scholarly journals Generation of photoclinometric DTMs for application to transient changes on the surface of comet 67P/Churyumov-Gerasimenko

2019 ◽  
Vol 630 ◽  
pp. A10 ◽  
Author(s):  
Y. Tang ◽  
S. P. D. Birch ◽  
A. G. Hayes ◽  
R. Kirk ◽  
N. Kutsop ◽  
...  
Keyword(s):  
Large Scale ◽  
Shape From Shading ◽  
Small Scale ◽  
Digital Terrain ◽  
Terrain Models ◽  
Rosetta Mission ◽  
The Many ◽  
Pixel Scale ◽  
Comet 67P ◽  
Temporal Coverage

Context. The wide spatial and temporal coverage of 67P/Churyumov-Gerasimenko (67P) by the Rosetta mission has revealed a surface created by scattered large-scale changes and numerous small-scale changes. The many small-scale changes are of particular interest because they are unexpected and ubiquitous. As their topographic relief is often smaller than one meter, which is below the resolution of any shape models, we need higher resolution topography to analyze them properly. Aims. We describe a photoclinometry method that is able to retrieve surface elevations for a single OSIRIS image of the surface of 67P. With this method, we can provide accurate measures, along with error estimates, of the centimeter-scale topography of observed transient changes. Methods. Photoclinometry, or shape-from-shading, estimates heights by examining the light reflection of the surface as dictated by a photometric model under a specified set of viewing geometries. Assuming a standard photometric model for 67P, we can recreate the shading of a surface under specified viewing geometries. The output is a high-resolution height map that matches the original image pixel by pixel. We then provide estimates of the error in the retrieved heights and ensure that our method is valid with a series of checks. Results. We generate digital terrain models (DTMs) with a vertical resolution comparable to or smaller than the pixel scale. This allows us to accurately measure changes in the surface topography on centimeter scales. We find that most changes within the smooth terrains involve the transport or removal of material thinner than one meter.

scholarly journals Post-rendezvous radar properties of comet 67P/CG from the Rosetta Mission: understanding future Earth-based radar observations and the dynamical evolution of comets

2019 ◽  
Vol 489 (2) ◽  
pp. 1667-1683 ◽  
Author(s):  
Essam Heggy ◽  
Elizabeth M Palmer ◽  
Alain Hérique ◽  
Wlodek Kofman ◽  
M Ramy El-Maarry
Keyword(s):  
Large Scale ◽  
Structural Changes ◽  
Dynamical Evolution ◽  
Textural Properties ◽  
Building Blocks ◽  
Cometary Nucleus ◽  
Small Scale ◽  
Small Bodies ◽  
Radar Observations ◽  
Comet 67P

ABSTRACT Radar observations provide crucial insights into the formation and dynamical evolution of comets. This ability is constrained by our knowledge of the dielectric and textural properties of these small-bodies. Using several observations by Rosetta as well as results from the Earth-based Arecibo radio telescope, we provide an updated and comprehensive dielectric and roughness description of Comet 67P/CG, which can provide new constraints on the radar properties of other nuclei. Furthermore, contrary to previous assumptions of cometary surfaces being dielectrically homogeneous and smooth, we find that cometary surfaces are dielectrically heterogeneous ( εr′≈1.6–3.2), and are rough at X- and S-band frequencies, which are widely used in characterization of small-bodies. We also investigate the lack of signal broadening in CONSERT observations through the comet head. Our results suggest that primordial building blocks in the subsurface are either absent, smaller than the radar wavelength, or have a weak dielectric contrast (Δ εr′). To constrain this ambiguity, we use optical albedo measurements by the OSIRIS camera of the freshly exposed subsurface after the Aswan cliff collapse. We find that the hypothetical subsurface blocks should have |Δ εr′|≳0.15, setting an upper limit of ∼ 1 m on the size of 67P/CG's primordial building blocks if they exist. Our analysis is consistent with a purely thermal origin for the ∼ 3 m surface bumps on pit walls and cliff-faces, hypothesized to be high-centred polygons formed from fracturing of the sintered shallow ice-bearing subsurface due to seasonal thermal expansion and contraction. Potential changes in 67P/CG's radar reflectivity at these at X- and S-bands can be associated with large-scale structural changes of the nucleus rather than small-scale textural ones. Monitoring changes in 67P/CG's radar properties during repeated close-approaches via Earth-based observations can constrain the dynamical evolution of its cometary nucleus.

scholarly journals A REGISTRATION METHOD OF POINT CLOUDS COLLECTED BY MOBILE LIDAR USING SOLELY STANDARD LAS FILES INFORMATION

