What do you mean by
Georeferencing?
Definition: Georeferencing is the process of imposing real world
geographic (XY) coordinates to each pixel of a raster image.When the
co-ordinate of the features of the scanned maps and aerial photographs are referenced
to their relative locations on the surface of earth then it is called
georeferencing.
According to USGS, “Georeferencing
means that the internal coordinate system of a digital map or aerial
photo can be related to a ground system of geographic coordinates. A
georeferenced digital map or image has been tied to a known Earth coordinate
system, so users can determine where every point on the map or aerial photo
is located on the Earth's surface”.
What do you mean by
re-projection in GIS?
Projections are a
mathematical transformation process that transform spherical coordinate (latitude
and longitude) to a 2D (XY) coordinate system. Based on the structure of the
earth’s surface you can say that projection is the mathematical coordinate
transformations that convert the curved surface to a flat surface.
The term re-projection
means to change the coordinate values of a dataset from one coordinate system
to another coordinate system. Mainly projection converted from spherical
coordinates to XY coordinates systems and XY coordinates to spherical
coordinates systems.
What
is Topology?
Definition:
The term ‘topology’ expresses the relationships between connected or adjacent
vector properties (points, lines and polygons) in GIS.
According to esri,” Today,
topology in GIS is generally defined as
the spatial relationships between adjacent or neighboring features”.
Applications
of Topology in GIS:-
1. Topology applied to
create quality GIS datasets.
2. Topology helps to
edit features shared between different spatial layers.
3. Topology is
necessary for network analysis.
4. The topology is
useful if you want to find the best route between five different cities.
Limitations
of Topology in GIS:-
1. Major limitation of
topological model is its mathematical based nature.
2. It is time consuming
and costly.
3. For new users
topology rules are complex.
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