Data Input and Geometric transformation: Existing GIS data, Metadata, Conversion of existing data, Creating new data, Geometric transformation, RMS error and its interpretation, Resampling of pixel values.

1. GEOGRAPHICAL
INFORMATION
SYSTEM
UNIT 2
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2. use existing GIS data
 GIS data for a project is often a matter of knowledge,
experience, and luck.
 framework data, which typically include seven basic
layers
1. geodetic control (accurate positional framework for surveying and
mapping)
2. orthoimagery (rectified imagery such as orthophotos)
3. Elevation
4. Transportation
5. Hydrography
6. governmental units
7. cadastral information
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3. What is metadata
 Metadata provide information about geospatial data
 Metadata are important to anyone who plans to use
public data for a GIS project
 metadata let us know if the data meet our specific needs
for area coverage, data quality, and data currency.
 metadata show us how to transfer, process, and interpret
geospatial data.
 metadata include the contact for additional information
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4. FGDC metadata standards
categories:
 Identification information
 Data quality information
 Spatial data organization information
 Spatial reference information
 Entity and attribute information
 Distribution information
 Metadata reference information
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5. how existing data is converted
in GIS
 Public data are delivered in a variety of formats. Unless
the data format is compatible with the GIS package in
use. we must first convert the data.
 Direct Translation
 Direct translation uses a translator in a GIS package to directly
convert geospatial data from one formal to another
 Neutral Format :
 The Spatial Data Transfer Standard (SDTS) is a neutral format
approved by the Federal Information Processing Standards
(FIPS) Program in 1992
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6. SDTS uses "profiles" to
transfer spatial data
 Each profile is targeted at a particular type of spatial
data. Currently there are five SDTS profiles:
 The Topological Vector Profile (TVP) covers DLG, TIGER, and
other topology-based vector data.
 The Raster Profile and Extensions (RPE) accommodate DOQ,
DEM, and other raster data.
 The Transportation Network Profile (TNP) covers vector data with
network topology.
 The Point Profile supports geodetic control point data.
 The Computer Aided Design and Drafting Profile (CADD)
supports vector-based CADD data, with or without topology.
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7. various methods of creating
new GIS Data
 Creating New Data
 Address geocoding, also called address matching, can create point
features from street addresses. Street addresses are therefore an
important data source for creating new data.
 Remotely Sensed Data :
 Satellite images can be digitally processed to produce a wide variety of
thematic data for a GIS project.
 Field Data :
 field survey typically provides data for determining parcel boundaries
 Text Files with x-,y-Coordinates :
 Geospatial data can be generated from a text file that contains x-, y-
coordinates
Cont………..
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8.  Digitizing Using a Digitizing Table
 Digitizing is the process of converting data from analog to digital
format.
 Scanning
 A scanner converts an analog map into a scanned image file in
raster format.
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9. What is geometric transformation
 Geometric transformation is the process of using a set of
control points and transformation equations to register a
digitized map, a satellite image, or an aerial photograph
onto a projected coordinate system.
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10. Map-to-Map and Image-to-Map
transformations
 Geometric transformation converts the newly
digitized map into projected coordinates in a
process often called map-to-map
transformation.
 Image-to-map transformation applies to
remotely sensed data “satellite image into
projected coordinates”
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11. transformation methods
 proposed for transformation from one
coordinate system to another.
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12. Affine Transformation
 The affine transformation allows rotation,
translation, skew, and differential scaling on a
rectangular object, while preserving line
parallelism
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13.  A geometric transformation typically involves
three steps.
 Step 1 updates the control points to real-world
coordinates.
 Step 2 uses the control points to run an affine
transformation.
 Step 3 creates the output by applying the
transformation equations to the input features.
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14. Root Mean Square (RMS) Error
 acceptable value ranges(rms)
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15. Resampling of Pixel Values
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16. END OF UNIT 2
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