47 research outputs found
Minimising systematic error surfaces in digital elevation models using oblique convergent imagery
There are increasing opportunities to use consumer-grade digital cameras, particularly
if accurate spatial data can be captured. Research recently conducted at
Loughborough University identified residual systematic error surfaces or domes discernible
in digital elevation models (DEMs). These systematic effects are often associated
with such cameras and are caused by slightly inaccurate estimated lens
distortion parameters. A methodology that minimises the systematic error surfaces
was therefore developed, using a mildly convergent image configuration in a vertical
perspective. This methodology was tested through simulation and a series of practical
tests. This paper investigates the potential of the convergent configuration to minimise
the error surfaces, even if the geometrically more complex oblique perspective is used.
Initially, simulated data was used to demonstrate that an oblique convergent image
configuration can minimise remaining systematic error surfaces using various imaging
angles. Additionally, practical tests using a laboratory testfield were conducted to
verify results of the simulation. The need to develop a system to measure the topographic
surface of a flooding river provided the opportunity to verify the findings of
the simulation and laboratory test using real data. Results of the simulation process,
the laboratory test and the practical test are reported in this paper and demonstrate
that an oblique convergent image configuration eradicates the systematic error surfaces
which result from inaccurate lens distortion parameters. This approach is significant
because by removing the need for an accurate lens model it effectively improves
the accuracies of digital surface representations derived using consumer-grade digital
cameras. Carefully selected image configurations could therefore provide new opportunities
for improving the quality of photogrammetrically acquired data
Cultural Heritage Recording Utilising Low-Cost Closerange Photogrammetry
This paper was presented at the CIPA 23rd International Symposium, 12 â 16 September 2011, Prague, Czech Republic:http://www.conferencepartners.cz/cipa/Cultural heritage is under a constant threat of damage or even destruction and comprehensive
and accurate recording is necessary to attenuate the risk of losing heritage or serve as basis for
reconstruction. Cost effective and easy to use methods are required to record cultural heritage, particularly
during a world recession, and close-range photogrammetry has proven potential in this area. Off-the-shelf
digital cameras can be used to rapidly acquire data at low cost, allowing non-experts to become involved.
Exterior orientation of the camera during exposure ideally needs to be established for every image,
traditionally requiring known coordinated target points. Establishing these points is time consuming and
costly and using targets can be often undesirable on sensitive sites. MEMS-based sensors can assist in
overcoming this problem by providing small-size and low-cost means to directly determine exterior
orientation for close-range photogrammetry. This paper describes development of an image-based
recording system, comprising an off-the-shelf digital SLR camera, a MEMS-based 3D orientation sensor and
a GPS antenna. All system components were assembled in a compact and rigid frame that allows calibration
of rotational and positional offsets between the components. The project involves collaboration between
English Heritage and Loughborough University and the intention is to assess the systemâs achievable
accuracy and practicability in a heritage recording environment. Tests were conducted at Loughborough
University and a case study at St. Catherineâs Oratory on the Isle of Wight, UK. These demonstrate that the
data recorded by the system can indeed meet the accuracy requirements for heritage recording at medium
accuracy (1-4cm), with either a single or even no control points. As the recording system has been
configured with a focus on low-cost and easy-to-use components, it is believed to be suitable for heritage
recording by non-specialists. This offers the opportunity for lay people to become more involved in their
local heritage, an important aspiration identified by English Heritage. Recently, mobile phones
(smartphones) with integrated camera and MEMS-based orientation and positioning sensors have become
available. When orientation and position during camera exposure is extracted, these phones establish offthe-
shelf systems that can facilitate image-based recording with direct exterior orientation determination.
Due to their small size and low-cost they have potential to further enhance the involvement of lay-people in
heritage recording. The accuracy currently achievable will be presented also
Hydrodynamic Behaviour of a Two-Stage Channel with Horizontal and Inclined Floodplains: A Numerical Investigation
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv
The accuracy of a river bed moulding/casting system and the effectiveness of a low-cost digital camera for recording river bed fabric
Digital photogrammetry has been used to develop and test an artificial
river bed moulding and casting system, which allows the pebbles within a
coarse grain river bed to be recreated for hydraulic research in a laboratory
flow channel or flume. Imagery of both the original streambed and the cast
facsimile was acquired using a non-metric Kodak DCS460 digital camera
and digital elevation models and orthophotographs were derived and
compared to assess the accuracy of the moulding and casting system. These
comparative tests proved to be critical in modifying and developing the
system.
Additional imagery was obtained in the field using a non-metric
Olympus C3030 âcompactâ digital camera to assess whether far cheaper
camera technology could deliver data appropriate for such comparative
examinations. Internal calibration parameter sets and data that were
generated were compared with data obtained by the non-metric Kodak
DCS460. These tests demonstrate that digital sensors built around highquality
35 mm professional camera bodies and lenses are required for
comparative examinations and for similar system development
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
Polypharmacy among anabolic-androgenic steroid users: A descriptive metasynthesis
Background: As far as we are aware, no previous systematic review and synthesis of the qualitative/descriptive literature on polypharmacy in anabolic-androgenic steroid(s) (AAS) users has been published. Method: We systematically reviewed and synthesized qualitative/descriptive literature gathered from searches in electronic databases and by inspecting reference lists of relevant literature to investigate AAS users' polypharmacy. We adhered to the recommendations of the UK Economic and Social Research Council's qualitative research synthesis manual and the PRISMA guidelines. Results: A total of 50 studies published between 1985 and 2014 were included in the analysis. Studies originated from 10 countries although most originated from United States (n = 22), followed by Sweden (n = 7), England only (n = 5), and the United Kingdom (n = 4). It was evident that prior to their debut, AAS users often used other licit and illicit substances. The main ancillary/supplementary substances used were alcohol, and cannabis/cannabinoids followed by cocaine, growth hormone, and human chorionic gonadotropin (hCG), amphetamine/meth, clenbuterol, ephedra/ephedrine, insulin, and thyroxine. Other popular substance classes were analgesics/opioids, dietary/nutritional supplements, and diuretics. Our classification of the various substances used by AAS users resulted in 13 main groups. These non-AAS substances were used mainly to enhance the effects of AAS, combat the side effects of AAS, and for recreational or relaxation purposes, as well as sexual enhancement. Conclusions: Our findings corroborate previous suggestions of associations between AAS use and the use of other licit and illicit substances. Efforts must be intensified to combat the debilitating effects of AAS-associated polypharmacy
Whole-genome sequencing reveals host factors underlying critical COVID-19
Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2â4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genesâincluding reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)âin critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease
The impact of human immunodeficiency virus (HIV) service scale-up on mechanisms of accountability in Zambian primary health centres: a case-based health systems analysis
Whole-genome sequencing reveals host factors underlying critical COVID-19
Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genesâincluding reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)âin critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease