Aerial mapping refers to the creation of planimetric maps, including contours and features taken from aerotriangulated aerial imagery. One concept and practice commonly involved in the creation of high quality maps is orthomosaic mapping. 

 

Orthomosaic Mapping Explained

 

Orthomosaic Aerial mapping consists of two processes - orthorectification and mosaicking. In orthorectification imagery is corrected for distortion with the application of elevation and camera model information so that the scale variation corresponds to a projection on the map in the whole image. The process of imagery correction (removal of distortion) using camera model and elevation data, such that the scale variation is consistent with a map projection in the whole image, is known as orthorectification. Image distortion can be caused by a lot of factors, such as the lens used, collection geometry and feature and terrain elevation. In mosaicking, a number of images are sewn together to make a single image. In summary, orthomosaicking requires the combination of these two processes, where a number images will be merged into a single image, and the resulting distortions are eliminated.

 

A Closer Look at Orthorectification

 

When a sensor captures an image, especially in oblique (non-vertical) collection geometry, the collected output usually comes with inherent distortion. Normally, this happens when the imaged area is mountainous or hilly. Distortions are always part of the deal. One type of distortion is known as layover, which is caused by the higher elevation being closely located to the sensor. Sometimes, layover is also produced when there are significant shifts in the location of a feature. Without orthorectification, layover will continue and GIS (geographical information system) layers, or those geographic datasets in a digital map environment, do not line up.

 

Mosaicking - A Closer Look

 

There are several growing fields of interest in significant areas around the world, specifically in the analysis of communication, power and transportation infrastructure. These infrastructure networks cater to huge portions of entire nations. The creation of mosaics with the use of these networks use up hundreds of gigabytes of image data. Related articles pertaining to this are provided in the site at http://www.ehow.com/info_8621214_difference-satellite-imagery-aerial-photography.html. Analysts will not wait too long for a tool to create a mosaic prior to analysis. Several gigabytes will be consumed, even in modest areas of interest (for example, cities or towns).

 

Orthomosaic Mapping

 

Users these usually have a need for monitoring wide areas and do Engineering survey and take other georeferenced data, like GIS layers, into their analytical field. Many users are not professionals in photogrammetry or pixel manipulation. Their skills are chiefly focused on the analysis of features and their timelines, as well as on making timely and correct conclusions. Because areas of interest often include many images, analysts have a need for tools that stitch all these images together in a fast and convenient manner, en route to constructing the broad area coverage. They should also have tools that take the work out of installing GIS layers in right positions on the wide area images. Layer alignment is always crucial when it comes to generating accurate conclusions.