scholarly journals Boat-borne radar mapping versus aerial photogrammetry and mobile laser scanning applied to river gorge monitoring

2014 ◽  
Vol 1 (1) ◽  
pp. 48-63 ◽  
Author(s):  
M. Jaud ◽  
◽  
R. Rouveure ◽  
L. Moiroux-Arvis ◽  
P. Faure ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Aerial Photogrammetry ◽  
Mapping Versus

scholarly journals Geomorphological mapping based on DEMs and GIS: A review

2019 ◽  
Vol 1 ◽  
pp. 1-1
Author(s):  
Takashi Oguchi
Keyword(s):  
Remote Sensing ◽  
Laser Scanning ◽  
Aerial Photographs ◽  
Topographic Maps ◽  
Formation Processes ◽  
Geomorphological Mapping ◽  
Topographic Data ◽  
Aerial Photogrammetry ◽  
Landform Classification ◽  
Shape Characteristics

<p><strong>Abstract.</strong> Geomorphology is a scientific discipline dealing with the characteristics, origin, and evolution of landforms. It utilizes topographic data such as spot height information, contour lines on topographic maps, and DEMs (Digital Elevation Models). Topographic data were traditionally obtained by ground surveying, but introduction of aerial photogrammetry in the early 20th century enabled more efficient data acquisition based on remote sensing. In recent years, active remote sensing methods including airborne and terrestrial laser scanning and applications of satellite radar have also been employed, and aerial photogrammetry has become easier and popular thanks to drones and a new photogrammetric method, SfM (Structure from Motion). The resultant topographic data especially raster DEMs are combined with GIS (Geographic Information Systems) to obtain derivatives such as slope and aspect as well as to conduct efficient geomorphological mapping. Resultant maps can depict various topographic characteristics based on surface height and DEM derivatives, and applications of advanced algorithms and some heuristic reasoning permit semi-automated landform classification. This quantitative approach differs from traditional and more qualitative methods to produce landform classification maps using visual interpretation of analogue aerial photographs and topographic maps as well as field observations.</p><p>For scientific purposes, landforms need to be classified based on not only shape characteristics but also formation processes and ages. Among them, DEMs only represent shape characteristics, and understanding formation processes and ages usually require other data such as properties of surficial deposits observed in the field. However, numerous geomorphological studies indicate relationships between shapes and forming-processes of landforms, and even ages of landforms affect shapes such as a wider distribution of dissected elements within older landforms. Recent introduction of artificial intelligence in geomorphology including machine learning and deep learning may permit us to better understand the relationships of shapes with processes and ages. Establishing such relationships, however, is still highly challenging, and at this moment most geomorphologists think landform classification maps based on the traditional methods are more usable than those from the DEM-based methods. Nevertheless, researchers of some other fields such as civil engineering more appreciate the DEM-based methods because they can be conducted without deep geomorphological knowledge. Therefore, the methods should be developed for interdisciplinary understanding. This paper reviews and discusses such complex situations of geomorphological mapping today in relation to historical development of methodology.</p>

scholarly journals Assessing the Orange Tree Crown Volumes Using Google Maps as a Low-Cost Photogrammetric Alternative

Agronomy ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 893 ◽  
Author(s):  
Carmen Marín-Buzón ◽  
Antonio Pérez-Romero ◽  
Fabio Tucci-Álvarez ◽  
Francisco Manzano-Agugliaro
Keyword(s):  
Laser Scanning ◽  
Low Cost ◽  
Three Dimensional ◽  
Average Error ◽  
Tree Crown ◽  
High Definition ◽  
Google Maps ◽  
Traditional Methods ◽  
Aerial Photogrammetry ◽  
Dimensional Approximation

The accurate assessment of tree crowns is important for agriculture, for example, to adjust spraying rates, to adjust irrigation rates or even to estimate biomass. Among the available methodologies, there are the traditional methods that estimate with a three-dimensional approximation figure, the HDS (High Definition Survey), or TLS (Terrestrial Laser Scanning) based on LiDAR technology, the aerial photogrammetry that has re-emerged with unmanned aerial vehicles (UAVs), as they are considered low cost. There are situations where either the cost or location does not allow for modern methods and prices such as HDS or the use of UAVs. This study proposes, as an alternative methodology, the evaluation of images extracted from Google Maps (GM) for the calculation of tree crown volume. For this purpose, measurements were taken on orange trees in the south of Spain using the four methods mentioned above to evaluate the suitability, accuracy, and limitations of GM. Using the HDS method as a reference, the photogrammetric method with UAV images has shown an average error of 10%, GM has obtained approximately 50%, while the traditional methods, in our case considering ellipsoids, have obtained 100% error. Therefore, the results with GM are encouraging and open new perspectives for the estimation of tree crown volumes at low cost compared to HDS, and without geographical flight restrictions like those of UAVs.

