4 - Central Institute of Brackishwater Aquaculture

National Workshop-cum-Tra~ning on Biolnforrnatics and Information Management in Aquaculture
(d) Data output and presentation
(e) Interaction with the user
3.3 Data
Geographic data and related tabular data can be collected in-house or purchased
from a commercial data provider. The digital map forms the basic data input for
GIs. Tabular data related to the map objects can also be attached to the digital
data. A GIs will integrate spatial data with other data resources and can even
use a DBMS, used by most organization to maintain their data, to manage spatial
data.
3.4 People
GIs users range from technical specialists who design and maintain the system
to those who use it to help them perform their everyday work. The people who
use GIS can be broadly classified into two classes. The CADIGIS operator, whose
work is to vectorise the map objects. The use of this vectorised data to perform
query, analysis or any other work is the responsibility of a GIs engineer/user.
3.5 Method
And above all a successful GIs operates according to a well-designed plan and
business rules, which are the models and operating practices unique to each
organization. There are various techniques used for map creation and further
usage for any project. The map creation can either be automated raster to vector
creator or it can be manually vectorised using the scanned images. The source of
these digital maps can be either map prepared by any survey agency or satellite
imagery.
4. Data in GIS
A GIS stores information about the world as a collection of therned layers that
can be used together. A layer can be anything that contains similar features such
as customers, buildings, streets, lakes, or postal codes. This data contains either
an explicit geographic reference, such as a latitude and longitude coordinate, or
an implicit reference such as an address, postal code, census tract name, forest
stand identifier, or road name. There are two components: spatial data that show
where the feature is; and attribute data that provide information about the
feature. These are linked by the software. The fact that there are both spatial
and attribute data allows the database to be exploited in more ways than a
conventional database allows, as GIs provides all the functionality of the DBMS
and adds spatial functionality.
4.1 Spatial data: Spatial data is spatially referenced data that act as a model
of reality. Spatial data represent the geographical location of features for
example points, lines, area etc. Spatial data typically include various kinds of
maps, ground survey data and remotely sensed imagery and can be represented
by points, lines or polygons.
4.2 Attribute Data: Attribute data refers to various types of administrative
records, census, field sample records and collection of historical records.