COMPARISON OF THIN PLATE SPLINE, POLYNOMIAL, C^I–FUNCTION AND SHEPARD’S INTERPOLATION TECHNIQUES WITH GPS-DERIVED DEM

 

 

 Dafer A. Algarni¹

and

Ismat M. El hassan²

 

 

ABSTRACT

The digital elevation model (DEM) is an important part of mapping and is used for several purposes including orthoimage production, image interpretation, contours derivations, and several Geographic Information System (GIS) applications. In the absence of a sophisticated digital photogrammetric system, that could provide DEM “automatically”, and absence of well distributed control points, which is usually the case in surveying, creating a DEM is not an easy task regardless of its pattern (gridded or irregular). Therefore, interpolation can be used to create the DEM from sparse points using one of the known interpolation methods. In this paper, the interpolation accuracy of some techniques, namely thin plate spline, polynomial, local C^I–Functionand weighted-distance (Shepard’s) interpolation are tested for comparison  using two Global Positioning System (GPS) derived DEMs. The results of two tests with five cases of control points, which are different in number and distribution,  show that the Shepard’s technique is most efficient with respect to accuracy as well as surface representation, followed by the spline technique. As far as accuracy, the polynomial technique seems to be equivalent to the C^I–Function technique when the number of control points are increased. However, the Polynomial technique gives better representation of the DEM surface than C^I–Function for both tests.

 

 

 

 

Published in the ITC Journal (International Journal of Applied Earth Observation and Geoinformation),  Netherlands, 2001, Vol. 3, No. 2, pp. 155-160.