Updating of vague geographic objects in topographic databases of NMCAs – case Finland

Abstract. The identification and delineation of geographic objects, a fundamental yet subjective aspect of topographic mapping, forms the basis for creating abstract models of our surrounding physical environment and has captivated researchers due to its complexity and conceptual challenges. Although topographic maps and databases of the National Mapping and Cadastral Agencies (NMCAs) often represent objects with sharp boundaries, this is usually the result of practical reasons and user needs for modelling the data, rather than our know knowledge of inherent vagueness of many geographic objects and the associated cognitive processes involved in their recognition. The main objective of this article is to increase our understanding of the role of vague geographic objects as part of the topographic data production of NMCAs and to develop a generic TDB Change Detection tool to help the analysis of changed features in topographic databases (TDBs). The experimental part of this work is focused on the TDB versions produced by the National Land Survey of Finland (NLS) in 2021–2024 and it provides answers to (a) what kind and how many changes are made to the vague features in the NLS TDB within the observation period, and (b) how are the changes distributed by feature class and region. The selected vague feature classes were outcrops of bedrock, cliffs, young and other bogs, lakes and ponds, and contours. Buildings were used as a reference when analysing the total number of changes over the whole of Finland. The results show that the number of changes made for analysed feature classes was much higher than expected. The largest number of changes occurred in bogs, outcrops and contours. In general, the largest amount of modified features appeared to be concentrated in southern Finland and in the northernmost parts of Finland. The spatial variation in changes is explained both by the spatial variation in topography and by the individual characteristics of different topographers operating in different parts of Finland. Based on the results, the work made it possible to make a number of recommendations to 1) improve the understanding of the nature and significance of topographic interpreted data within NMCAs, 2) clarify NMCAs own position on the quality requirements for the geometry and timeliness of vague topographic features, 3) develop precise guidelines and guidance for the data collection process, 4) to develop tools to monitor the topographic data collection work done, and 5) for NMCAs to regularly archive frozen versions of their TDBs to enable efficient monitoring of data production process afterwards.