This document discusses geo-referencing and geo-coding. Geo-referencing is the process of aligning raster images and vector data to real-world coordinates so they can be overlaid and analyzed with other geographic data in a GIS. There are two main types: geo-referencing raster images and geo-referencing vector data. Geo-coding involves assigning coordinates to point data, often by matching addresses. While geo-referencing aligns geographic images, geo-coding specifically matches addresses to latitude and longitude coordinates.

1. Geo-Referencing & Geo-Coding

2. Contents
 Geo-referencing
 Need for Geo-referencing
 Types of Geo-referencing
 Methods
 Steps for Geo-referencing
 Geo-coding
 Difference between the two
 Geo-referencing for digitization

3. Geo-Referencing
 Geo-referencing is the process of scaling, rotating, translating and
de-skewing the image to match a particular size and position
To Georeference means to associate something with locations
in physical space.
The term is commonly used in the geographic information
systems field to describe the process of associating a physical
map or raster image of a map with spatial locations
 Georeferencing may be applied to any kind of object or
structure that can be related to a geographical location, such as
points of interest, roads, places, bridges, or buildings

4. Need for Geo-referencing
Geo-reference is used when establishing the relation between raster
or vector images by determining the spatial location of the
geographical features
This procedure is mandatory for data modeling in the field of
geographic information systems (GIS)
When data from different sources or time periods (like time series
satellite images) need to be combined and then used in a GIS
application, (e.g. for change detection, assess damages after a
natural disaster etc.), it becomes essential to have a common
referencing system

5. Types of Geo-referencing
Two types:
1.Geo-referencing Raster Images
2.Geo-referencing Vector Data

6. Geo-referencing Raster Images
 A crucial element of any mapping project is registering a map with the correct
real world coordinates. This procedure is called geo-referencing. If the maps
are not geo-referenced, no other information can be displayed over or
positioned under the map coverage.
 Depending on the source materials and the specifications of the project, maps
can be registered to either a coordinate system or to another base map such as
a digital ortho photo.

7. Geo-referencing Vector Data
Vector data can be geo-referenced (or rubber sheeted) to
real world coordinates. Vector data can be either rubber
sheeted to match existing base maps or the data may be
projected into a specific coordinate system.

8. Geo-Coding
 Geocoding is the conversion of Geo-refencing (spatial information)
into digital form
 Geocoding involves capturing the map, and sometimes also
capturing the attributes
 Assigning spatial coordinates to point data

10. Geocoding Methods for Maps
 Digitizing
 Scanning
 Field Data Collection
 Vector and Raster
In ArcView Feature Data Source, Image Data Source
 Often involves address matching

11. Difference between the two
Geo-referencing: Matching geographic images to
coordinates
Geo-coding: Matching addresses to geographic coordinates
(latitude & longitude)

12. Geo-referencing for Digitization
What is digitization?
Capturing data by converting features on a paper map or (digital) aerial
photograph into digital vector format
Methods
Method Devices
Manual digitising • Coordinate entry via keyboard
• Digitising tablet with cursor
• Mouse cursor on the computer
monitor: on screen digitising (heads-up)
• Digital photogrammetry
Automatic digitising • Scanner
Semi-automatic
digitising
• Scanner and line-following software

13. The image is a photo of the 3D model
Georeferencing: What to do?
Data are not yet structured into classified
and coded objects
Image data has to be vectorised and structured first

14. Conclusion
Used to convert the entire map onto a real-world co-ordinate system
With Georeferencing you can align geographic data to a known coordinate
system so it can be viewed, queried, and analyzed with other geographic data
Geocoding is a GIS operation for converting street addresses into spatial data
that can be displayed as features on a map, usually by referencing address
information from a street segment data layer