2017 ◽  
Vol XLII-1/W1 ◽  
pp. 121-128 ◽  
Author(s):  
L. Gézero ◽  
C. Antunes
Keyword(s):  
Point Cloud ◽  
Large Scale ◽  
Auxiliary Information ◽  
Point Clouds ◽  
Registration Method ◽  
Digital Terrain ◽  
Terrain Models ◽  
Dense Point ◽  
Fully Automatic ◽  
Method Point

In the last few years, LiDAR sensors installed in terrestrial vehicles have been revealed as an efficient method to collect very dense 3D georeferenced information. The possibility of creating very dense point clouds representing the surface surrounding the sensor, at a given moment, in a very fast, detailed and easy way, shows the potential of this technology to be used for cartography and digital terrain models production in large scale. However, there are still some limitations associated with the use of this technology. When several acquisitions of the same area with the same device, are made, differences between the clouds can be observed. The range of that differences can go from few centimetres to some several tens of centimetres, mainly in urban and high vegetation areas where the occultation of the GNSS system introduces a degradation of the georeferenced trajectory. Along this article a different method point cloud registration is proposed. In addition to the efficiency and speed of execution, the main advantages of the method are related to the fact that the adjustment is continuously made over the trajectory, based on the GPS time. The process is fully automatic and only information recorded in the standard LAS files is used, without the need for any auxiliary information, in particular regarding the trajectory.

scholarly journals The 67P/Churyumov–Gerasimenko observation campaign in support of the Rosetta mission

2017 ◽  
Vol 375 (2097) ◽  
pp. 20160249 ◽  
Author(s):  
C. Snodgrass ◽  
M. F. A'Hearn ◽  
F. Aceituno ◽  
V. Afanasiev ◽  
S. Bagnulo ◽  
...  
Keyword(s):  
Large Scale ◽  
Activity Patterns ◽  
Mission Planning ◽  
Context Information ◽  
Large Collection ◽  
Future Studies ◽  
Early Results ◽  
Rosetta Mission ◽  
Comet 67P

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov–Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively ‘well-behaved’ comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends—in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies. This article is part of the themed issue ‘Cometary science after Rosetta’.

scholarly journals AUTOMATED MAPPING OF PERMANENT PRESERVATION AREAS ON HILLTOPS

CERNE ◽  
2016 ◽  
Vol 22 (1) ◽  
pp. 111-120 ◽  
Author(s):  
Guilherme de Castro Oliveira ◽  
Elpidio Inacio Fernandes Filho
Keyword(s):  
Large Scale ◽  
Digital Terrain Model ◽  
Map Algebra ◽  
Automated Mapping ◽  
Model Builder ◽  
Terrain Model ◽  
Digital Terrain ◽  
Forest Code ◽  
New Forest ◽  
The Many

ABSTRACT Permanent Preservation Areas (PPAs) on hilltops are among the many areas protected by the New Forest Code in Brazil. Mapping of these involves difficult interpretation and application of the Law, as well a complex task of translating it in map algebra. This paper aims to present, in detail, a methodological model for delimitation of PPAs on hilltops, according to the Brazilian new Forest Code (NFC, Law 12,651/2012). The model was developed in Model Builder for ArcGIS 10.2, and is able to map the PPAs in any digital terrain model. However, field validations are required to verify its efficiency. There is need for legal standardization of criteria that may cause subjectivity in delimitation. The organization of these data on a large scale is very important, as example, to the Rural Environmental Registry, which provides georeferencing of all rural properties and its protected areas in Brazil.

Cattle

1984 ◽  
Vol 8 ◽  
pp. 83-89
Author(s):  
Ian B. Howie
Keyword(s):  
Large Scale ◽  
Production Systems ◽  
Farming System ◽  
Small Scale ◽  
Market Forces ◽  
Poultry Production ◽  
Short Term ◽  
Fully Integrated ◽  
Beef Producers ◽  
The Many

Matching production to the markets for meat makes the assumption that individual producers can have an influence on market forces. This may well apply nowadays to some of the very large scale poultry production units but, individually, beef producers can have little if any influence on the marketing scene. Although there are farmers who produce several hundred fat cattle a year, the bulk of the beef produced comes from fairly small scale producers. Much of beef production is on a fairly haphazard basis with little or no recording or budgeting.Nevertheless, small scale producers and feeders who move in and out of the market can exploit local or short-term, favourable, market fluctuations and, with skilful buying and selling, make good profits on a quick turnover. Larger scale producers who have pre-planned fully integrated production systems cannot react as quickly to any great extent to short-term marketing opportunities. I regard marketing as only one of the many variable factors to be taken into account when planning a beef enterprise within a whole farming system, in which it is likely to be one of a number of enterprises which have to be kept in balance.