scholarly journals Digital Aerial Photogrammetry (DAP) and Airborne Laser Scanning (ALS) as Sources of Information about Tree Height: Comparisons of the Accuracy of Remote Sensing Methods for Tree Height Estimation

2020 ◽  
Vol 12 (11) ◽  
pp. 1808 ◽  
Author(s):  
Miłosz Mielcarek ◽  
Agnieszka Kamińska ◽  
Krzysztof Stereńczak
Keyword(s):  
Laser Scanning ◽  
Tree Height ◽  
Airborne Laser Scanning ◽  
Surface Model ◽  
Sources Of Information ◽  
Related Factors ◽  
Height Estimation ◽  
Aerial Photogrammetry ◽  
Airborne Laser ◽  
The Difference

The rapid developments in the field of digital aerial photogrammetry (DAP) in recent years have increased interest in the application of DAP data for extracting three-dimensional (3D) models of forest canopies. This technology, however, still requires further investigation to confirm its reliability in estimating forest attributes in complex forest conditions. The main purpose of this study was to evaluate the accuracy of tree height estimation based on a crown height model (CHM) generated from the difference between a DAP-derived digital surface model (DSM) and an airborne laser scanning (ALS)-derived digital terrain model (DTM). The tree heights determined based on the DAP-CHM were compared with ground-based measurements and heights obtained using ALS data only (ALS-CHM). Moreover, tree- and stand-related factors were examined to evaluate the potential influence on the obtained discrepancies between ALS- and DAP-derived heights. The obtained results indicate that the differences between the means of field-measured heights and DAP-derived heights were statistically significant. The root mean square error (RMSE) calculated in the comparison of field heights and DAP-derived heights was 1.68 m (7.34%). The results obtained for the CHM generated using only ALS data produced slightly lower errors, with RMSE = 1.25 m (5.46%) on average. Both ALS and DAP displayed the tendency to underestimate tree heights compared to those measured in the field; however, DAP produced a higher bias (1.26 m) than ALS (0.88 m). Nevertheless, DAP heights were highly correlated with the heights measured in the field (R2 = 0.95) and ALS-derived heights (R2 = 0.97). Tree species and height difference (the difference between the reference tree height and mean tree height in a sample plot) had the greatest influence on the differences between ALS- and DAP-derived heights. Our study confirms that a CHM computed based on the difference between a DAP-derived DSM and an ALS-derived DTM can be successfully used to measure the height of trees in the upper canopy layer.

scholarly journals EXPLORING THE POTENTIAL OF AERIAL PHOTOGRAMMETRY FOR 3D MODELLING OF HIGH-ALPINE ENVIRONMENTS

2016 ◽  
Vol XL-3/W4 ◽  
pp. 97-103
Author(s):  
K. Legat ◽  
K. Moe ◽  
D. Poli ◽  
E. Bollmannb
Keyword(s):  
Laser Scanning ◽  
Field Measurements ◽  
Special Focus ◽  
Digital Cameras ◽  
Textured Surfaces ◽  
Control Distribution ◽  
Aerial Photogrammetry ◽  
Technological Advances ◽  
User Groups ◽  
Alpine Environments

