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After some googling around both seem to be interchangable words, where we speak of tying the spatial info of a real place and storing in database.

But still I am not satisfied, there should be some major differences. Also are there any tools in Oracle Spatial suite for this to carry out.

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4 Answers 4

up vote 7 down vote accepted

To easily understand these terms, let's use example of an online mapping service (say Google maps, Mapquest etc.)

  • When you type an address or a placename in the searchbox and in return the map shows a marker at the place. The process of associating an address or a placename with coordinates on the map is called Geocoding. In a spatial database this is done as a point layer with name of the place as an attribute to the point location. This is one way of geocoding. For addresses, the associated coordinates are not saved in a database directly, but computed using a method called linear referencing. (Thus the confusion between the terms geo-referencing and linear-referencing ) The start and end addresses along a line segment are saved and intermediate addresses are interpolated and the coordinates are calculated. As for your question, Oracle spatial has linear referencing support. http://docs.oracle.com/html/A88805_01/sdo_lrsa.htm

  • In some online mapping service, you may have seen satellite imagery. When these images are captured from a satellite or an airplane, they are just plain images, like photographs. But to display these images on a map, they need to be associated with map coordinates. This process is called GeoReferencing. Once the image is associated with the map coordinates it can be overlaid on top of street maps. For georeferencing, you can use a GIS software such as ArcGIS or QGIS to georeference an otherwise un-referenced image or scanned maps, and load them into Oracle Spatial.

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You can certainly have address points stored in the database, which are considered more accurate (especially important for emergency services routing). –  blah238 Jul 1 '12 at 14:48

I use the term "georeferencing" when I am referring to applying geographic information to data. Such as "georeferencing an image" so it will align with the rest of my data. I'll use "geocoding" when I have address/post code information and I want to georeference them.

Geocoding on Wikipedia

Georeferencing on Wikipedia

But you probably read those anyway.

Maybe someone else can speak about the tools in Oracle Spatial.

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You actually described reverse geocoding (assigning address/postcodes to spatial data). –  blah238 Jul 1 '12 at 1:32
Thanks, you're right. I actually gave a demonstration to people at work for geocoding addresses using Google Fusion. I got mixed up somehow. I've edited my post to reflect the correct definition. –  Fezter Jul 2 '12 at 9:52

I see them as separate activities.

Geocoding is the process of taking coded location information (such as addresses or grids) and turning it into explicit location information (X and Y coordinates, usually). Reverse geocoding is the opposite, taking XY data and locating the nearest address, grid, etc.

Georeferencing is the process of taking a raster image or vector coverage, assigning it a coordinate system and coordinates, and translating, transforming, and warping/rubbersheeting it into position relative to some other spatial data, such as survey locations, street intersections, etc.

This can be sometimes also be called rectification or georectification interchangeably, while in some contexts, georeferencing is considered to only include the assigning of a spatial reference and coordinates to the image, and rectification is the transformation and resampling of the image to remove distortion (as in orthorectification).

In ArcGIS, georeferencing is transitory (on-the-fly transformation of the source image) while rectification is permanent (creating a new resampled image given a georeferenced raster layer).

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My abbreviated take:

Georeferencing involves fitting an image to the Earth based on matching up visual features of the image with their known location.

  • Input: Imagery, Image control points, Matching geospatial control points
  • Output: Image with data attached showing how it fits onto the globe

Geocoding involves converting some human placename or label into coordinates. Often this is done thousands of items at a time.

  • Input: "642 Arbitrary Lane, Cityville, MA" or "Miami" or "FIPS county #64623", large database of spatial reference info
  • Output: "53.645 N, 73.6453 W"
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You can also georeference a vector. Perhaps you have imported CAD data that represents a utility network (but contains no spatial reference) to vector format. If you were to rubbersheet that vector to a basemap, probably imagery or an image that has been scanned and georef'd, then you would have georef'd the vector. –  user3461 Jul 1 '12 at 12:00

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