INTEGRATING PROPERTIES OF SOIL MAP DELINEATIONS INTO ORDINARY KRIGING

Stratification of a region based on soil map delineations followed by within-stratum interpolation is sometimes used to combine soil maps an d spatial interpolation. However, not all delineations are equally sui table to subdivide an area into precisely located mutually exclusive s trata. This paper proposes a flow-path to characterize the nature of s oil map delineations and a methodology to integrate the properties of map delineations into ordinary kriging. Four types of delineations wer e distinguished based on three criteria: the nature of transition (dis continuous or gradual), the mapping accuracy, and the structure of the within-unit spatial variation. For each type of delineation the ordin ary kriging algorithm was modified to integrate its properties in the interpolation. As a test case, the sand content of the topsoil in the province of West-Flanders (Belgium) was mapped, using independent test data for validation. Inside the mapping units and at delineations ide ntified as gradual transitions, our procedure, termed ordinary kriging integrating properties of map delineations (OKPD), performed similarl y to stratified ordinary kriging (SOK). However, close to the delineat ions identified as inaccurately mapped discontinuities the mean square prediction error of OKPD was 0.64 times that of SOK. Moreover, near t hese delineations, the prediction variance was largely underestimated by SOK (relative variance = 5.1), whereas OKPD produced a more realist ic value (relative variance = 1.5).