High-alpine areas are subject to rapid topographic changes, mainly caused by natural processes like glacial retreat and other geomorphological processes, and also due to anthropogenic interventions like construction of slopes and infrastructure in skiing resorts. Consequently, the demand for highly accurate digital terrain models (DTMs) in alpine environments has arisen. Public administrations often have dedicated resources for the regular monitoring of glaciers and natural hazard processes. In case of glaciers, traditional monitoring encompasses in-situ measurements of area and length and the estimation of volume and mass changes. Next to field measurements, data for such monitoring programs can be derived from DTMs and digital ortho photos (DOPs). Skiing resorts, on the other hand, require DTMs as input for planning and – more recently – for RTK-GNSS supported ski-slope grooming. Although different in scope, the demand of both user groups is similar: high-quality and up-to-date terrain data for extended areas often characterised by difficult accessibility and large elevation ranges. <br><br>Over the last two decades, airborne laser scanning (ALS) has replaced photogrammetric approaches as state-of-the-art technology for the acquisition of high-resolution DTMs also in alpine environments. Reasons include the higher productivity compared to (manual) stereo-photogrammetric measurements, canopy-penetration capability, and limitations of photo measurements on sparsely textured surfaces like snow or ice. Nevertheless, the last few years have shown strong technological advances in the field of aerial camera technology, image processing and photogrammetric software which led to new possibilities for image-based DTM generation even in alpine terrain. At Vermessung AVT, an Austrian-based surveying company, and its subsidiary Terra Messflug, very promising results have been achieved for various projects in high-alpine environments, using images acquired by large-format digital cameras of Microsoft’s UltraCam series and the in-house processing chain centred on the Dense-Image-Matching (DIM) software SURE by nFrames. <br><br> This paper reports the work carried out at AVT for the surface- and terrain modelling of several high-alpine areas using DIM- and ALS-based approaches. A special focus is dedicated to the influence of terrain morphology, flight planning, GNSS/IMU measurements, and ground-control distribution in the georeferencing process on the data quality. Based on the very promising results, some general recommendations for aerial photogrammetry processing in high-alpine areas are made to achieve best possible accuracy of the final 3D-, 2.5D- and 2D products.

scholarly journals Applicability Assessments of Close-Range Photogrammetry for Slope Face 3D Modelling

2020 ◽  
Vol 8 (3) ◽  
pp. 143-150
Author(s):  
Haqul Baramsyah ◽  
Less Rich
Keyword(s):  
Laser Scanning ◽  
3D Model ◽  
Laser Scanner ◽  
Cost Effective ◽  
3D Models ◽  
Digital Photogrammetry ◽  
Aerial Photogrammetry ◽  
3D Data ◽  
Image Capturing ◽  
Close Range

The digital single lens reflex (DSLR) cameras have been widely accepted to use in slope face photogrammetry rather than the expensive metric camera used for aerial photogrammetry. 3D models generated from digital photogrammetry can approach those generated from terrestrial laser scanning in term of scale and level of detail. It is cost effective and has equipment portability. This paper presents and discusses the applicability of close-range digital photogrammetry to produce 3D models of rock slope faces. Five experiments of image capturing method were conducted to capture the photographs as the input data for processing. As a consideration, the appropriate baseline lengths to capture the slope face to get better result are around 1/6 to 1/8 of target distance.  A fine quality of 3D model from data processing is obtained using strip method and convergent method with 80% overlapping in each photograph. A random camera positions with different distances from the slope face can also generate a good 3D model, however the entire target should be captured in each photograph. The accuracy of the models is generated by comparing the 3D models produced from photogrammetry with the 3D data obtained from laser scanner. The accuracy of 3D models is quite satisfactory with the mean error range from 0.008 to 0.018 m.

scholarly journals DIGITAL RECORDING AND NON-DESTRUCTIVE TECHNIQUES FOR THE UNDERSTANDING OF STRUCTURAL PERFORMANCE FOR REHABILITATING HISTORIC STRUCTURES AT THE KATHMANDU VALLEY AFTER GORKHA EARTHQUAKE 2015

2017 ◽  
Vol IV-2/W2 ◽  
pp. 243-250 ◽  
Author(s):  
S. Shrestha ◽  
M. Reina Ortiz ◽  
M. Gutland ◽  
R. Napolitano ◽  
I. M. Morris ◽  
...  
Keyword(s):  
Laser Scanning ◽  
World Heritage Site ◽  
Kathmandu Valley ◽  
Construction Technology ◽  
Gorkha Earthquake ◽  
Heritage Sites ◽  
Aerial Photogrammetry ◽  
Heritage Site ◽  
Historic Structures ◽  
Non Destructive

On 25 April 2015, the Gorkha earthquake of magnitude 7.8, severely damaged the cultural heritage sites of Nepal. In particular, the seven monument zones of the Kathmandu Valley World Heritage Site suffered extensive damage. Out of 195 surveyed monuments, 38 have completely collapsed and 157 partially damaged (DoA, 2015). In particular, the world historic city of Bhaktapur was heavily affected by the earthquake. There is, in general, a lack of knowledge regarding the traditional construction technology used in many of the most important temple monuments in Bhaktapur. To address this limitation and to assist in reconstruction and rehabilitation of the area, this study documents the existing condition of different historic structures in the Kathmandu Valley. In particular, the Nyatapola Temple is studied in detail. To record and document the condition of this temple, a combination of laser scanning and terrestrial and aerial photogrammetry are used. By also including evaluation of the temple and its supporting plinth structure using non-destructive evaluation techniques like geo-radar and micro-tremor dynamic analysis, this study will form the basis of a structural analysis study to assess the anticipated future seismic performance of the Nyatapola Temple.

