Question

Discuss raster and vector data formats. Give example.

Answer 1

1. Raster Data Format

Raster data format represents a graphic feature as a pattern of grids of squares.

The Raster file formats are most often used for the following activities:

1. For digital representations of aerial photographs, satellite images scanned paper maps, etc.
2. When costs need to be kept down.
3. When the map does not require analysis of individual map features.
4. When backdrop maps are required.

• Advantages

1. Simple data structure
2.  Easy and efficient overlaying
3. Compatible with satellite imagery
4. High spatial variability is efficiently represented
5. Simple for own programming
6. Same grid cells for several attributes

• Disadvantages

1. Inefficient use of computer storage
2. Errors in perimeter and shape

Fig. Effect of Grid Size on data in Raster Format

2. Vector Data Format

Vector data represents the object as a set of lines drawn between specific points.

The Vector files are most often used for:

1. Highly precise applications
2. When file sizes are important.
3. When individual m; features require analysis.
4. When descriptive informa­tion must be stored.

• Advantages

1. Compact data structure
2. Efficient for network analysis
3. Efficient projection trans­formation
4. Accurate map output

• Disadvantages

1. Complex data structure
2. Difficult overlay operations

Fig. The Vector Data Model is based around coordinate pairs