DATA INPUTS METHODS IN GIS

 

METHODS OF DATA INPUTS:-

Data input is the method of encoding data in computer readable form and capture the data in GIS database. Data entry is usually the main hurdle in applying GIS. The initial cost of creating a database is usually higher. Generally two types of data entered into the GIS systems. One is spatial data and another is spatial data.

Four types of data entry methods are commonly used in GIS. These are –

1. Keyboard entry.

2. Manual digitizing.

3. Automatic digitizing.

4. Conversion of digital data files.

 

1. KEYBOARD ENTRY: - This method is also known as keyboard encoding method. Most of the case attribute data is usually input by keyboard but spatial data is rarely input by keyboard. Both spatial and attribute data is inserted into GIS system using the keyboard terminal of the computer.

Advantages:    i) very easy to use.

                        ii) Both spatial and attribute data can input.

                        iii) Most precise and accurate technique compared to others.

Disadvantages: i) This method becomes difficult to perform when number of entries is huge.

                         ii) This method is rarely used for storing spatial data.

 

2. MANUAL DIGITIZING: - This is one of the most common and widely used spatial data input techniques from maps in GIS. A digital base map is collected which is georeferenced using GIS software. After completing the georeferenced process, all features of the map is digitized using a computer mouse, this method is called on-screen digitizing. In this method digitizer uses a puck (mouse-like tool) or cursor to trace point, line and polygon of a hard copy map, this method also known as hard copy digitizing. The purpose of digitization is to nourish the coordinates in the computer.

 

Advantages: i) Ability to copy the map correctly in poor conditions.

                     ii) It has the ability to easily register and update existing data.

Disadvantages: i) Computers are at greater risk of errors when interpreting poor quality     images or information on maps.

                              ii) Digitization accuracy depends on the efficiency of the digitizer.

3. AUTOMATIC DIGITIZING: - variety of scanning devices exists for the automatic digitizing. In this method, a digital image of the map is produced by moving an electronic detector across the surface of the map. This is the faster way of data entry in GIS compared to other process. Two types of scanners mainly used in this process, one is Drum scanner and another is Flat-bed scanner.

Advantages:-i)Fastest data entry method.

                      ii)Reduces data entry time.

Disadvantages:-i)It is an expensive technique because scanners are very costly.

                          ii) scanned data requires some amount of manual editing to create a clean data layer.

4. CONVERSION OF DIGITAL DATA FILES: - Over the last few years this process has become popular for data input. There are many government organizations and private companies on the market that preparing and sell digital data files often in a format that can be read directly into a GIS.

                       

                             Some data entry method described above. The choice of specific data input technology depends on various factors such as how data is collected, what accuracy is required in the output, resources and available time, project cost, etc.

               

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