scholarly journals 3D RECORDING AND MODELLING OF MIDDLE-AGE FORTRESS IN DENSE VEGETATION ENVIRONMENT

2017 ◽  
Vol XLII-2/W5 ◽  
pp. 415-420
Author(s):  
M. Koehl ◽  
Y. Courtois ◽  
S. Guillemin
Keyword(s):  
World War I ◽  
Middle Ages ◽  
Laser Scanning ◽  
Digital Terrain Model ◽  
Point Clouds ◽  
Major Step ◽  
Terrain Model ◽  
Dense Vegetation ◽  
Aerial Photogrammetry ◽  
Pass Through

The Schwartzenbourg castle is a Middle-Ages fortress which was built in 1261. It is situated above the valley of Munster in Alsace, France. It was mainly used as a fortified place and a jail. In the early 15th century, the structure has deteriorated. Even after some repairs, it fell into ruins during the Thirty Years’ war (1618-1648) and stayed uninhabited. During World War I, the German army used the place as a vantage point and also built a blockhouse inside the ruins. Nowadays, the ruins are gradually collapsing and the remains of the old walls are completely covered by thick plants.<br><br> The goal of this project was to create a 3D-model of the site before closing its access, which became too dangerous for people. This modelling is divided into two elements: on one hand, a digital terrain model (DTM) of the site in order to replace the castle and to analyze the background of its original environment; on the other hand, a 3D modelling of the ruins of the castle invaded by the vegetation. Indeed, the main difficulty of the measurement is obviously the dense vegetation which hides the castle. Held back for years outside the castle, it has now become an integral part of the ruins. This vegetation is finally today usually the first threat of heritage buildings. After a preliminary inspection of the site as well as difficulties of the project, the first step consisted of the survey of the whole environment of the site. We will therefore describe the different phases of the survey with the initial implementation of a georeferenced network on site. We will present the terrestrial laser scanning (TLS) surveys, then complementary surveys carried out by aerial photogrammetry. To be implemented, we had to wait for an advanced autumn in order to have as few leaves on trees as possible. The major step of processing of point clouds described in this paper is then the extraction of a DTM by using techniques to pass through the vegetation, or better to segment the points into different classes, one of these that would be the soil i.e. DTM, another consists into wall parts of the ruins.

scholarly journals Using ALS Data to Improve Co-Registration of Photogrammetry-Based Point Cloud Data in Urban Areas

2020 ◽  
Vol 12 (12) ◽  
pp. 1943
Author(s):  
Ranjith Gopalakrishnan ◽  
Daniela Ali-Sisto ◽  
Mikko Kukkonen ◽  
Pekka Savolainen ◽  
Petteri Packalen
Keyword(s):  
Standard Deviation ◽  
Urban Areas ◽  
Laser Scanning ◽  
Point Clouds ◽  
Image Point ◽  
Vertical Coordinate ◽  
Cloud Data ◽  
Suburban Areas ◽  
Aerial Photogrammetry ◽  
Forested Areas

Globally, urban areas are rapidly expanding and high-quality remote sensing products are essential to help guide such development towards efficient and sustainable pathways. Here, we present an algorithm to address a common problem in digital aerial photogrammetry (DAP)-based image point clouds: vertical mis-registration. The algorithm uses the ground as inferred from airborne laser scanning (ALS) data as a reference surface and re-aligns individual point clouds to this surface. We demonstrate the effectiveness of the proposed method for the city of Kuopio, in central Finland. Here, we use the standard deviation of the vertical coordinate values as a measure of the mis-registration. We show that such standard deviation decreased substantially (more than 1.0 m) for a large proportion (23.2%) of the study area. Moreover, it was shown that the method performed better in urban and suburban areas, compared to vegetated areas (parks, forested areas, and so on). Hence, we demonstrate that the proposed algorithm is a simple and effective method to improve the quality and usability of DAP-based point clouds in urban areas.

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