When you type an address or a place name in the search box and in return the map shows a marker at the place. The process of associating an address or a place name 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.
Geo-referencing 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.
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.
Here are some of the general differences between Geo-Coding and Geo-Referencing
|– Geo-coding allows you to transform any description of location into an actual location on earth’s surface.||– Georeferencing, on the other hand, will align different types of geographic information to a known geographic coordinate system.|
|– These descriptions of locations could take form of lists of coordinates addresses, names of places or lists of named objects/services/buildings without address (only names).||– This allows a view of the respective information together with another already georeferenced layers of information.|
|– The result of this operation is a geographic feature (layer) with all additional information as an attribute table in this layer||– The process includes data shifting, scaling, rotating, rectifying, etc.|