Height estimation methods for filling gaps in gridded DTM

Digital terrain models (DTMs) describing the relief of the terrain constitu te a central component of mapping and geographic information systems, in ge neral, and photogrammetric mapping, in particular. In practice, the limitat ions of photogrammetric measurement methods for collecting the relief infor mation cause discontinuities and gaps in the database. The possibility of a utomatically completing and correcting the missing information by calculati on, without requiring additional measuring, offers an inexpensive, rapid, a nd attractive alternative. This paper presents an analysis based on practic al experiments of the capabilities and limitations of various methods of fi lling the gaps in gridded relief databases. Also presented are effects of d ifferent relief types and grids of varying densities on the accuracy obtain ed in automatically filling the gaps in gridded DTM databases. The recommen ded estimation method is based on a weighted average of 1D third-order poly nomials assembled around the required point in two prime directions. The pr oposed method is much faster than other common methods such as 2D polynomia ls, kriging, etc., yet it is just as accurate. This method can therefore be employed in the course of using various applications, in real time, with n o need for editing and preliminary changes of the relief data in the databa se.