What is it about?
The authors undertook to examine and analyse the changes in the relief in Łódź city centre over a period of over one hundred years. Archival cartographic resources containing morphometric information and contemporary laser scanning data (LIDAR) are used to analyse changes. This required appropriate transformation of these data to generate a differential relief map. Information on the geographical environment (waters, relief) is linked to the spatial development of the city. The analyses revealed several characteristic types of changes occurring in the area, which are presented in the form of case studies.
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Why is it important?
The authors pointed out the problems that can occur when trying to compare archival 100-year-old cartographic resources with contemporary laser scanning data (LIDAR). The first difficulty lies in finding and acquiring maps containing elevation data of sufficient quality. It must be kept in mind that in the case of archival data, elevation data were obtained by direct measurements in the field, while contours were interpolated and plotted manually by cartographers (using traditional tools such as French curves). In addition, such measurements required a correspondingly long time, followed by recalculations, which limited their simultaneity. The situation is completely different in the case of data obtained from automatic measurements. They are acquired at a specific time interval, made with the same standardised equipment and then processed into a numerical terrain model using the same algorithms. In the case of digital models, to recreate this former concept of plotting the terrain surface, morphometric data can be subjected to smoothing and generalisation (e.g., with tools such as the following: Smoothing functions, spline interpolation or local polynomial). After processing the numerical terrain models for the ancient and modern areas, the calculated RMSE for the 1917 map was 0.43, which was not much worse than the RMSE calculated for the LIDAR data (0.36).
Perspectives
It should be noted that the survey was conducted in only one city. The authors had good-quality archival data available. For studies of other urbanised areas, there may be difficulties in obtaining them. They are difficult to replace. The availability of modern LIDAR data is theoretically possible, but practically not every city has this type of data.
Iwona Jażdżewska
Uniwersytet Lodzki
Read the Original
This page is a summary of: Changes in Land Relief in Urbanised Areas Using Laser Scanning and Archival Data on the Example of Łódź (Poland), Remote Sensing, June 2022, MDPI AG,
DOI: 10.3390/rs14132961.
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