Lec_3_Intro to Digitizing
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The document discusses digitizing, which is the process of converting analog geographic data into digital vector data. There are two main types of digitizing - automatic digitizing which uses image processing to convert raster to vector, and manual digitizing. Manual digitizing can be done on a tablet by tracing a hard copy, or on a computer screen using a mouse or digitizing cursor. When digitizing on screen, there are two modes: point mode places vertices manually and is slower but more accurate, while stream mode automatically places vertices and is faster but produces heavier files.
Lec_3_Intro to Digitizing
- 1. Introduction to Digitizing Prof. Dr. Sajid Rashid Ahmad sajidpu@yahoo.com Atiqa Ijaz Khan _ Demonstrator atiqa_ss09@yahoo.com
- 2. Digitizing • “The process of converting features on a map into a digital format.” • “The process of converting analog information into a digital format.” • The process of creating a single point feature with an x,y coordinate. • The process of converting geographic data either from a hardcopy or a scanned image into vector data by tracing the features • The x,y coordinates of features are automatically recorded and stored as spatial data. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 2
- 3. Types of Digitizing Institute of Geology, University of the Punjab Tuesday, November 11, 2014 3
- 4. Automatic Digitizing • An automatic process to convert a raster into a vector. • Mostly using image processing and pattern recognition techniques. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 4
- 5. Manual Digitizing • Manual digitizing method involves two types: Institute of Geology, University of the Punjab Tuesday, November 11, 2014 5
- 6. • On Tablet: • Done by Digitizer. • Operator manually traces all lines from a hard copy or scanned map. • But, it is more time consuming. • And level of accuracy is not very good. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 6
- 7. • On Screen: • Simplest way to create the vectors. • From computer screen using a mouse of digitizing cursor. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 7
- 8. • Point Mode Digitizing: • Vertices are placed by hand at desired interval. • It is a slower process. • But less redundancy (repetition). • And more accurate. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 8
- 9. • Stream Mode Digitizing: • Half automatic process. • Software insert vertices every time when a particular distance or time threshold pass out. • Faster process. • But, produce large and heavy files, with redundant information. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 9
- 10. Institute of Geology, University of the Punjab Tuesday, November 11, 2014 10