scholarly journals Point-based and model-based geolocation analysis of airborne laser scanning data

2016 ◽  
Vol 56 (1) ◽  
pp. 013101 ◽  
Author(s):  
Umut Gunes Sefercik ◽  
Gurcan Buyuksalih ◽  
Karsten Jacobsen ◽  
Mehmet Alkan
2011 ◽  
Vol 41 (1) ◽  
pp. 96-107 ◽  
Author(s):  
Göran Ståhl ◽  
Sören Holm ◽  
Timothy G. Gregoire ◽  
Terje Gobakken ◽  
Erik Næsset ◽  
...  

In forest inventories, regression models are often applied to predict quantities such as biomass at the level of sampling units. In this paper, we propose a model-based inference framework for combining sampling and model errors in the variance estimation. It was applied to airborne laser (LiDAR) data sets from Hedmark County, Norway, where the model error proportion of the total variance was found to be large for both scanning (airborne laser scanning) and profiling LiDAR when biomass was estimated. With profiling LiDAR, the model error variance component for the entire county was as large as 71% whereas for airborne laser scanning, it was 43% of the total variance. Partly, this reflects the better accuracy of the pixel-based regression models estimated from scanner data as compared with the models estimated from profiler data. The framework proposed in our study can be applied in all types of sample surveys where model-based predictions are made at the level of individual sampling units. Especially, it should be useful in cases where model-assisted inference cannot be applied due to the lack of a probability sample from the target population or due to problems of correctly matching observations of auxiliary and target variables.


2020 ◽  
Vol 12 (9) ◽  
pp. 1446 ◽  
Author(s):  
Krystian Kozioł ◽  
Kamil Maciuk

The idea to verify the height of the highest peaks (summits) in the Crown of Polish Mountains arose after analyzing sources regarding the date and method of measuring the height of these mountain peaks. Our investigations revealed that this type of material is not usually available, and the first mention of height values is most often noted in the inter-war period, and occasionally before WWI (when Poland did not exist as an independent state); most of these values are still in use to this day. The problem of accurate measurement of the height of mountain peaks concerns not only the peaks analyzed by the authors, but also almost all mountain peaks worldwide. Therefore, as part of this work, several trips were organized to the highest peaks of several dozen mountain ranges in the territory of Poland. Measurement was made using a precise geodetic GNSS receiver an accuracy of within 10 cm and a DTM model based on ALS (airborne laser scanning). The results showed that commonly published heights can differ by up to several meters from the actual ones. The most important element of this work consists of the establishment of new measurements of the heights of the highest peaks of all mountain ranges in Poland, which may result in an alteration of the officially recorded heights based on this article. Apart from verification of these heights, this work also aimed to address the issue of the heights of all characteristic objects whose heights must be verified by using modern satellite techniques.


2021 ◽  
Vol 6 (1-2) ◽  
pp. 159-176
Author(s):  
Filip Prekop ◽  
Petr Krištuf

This paper presents a new hillfort site which is situated on top of „Čerťák“ Hill (651 m n. m.), Sovolusky municipality, Karlovy Vary district. It has been identified with the help of a digital terrain model based on Airborne Laser Scanning (LiDAR). Two separate lines of stone ramparts have been confirmed on top of the Čerťák Hill, formed by a significant right bank meander in the upper course of the river Střela. The inner area reaches 1.4 ha and the external enclosed area spreads to 2.3 ha. Subsequent field research yielded a collection of more than 500 pottery fragments from the Late Hallstatt period. The dispersion of finds shows relatively intensive settlement. The paper also discusses other sites in the surrounding region which date to the same period. The Hallstatt settlement seems to have been a structurally connected complex in the presented area.


2014 ◽  
Vol 44 (11) ◽  
pp. 1303-1311 ◽  
Author(s):  
Piermaria Corona ◽  
Lorenzo Fattorini ◽  
Sara Franceschi ◽  
Gianfranco Scrinzi ◽  
Chiara Torresan

Forest compartments are usually delineated according to artificial or natural boundaries and usually include portions of different strata. While volume estimation of each stratum can be performed from field plots located within each stratum, volume estimation in portions of the stratum may be problematic owing to the small number (or even the absence) of plots falling in those portions. If upper canopy heights from airborne laser scanning are available at the pixel level for the whole survey area, these data are used as auxiliary information. A ratio model presuming a proportional relationship between transformed heights (e.g., power of heights) and volumes at the pixel level is adopted to guide estimation. From this model, the volume within any portion of the survey area is estimated as the proportionality factor estimate multiplied by the total of transformed heights in that portion. This estimator is considered from the model-based, design-based, and hybrid perspectives. Variances and their estimators are derived under the three approaches together with the corresponding confidence intervals. The volume estimator and the variance estimators are checked from the design-based point of view by a simulation study performed on a real forest in northwestern Italy. An application to a public forest estate in the same zone is performed.


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