An Evaluation of Alternative Methods of Soil Mapping

Soil surveys have been conducted in Alberta for the past 70 years. Over the last 15 years the majority of soils information has been compiled at Survey Intensity Level 3 (SIL3) 1:50,000 map scale. Production of these maps is costly and requires large numbers of personnel. The Federal and Provincial governments are no longer prepared to financially support soil inventory at this level. This project was conducted to evaluate and compare alternative soil mapping methods (top-down and landscape mapping) in comparison to traditional SIL3 1:50,000 soil maps. Six townships were mapped and compiled at 1:50,000 and evaluated on the basis of cartometrics, map accuracy and time required to conduct mapping.

Cartometric analysis showed that the average sized polygon occupied 124 ha on SIL3 1:50,000 maps, 166 ha on landscape maps and approximately 190 ha on the top-down maps. Consequently, the soil maps produced by alternative methods had fewer polygons delineated per township than the SIL3 1:50,000 maps.

Map accuracy was defined as the degree of correspondence between the soils predicted by a map legend to occur at a given site and the soils found in the field. Results of the study show that top-down and landscape mapping methods had map accuracies similar to SIL3 1:50,000 maps. Map accuracies between methods were not statistically significantly different at the 95% confidence level. The landscape mapping method provided the highest map accuracy, followed by top-down and SIL3 1:50 000 mapping methods. Map accuracies of the various mapping methods were similar regardless of the amount of time spent in the field or the number of observations.

Analysis of the results leads to the conclusion that both the top-down and landscape mapping methods are viable alternatives to SIL3 1:50,000 mapping and should be employed in future soil mapping projects.