Application of Remote Sensing and Geographic Information Systems for Mapping and Monitoring of Glaciers Part 2 - Glacier Database Generation using ArcGIS
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| Training Manual |
About the Manual
This manual provides an introduction to Geographic Information Systems (GIS) and ArcGIS software.
The ArcGIS
platform and tools are explained so that they can be used for generating glacier database, analysis on glacier
database and preparing glacier maps. The manual is divided into three parts – first part includes the introduction of
GIS and descriptions of some of the fundamental terms used in GIS. The second part includes the hands-on exercise
on ArcGIS to make you familiar on the software and the third part includes the detail exercise for generating different
attribute of the glacier polygon with some analysis.
Read the manual carefully before doing hands-on exercises. Step by step processes are explained in bullet point
format and short introductions to the data processing steps are in normal format.
Practice data for this manual are available at this link:
http://www.icimod.org/glacierdata/glacier_training_data.zip
Introduction to Geographic Information Systems (GIS)
A geographic information system (GIS) is a system designed to capture, store, manipulate, analyse, manage,
and present all types of geographically referenced data (Figure 1.1). Although the term GIS is commonly used
to describe software packages, a true GIS includes knowledgeable staff, hardware, data, and software. GIS
technology can be used in almost any geography-related discipline, from landscape, architecture, natural resource
management to transportation routing. The main purpose of a GIS is to turn geographic data into useful information
that can provide answers to real life questions.
Geographic – The key word is ‘geography’, which means that the data and information are associated with some
location in space or referenced to locations on the earth.
Information – Tabular; attributes, or characteristics (data) can be used to symbolize and provide further insight into a
given location.
Systems – a seamless operation linking the information to the geography – which requires hardware, networks,
software, data, and operational procedures.
Functions of GIS
GIS uses the spatial and non-spatial attribute data to answer questions about the real world. Its spatial analysis
function distinguishes it from other applications. Different authors or different GIS programmers may classify functions,
manipulations, analyses and ways of data management in very different ways; in general the functions of GIS can
be grouped into four processes: data acquisition and preprocessing; database management and retrieval; spatial
modeling, measurement and analysis; and graphical output and visualization
Data Acquisition and Preprocessing
Data used in GIS often come from different sources, are of many types, and are stored in different ways. A GIS
provides tools and a method for integrating different data into a format to be compared and analysed. Data
sources range from manual digitization and scanning of aerial photographs to paper maps and existing digital data
sets. Remote-sensing satellite imagery and GPS are promising data input sources for GIS. It also provides a huge
opportunity to interactively experiment with available data in order to obtain requisite map output or to confidently
allow for any subsequent data analysis.
Database Management, Update and Retrieval
After data are collected and integrated, the GIS must provide facilities that can store and maintain data. Effective
data management can be defined in many ways but should include all of the following aspects: data storage, data
retrieval, data maintenance, data security and data integrity.
Spatial Modeling, Measurement and Analysis
Once data is acquired, assessed and stored, the collected information will be analysed and interpreted quantitatively
and qualitatively. For example, satellite imagery can assist an agricultural scientist to project crop yield per hectare
for a particular region. For the same region, the scientist also has the rainfall data for the past six months collected
through weather station observations. The scientist also has a map of the soils in the region that shows the level of
fertility and suitability for agriculture. These point data can be interpolated to get a thematic map showing isohyets,
which are contour lines of rainfall. It can integrate various data sources and generate the final map which can help
for decision makers. Some of the examples are – suitability map for settlement, agriculture and landslide susceptibility
etc.
Presenting Results – Graphical Output and Visualization
One of the most exciting aspects of GIS technology is the variety of ways in which the information can be presented
once it has been processed by GIS. Traditional methods of tabulating and graphing data can be supplemented by
maps and three-dimensional images. Visual communication is one of the most fascinating aspects of GIS technology
and is available in a diverse range of output options.
1.2 Fundamental Data Types Used in
Spatial data in a GIS database are stored in either vector or raster format.
Raster Data
Rater data generalizes map features as cells or pixels in a grid matrix. The space is defined by a matrix of points
or cells organized into rows and columns. In a raster data set, data values for a given parameter are stored in
each cell – these values may represent an elevation in metres above sea level, a land use class, a plant biomass in
grams per square meter, and so forth. The spatial resolution of the raster data set is determined by the size of the
cell
Vector Data
In vector data, objects are represented as points, lines or areas, whose positions are precisely specified. The
position of each object is defined by a (series of) coordinate pairs. A point is described by a single X-Y coordinate
pair and by its name or label. A line is described by a set of coordinate pairs and by its name and label.
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