Prediction of soil salinity risk by digital terrain modeling in the Canadian prairies

2000 ◽  
Vol 80 (3) ◽  
pp. 455-463 ◽  
Author(s):  
I. V. Florinsky ◽  
R. G. Eilers ◽  
G. W. Lelyk
Keyword(s):  
Soil Salinity ◽  
Risk Index ◽  
Small Scale ◽  
Canadian Prairies ◽  
Digital Terrain ◽  
Terrain Models ◽  
Digital Elevation ◽  
Soil Salinisation ◽  
Elevation Model ◽  
Digital Terrain Modeling

Soil salinisation is a typical problem for the Canadian prairies. At macro-topographic scale, build-up of salts occurs in depressions. However, this relationship is not displayed on existing small-scale maps of soil salinity. To improve these maps, one can use a concept of accumulation, transition and dissipation zones of the landsurface. The concept allows one to reveal depressions (topographically expressed accumulation zones) using digital models of horizontal and vertical curvatures, or accumulation and mean curvatures derived from a digital elevation model. We applied the concept of accumulation, transition and dissipation zones to improve an existing small-scale map of the salinity risk index for the prairies and adjacent areas. A comparison of the old and the improved maps demonstrated that once data on depressions have been taken into account, areas marked by salinity risk decreased significantly. We suggest that the method used may prevent an overestimation in predictions of soil cover degradation due to salinisation. The method used can also reveal saline areas linked with discharges of saline aquifers. This is because sites marked by high discharges of groundwater usually relate to sites of intensive fracturing of geological materials, which are closely associated with topographically expressed accumulation zones. Key words: Digital terrain models, topography, soil salinisation, mapping

scholarly journals ANALYTICAL AND DIGITAL PHOTOGRAMMETRIC GEODATA PRODUCTION SYSTEMS (A COMPARISON TEST)

2012 ◽  
Vol 33 (2) ◽  
pp. 50-54 ◽  
Author(s):  
Birutė Ruzgienė ◽  
Edita Aleknienė
Keyword(s):  
Large Scale ◽  
Production Systems ◽  
Digital Terrain Model ◽  
Terrain Model ◽  
Digital Mapping ◽  
Digital Terrain ◽  
Terrain Models ◽  
Mapping System ◽  
Mapping Technology ◽  
Images Processing

Up-to-date mapping technologies are in the middle of transition from analytical to digital. The usage of new methods and technologies implies the desire to increase mapping capability. Despite that, analytical and digital methods may be used simultaneously, thus getting more efficient results. The research objective is to present some aspects of functionality of both digital and analytical photogrammetric mapping approaches in generating 3D geodata. The experimental results show which of the two methods could lead to a more flexible mapping production in consideration of the following criteria: accuracy, flexibility, time and cost. The main result of investigations shows, that the orthophoto generation is successfully using fully automatic systems. The digital terrain models created by two technologies are almost the same due to time-consuming. Therefore more time is required for the Digital Photogrammetric System when the terrain is rougher. Despite the fact that digital photogrammetric mapping technology drastically develops, there is no doubt that analytical photogrammetry is still a significant production system for large‐scale mapping. The results demonstrate that there is not too much difference in accuracy between the analytical and the digital 14 μm pixel size images processing. The interpretation capability of experimental test area in the Digital Photogrammetric System was more complicated as it was by the analytical plotter. Two systems integrations have been foreseen. Digital terrain model obtained by the analytical plotter can be transferred to digital mapping system for orthophoto generation.

scholarly journals How Well Do We Know Europa’s Topography? An Evaluation of the Variability in Digital Terrain Models of Europa

2021 ◽  
Vol 13 (24) ◽  
pp. 5097
Author(s):  
Michael T. Bland ◽  
Randolph L. Kirk ◽  
Donna M. Galuszka ◽  
David P. Mayer ◽  
Ross A. Beyer ◽  
...  
Keyword(s):  
Horizontal Resolution ◽  
Data Sets ◽  
Digital Terrain Models ◽  
Matching Accuracy ◽  
Extraterrestrial Life ◽  
Correlation Kernel ◽  
Digital Terrain ◽  
Terrain Models ◽  
Ice Shell ◽  
Pixel Scale

