes such as, the distribution of population & densities, climatic variables and land use etc.
5.What are the thematic maps in GIS?
b) area class map
c) isopleth map
6.What are the characteristics of map?
maps are often stylized, generalized or abstracted, requiring careful interpretation
usually out of date
show only a static situation - one slice in time
often highly elegant/artistic
easy to use to answer certain types of questions:
how do I get there from here?
what is at this point?
difficult or time-consuming to answer other types:
what is the area of this lake?
what places can I see from this TV tower?
what does that thematic map show at the point I'm interested in on this topographic map?
7.Write the necessity of map projection?
Projection is necessary one because spatial entities locate in two dimensions. The method by which the world is laid flat is use to help projection. Doing the process introduce error into spatial data. Spatial data character varies depending on the projection method chosen. Shape and distance are distorted the accuracy world is spherical shape visualize the two dimension in flat surface is difficult.
8.Write the types of map projection?
1.Cylindrical projection 2. Azimuthal projection 3. Conical projection
9.Write few lines about cylindrical projection? Countries near the equator in true relative portion
Distance increases between countries located towards top and bottom of mage. The view of the poles is very distorted
Area for the most part is preserved 10.Write few lines about conical projection?
Area is distorted.
Distance is very distorted towards the bottom of the image. Scale for the most part is preserved
11.Write few lines about azimuthal projection? Only a part of the earth surface is visible.
The view will be of half the globe or less. Distortion will occur at all four edges. Distance for the more part is preserved.
12.What is referencing system?
Referencing system is used to locate a feature on the earths surface or a two dimension representation of this surface such as a map.
13.What are the methods of spatial referencing systems?
Several methods of spatial referencing exist all of which can be grouped into three categories.
Geographical co-ordinate system Rectangular co-ordinate system Non-co-ordinate system
14. What is Geographic Co-Ordinate System?
This is a one of true co-ordinate system .the location of any point on the earth
surface can be defined by a reference using latitude and longitude.
15.What is QTM?
The quaternary triangular mesh refrenshing system tries to deal with irregularities in the earth surface.
16.What is GIS?
Its a computer based information system primarily aims in collecting, classifying, crosschecking, manipulating, interpreting, retrieving and displaying data which are spatially referred to the earth in an appealing way.
17.What are the components of GIS?
i) The Computer System (Hardware and Operating System)
ii) The Software
iii) Spatial Data
iv) Data Management and analysis procedures
v) The People to operate the GIS
18.What are the GIS softwares used? Standard GIS Softwares