subject: Two Methods for Planimetric Feature Extraction [print this page] Two Methods for Planimetric Feature Extraction
Planimetric features are the features that explain the irregularities on a plane. To capture the features perfectly there are two types of methods employed, namely monoscopic and stereoscopic. In monoscopic method it is generally 2D feature extraction, while in stereoscopic method it is 3 D feature extraction. Both these methods have found applications in wide number of industries. Today's map makers and cartographers depend on these methods to build their maps with topographic and cartographic features.
Monoscopic Method composes of comparison of various radiometric and geometric data with their impact on resulting images received from panchromatic SPOT and airborne SAR. In Monoscopic Processing, the result will be a map with representation in XY co-ordinates alone. It has generally three processes for creating a Cartographic map. They are
Merging of Image and Digital Elevation Model (DEM)
In this method, Digital Elevation Model or DEM is generated through processes such as interferometry, stereoscopy, contour lines digitizing, etc. The output of DEM will acquire some errors. These errors will be carried over to the subsequent processes in Monoscopic Processing. In addition, the process of re-sampling in rectification will result in obscure radiometric and geometric features and thereby interpretability of the images.
In stereoscopic method, the 2D images of the objects are compared and merged to create a 3D virtual stereo-model. This stereo model is then used to create 3D maps with planimetric and altimetric features. The features are extracted and expressed in 3D, i.e., in XYZ cartographic co-ordinates. Stereoscopic processing is a five-step processing.
