| 1. |
- Granholm, Ann-Helen, et al.
(författare)
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The potential of digital surface models based on aerial images for automated vegetation mapping
- 2015
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Ingår i: International Journal of Remote Sensing. - : Informa UK Limited. - 0143-1161 .- 1366-5901. ; 36, s. 1855-1870
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Tidskriftsartikel (refereegranskat)abstract
- Segmentation of vegetation patches was tested using canopy height models (CHMs) representing the height difference between digital surface models (DSMs), generated by matching digital aerial images from the Z/I Digital Mapping Camera, and a digital elevation model (DEM) based on airborne laser scanner data. Three different combinations of aerial images were used in the production of the CHMs to test the effect of flight altitude and stereo overlap on segmentation accuracy. Segmentation results were evaluated using the standard deviation of photo-interpreted tree height within segments, as well as by visual comparison to existing maps. In addition, height percentiles extracted from the CHMs were used to estimate tree heights. Tree height estimation at the segment level yielded root mean square error (RMSE) values of 2.0 m, or 15.1%, and an adjusted coefficient of determination (adjusted R2) of 0.94 when using a CHM from images acquired at an altitude of 1200 m above ground level (agl) and with an along-track stereo overlap of 80%. When a CHM based on images acquired at 4800 m agl and an overlap of 60% was used, the corresponding results were an RMSE of 2.2 m, or 16.0%, and an adjusted R2 of 0.92. Tree height estimation at the plot level was most accurate for densely forested plots dominated by coniferous tree species (RMSE of 2.1 m, or 9.8%, and adjusted R2 of 0.88). It is shown that CHMs based on aerial images acquired at 4800 m agl and with 60% along-track stereo overlap are useful for the segmentation of vegetation and are at least as good as those based on aerial images collected at a lower flight altitude or with greater overlap.
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| 2. |
- Holmgren, Helen, 1970, et al.
(författare)
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Variation Theory as Teaching Method in Introductory Accounting Courses - Effects on Student Learning
- 2017
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Ingår i: 40th Annual Congress of the European Accounting Association 2017. 10-12 May 2017, Valencia, Spain..
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Konferensbidrag (refereegranskat)abstract
- In this paper we study effects on student learning from a systematic use of variation theory in the structure of lectures. We study three introductory financial accounting courses in the 2015-16 academic year. Students are randomly assigned to groups, where the treatment group is exposed to a lecture based on variation theory, and the control group is exposed to a traditional lecture. We measure student understanding both before and after the course, using both essay questions and multiple choice questions. The understanding that we focus on is the link between balance sheet measurement and net income, and the relation to stakeholder incentives and interests. We hypothesize and find that students in the treatment group have a better understanding of financial accounting. We also note that essay questions are more effective than multiple choice questions in measuring understanding. In addition, it may be important to consider pre-study experience of accounting (e.g. through work experience), as this has a substantial impact on the level of understanding.
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