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Introduction
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GIS & Remote Sensing

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GIS
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A GIS is a computer-based system to aid in the collection, maintenance, storage,
analysis, output, and distribution of spatial data and information.
Two important components - What, and Where
GIS software have evolved to robust (sort of) tools capable of a wide variety of
tasks :
ESRI (ArcGIS) Microimages ERDAS GRASS
Quantum GIS (QGIS) Autocad MapInfo Idrisi
Manifold Intergraph

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A GIS is composed of hardware, soft- ware, data, humans, and a set of
organizational protocols.

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5.
Data Models
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CE 454
GIS & Remote Sensing

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Data Model: Define spatial objects in a database, And represent relationships
among objects (connection, adjacency, proximity, influence)

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Dr. Duaij AlRukaibi

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REPRESENTATION AND DATA STRUCTURES
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Terms
Entities - "things" in the real world we
represent (Rivers, buildings, soil types,
wetlands)
Objects - our representation in a data model

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REPRESENTATION AND DATA STRUCTURES
COORDINATES AND ATTRIBUTES
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• Most common
data models
define thematic
layers
• typically, layers,
one layer for
each distinct
view of a theme

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CARTESIAN COORDINATES
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• Coordinates define location in two or three dimensional space.
• Coordinate (X,Y,Z) used to define the shape and location of each spatial object.
Dr. Duaij AlRukaibi

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• It is Angular measurement on sphere.
• Uses 2 angles of rotations and a radius distance to
specify location on a modeled earth surface.
• The first angle (longitude):
• is measured around imaginary axes which earth spins.
• Zero is set for a location in England and angle is
positive eastward and negative westward.
• Zero longitude Known as Prime Meridian or Greenwich
Meridian.
• The second angle (latitude):
• Measured along lines that intersect both north and south
poles. Set zero at equator.
• Lines of constant longitude called Meridian
• Lines of constant latitude called Parallels
• Calculation of longitude and Latitude:
1. Leading Letter (N,S,E,W) with number (example
N90O, S10O
2. Signed Coordinates (-90,+90, +71, -62).
• Spherical Coordinates are recorded in degree, minutes,
second (DMS) or Decimal Degree (DD).
• Each degree made of 60 minutes of arc
• Each minutes is in turn divided to 60 seconds of arc (3600).

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COMMON DATA MODELS
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MANY OBJECTS FOR A THEME,
WITH PROPERTIES RECORDED
FOR EACH OBJECT
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Attribute data (Item or Variable ) are used
to record the non-spatial characteristics of
an entity.
It describe the feature in color, depth,
weight, owner, land use, etc.
Attributes presented in a table which in
each row corresponds to spatial object
and each column corresponds to an
attribute.

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COMMON DATA MODELS
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VECTOR DATA MODELS
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• A vector data model uses sets of coordinates and association attributes table to define discrete
objects.
• There are 3 basic types of vector objects: Points, Lines, and Polygons
1. Point: uses a single coordinate pair to represent the location of an entity (Gas wells, Light
Poles, Accident Location and Survey points. Attribute data attached to each point to represent
non-spatial characteristics.
2. Lines: represent as an ordered set of coordinate pairs.
3. Polygon: formed by a set of connected lines

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VECTORS DEFINE DISCRETE FEATURES
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VECTOR TOPOLOGY
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• A vector topology is struct connectivity and recording adjacency. Types of Topology are:
1. Spaghetti: lines may not intersect when they should, and may overlap without connecting
2. Topological: create an intersection and place a node at each line crossing. Record connectivity
and adjacency.
1. Planner topology: No overlaps among lines or polygons in same layer.
2. Non-planner topology: exists overlaps among lines or polygons in same layer.
3. Topological-warped: create an intersection and place a node at each crossing with curve lines.

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RASTER DATA MODELS
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• A vector data model uses sets of coordinates and association attributes table to define discrete
objects.
• There are 3 basic types of vector objects: Points, Lines, and Polygons
1. Point: uses a single coordinate pair to represent the location of an entity (Gas wells, Light
Poles, Accident Location and Survey points. Attribute data attached to each point to represent
non-spatial characteristics.
2. Lines: represent as an ordered set of coordinate pairs.
3. Polygon: formed by a set of connected lines