Jupiter’s moon Europa harbors one of the most likely environments for extant extraterrestrial life. Determining whether Europa is truly habitable requires understanding the structure and thickness of its ice shell, including the existence of perched water or brines. Stereo-derived topography from images acquired by NASA Galileo’s Solid State Imager (SSI) of Europa are often used as a constraint on ice shell structure and heat flow, but the uncertainty in such topography has, to date, not been rigorously assessed. To evaluate the current uncertainty in Europa’s topography we generated and compared digital terrain models (DTMs) of Europa from SSI images using both the open-source Ames Stereo Pipeline (ASP) software and the commercial SOCET SET® software. After first describing the criteria for assessing stereo quality in detail, we qualitatively and quantitatively describe both the horizontal resolution and vertical precision of the DTMs. We find that the horizontal resolution of the SOCET SET® DTMs is typically 8–11× the root mean square (RMS) pixel scale of the images, whereas the resolution of the ASP DTMs is 9–13× the maximum pixel scale of the images. We calculate the RMS difference between the ASP and SOCET SET® DTMs as a proxy for the expected vertical precision (EP), which is a function of the matching accuracy and stereo geometry. We consistently find that the matching accuracy is ~0.5 pixels, which is larger than well-established “rules of thumb” that state that the matching accuracy is 0.2–0.3 pixels. The true EP is therefore ~1.7× larger than might otherwise be assumed. In most cases, DTM errors are approximately normally distributed, and errors that are several times the derived EP occur as expected. However, in two DTMs, larger errors (differences) occur and correlate with real topography. These differences primarily result from manual editing of the SOCET SET® DTMs. The product of the DTM error and the resolution is typically 4–8 pixel2 if calculated using the RMS image scale for SOCET SET® DTMs and the maximum images scale for the ASP DTMs, which is consistent with recent work using martian data sets and suggests that the relationship applies more broadly. We evaluate how ASP parameters affect DTM quality and find that using a smaller subpixel refinement kernel results in DTMs with smaller (better) resolution but, in some cases, larger gaps, which are sometimes reduced by increasing the size of the correlation kernel. We conclude that users of ASP should always systematically evaluate the choice of parameters for a given dataset.

ANTHROPOGENIC CHANGES OF THE “OLD COPPER BASIN” AREA LANDSCAPE (NORTH-SUDETIC SYNCLINORIUM) IN THE LIGHT OF LIDAR-BASED GEOMORPHOMETRIC ANALYSIS AND ARCHIVAL DATA

2017 ◽  
pp. 0-0
Author(s):  
Aleksander Kowalski ◽  
Krzysztof Maciejak ◽  
Jurand Wojewoda ◽  
Adam Kozłowski ◽  
Paweł Raczyński
Keyword(s):  
Spatial Data ◽  
Small Scale ◽  
The North ◽  
Ground Deformations ◽  
Digital Terrain ◽  
Terrain Models ◽  
Sw Poland ◽  
The Subject ◽  
And Storage ◽  
Basin Area

While the history, techniques of exploitation and deposit parameters of the copper ores in the North-Sudetic Synclinorium have been the subject of numerous investigations, the transformations of the terrain in the so-called “Old Copper Basin” (Lower Silesia, SW Poland) have not been analysed in detail before. This paper is intended to complement this gap. The authors present the results of the detailed geomorphometric analysis of the post-mining forms related directly to the copper mining. The LiDAR-based, high-resolution Digital Terrain Models (DTMs), which have been used in the analysis and description of the landforms, are currently considered as the most accurate and precise 3D-spatial data available in the numerical form. The following anthropogenic forms are distinguished in the study area: large- and small-scale ground deformations (depressions and small sinkholes), abandoned quarries, and forms associated with the exploitation and storage of the flotation wastes – post-flotation tailings and dumps. Our investigations have allowed visualization of the spatial distribution of the forms, estimation of their total volume as well as perspectives of their reclamation and protection.

scholarly journals ASSESMENT OF THE INFLUENCE OF UAV IMAGE QUALITY ON THE ORTHOPHOTO PRODUCTION

2015 ◽  
Vol XL-1/W4 ◽  
pp. 1-8 ◽  
Author(s):  
D. Wierzbicki ◽  
M. Kedzierski ◽  
A. Fryskowska
Keyword(s):  
Large Scale ◽  
Digital Terrain Model ◽  
Image Data ◽  
Weather Conditions ◽  
Noticeable Increase ◽  
Terrain Model ◽  
Digital Terrain ◽  
Lighting Conditions ◽  
Terrain Models ◽  
Uav Image

Over the past years a noticeable increase of interest in using Unmanned Aerial Vehicles (UAV) for acquiring low altitude images has been observed. This method creates new possibilities of using geodata captured from low altitudes to generate large scale orthophotos. Because of comparatively low costs, UAV aerial surveying systems find many applications in photogrammetry and remote sensing. One of the most significant problems with automation of processing of image data acquired with this method is its low accuracy. This paper presents the following stages of acquisition and processing of images collected in various weather and lighting conditions: aerotriangulation, generating of Digital Terrain Models (DTMs), orthorectification and mosaicking. In the research a compact, non-metric camera, mounted on a fuselage powered by an electric motor was used. The tested area covered flat, agricultural and woodland terrains. Aerotriangulation and point cloud accuracy as well as generated digital terrain model and mosaic exactness were examined. Dense multiple image matching was used as a benchmark. The processing and analysis were carried out with INPHO UASMaster programme. Based on performed accuracy analysis it was stated that images acquired in poor weather conditions (cloudy, precipitation) degrade the final quality and accuracy of a photogrammetric product by an average of 25%.

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