2. TECHNIQUES
• Key Encoding
• Digitizing
– Heads down digitizing
– Heads up digitizing
• Scanning
• Coordinate Geometry Method
• Direct File transfer
3. Key Encoding
• keyboard entry method.
• Data is inserted into GIS using the keyboard terminal of the
computer.
• It is possible to enter both spatial (such as coordinates of
locations etc.,) and non-spatial data using this method.
• store attribute data.
• When number of entries becomes huge, this method
becomes difficult to perform.
• Most precise and accurate compared to other methods as
details entered directly by the user, and no changes (from
what are observed in the field or log book) are expected to
reflect in the map.
4. Digitizing (Manual)
• A variety of hardware is deployed in this method depending
on method of digitizing.
Following are 2 different types of digitizing techniques.
• HEADS DOWN DIGITIZING:
• In this method equipment such as a digitizing table, a hand
held tracing device (such as digitizing pen or marker),
computer etc., are used in the process of digitizing.
• Digitizing table consists of a fine wire mesh, the positions
of which are controlled and calculated in GIS frame work
attached to it.
• This entire process is called heads down digitizing as the
operator keeps his head down during entire process.
5. Digitizing
• Heads up digitizing:
• Here, a digital base map is collected and is geo
referenced using GIS software. Then all features
in the map are digitized using the computer
mouse, while looking at the geometry of objects
on computer screen.
• In this process, operator keeps his head up, and
hence called as heads up digitization.
• Digitization results in shape files, which are vector
features.
6. Scanning (Automated)
• Scanning is much faster way inputting data into GIS.
• Scanners makes use of an electronic detector for
encoding the data into GIS.
TYPES OF SCANNERS
Laser scanner
Flat bed scanner
Rotating drum scanner
• However, data cleaning or editing process may be
needed for such results generated from the scanning as
some discrepancies may exist in it.
7. Coordinate Geometry Method
• This technique is also called as COGO method.
• The survey measurements such as bearings and
lengths are taken as input and entered into GIS
using keyboard.
• Coordinates of objects and features are
calculated by the GIS.
• This input technique produces highly accurate
results and is useful in preparing cadastral maps.
• It takes lot of time, manpower and cost to
produce the maps compared with normal
digitizing process.
8. Direct File transfer
• There are many public and private sources for collecting
GIS data.
• At present many organizations are preparing and selling GIS
data sets.
• If any such data is available, it is possible to collect and
transfer the files directly into GIS after making adjustments
as per the current application.
• Other than this, the satellite imagery acquired from space
and digital aerial photographs are also compatible with
GIS to be readily processed.
• Depends on several factors such as how the data is
collected, what precision is required in the output,
resources and time available, cost of project etc.
