arXiv subjects

Keith S. Cover

Publications and source records attributed to Keith S. Cover.

4 recordsLinked to original sources

arXiv2017

Improved visualisation of brain arteriovenous malformations using color intensity projections with hue cycling

Color intensity projections (CIP) have been shown to improve the visualisation of greyscale angiography images by combining greyscale images into a single color image. A key property of the combined CIP image is the encoding of the arrival time information from greyscale images into the hue of the color in the CIP image. A few minor improvements to the calculation of the CIP image are introduced that substantially improve the quality of the visualisation. One improvement is interpolating of the greyscale images in time before calculation of the CIP image. A second is the use of hue cycling - where the hue of the color is cycled through more than once in an image. The hue cycling allows the variation of the hue to be concentrated in structures of interest. If there is a zero time point hue cycling can be applied after zero time and before zero time can be indicated by greyscale. If there is an end time point hue cycling can be applied before the end time and pixels can be set to black after the end time. An angiogram of a brain is used to demonstrate the substantial improvements hue cycling brings to CIP images. A third improvement is the use of maximum intensity projection for 2D rendering of a 3D CIP image volume. A fourth improvement allowing interpreters to interactively adjust the phase of the hue via standard contrast - brightness controls using lookup tables. Other potential applications of CIP are also mentioned.

cs.GR↗

arXiv2012

Improved visual detection of moving objects in astronomical images using color intensity projections with hue cycling

While fully automated methods for detecting faint moving objects in astronomical images - such as Kuiper belt objects (KBOs) - are constantly improving, visual detection still has a role to play especially when the fixed background is cluttered with stars. Color intensity projections (CIPs) using hue cycling - which combines a sequence of greyscale images into a single color image - aids in the visual detection of moving objects by highlighting them using color in an intuitive way. To demonstrate the usefulness of CIPs in detecting faint moving objects a sequence of 16 images from the SuprimeCam camera of the Subaru telescope were combined into a CIPs image. As well has making even faint moving objects easier to visually detect against a cluttered background, CCD artefacts were also more easily recognisable. The new Hyper SuprimeCam for the Subaru telescope - which will allow many short exposure images to be acquired with little dead time between images - should provide ideal data for use with the CIPs algorithm. In addition, the current search for KBOs to be targeted by the New Horizon's spacecraft after its flyby of Pluto provides an excellent test case for the state of the art in faint moving object detection against a cluttered background.

astro-ph.IM↗

arXiv2009

Differences at low l in Planck's first light sky map of the cosmic microwave background from WMAP's and COBE's

The recent release of the first light sky map of the cosmic microwave background (CMB) from the Planck satellite provides an initial opportunity for comparison with the WMAP and COBE sky maps and their reconstruction algorithms. The precision of the match between Planck's and WMAP's anisotropies below several degrees in size, which corresponds to spherical harmonics with high l, provides confidence that the differences between the anisotropies at low l are substantial. If the Planck first light sky map is taken as the gold standard, the results seem to suggest the low l components of the WMAP map and a considerable part of the COBE sky map have a similar reconstruction artefact. As the Planck first light sky map covers only about 10% of the sky, any conclusions drawn from this comparison are speculative but deserving of further investigation.

physics.gen-ph↗

arXiv2009

Sky maps without anisotropies in the cosmic microwave background are a better fit to WMAP's uncalibrated time ordered data than the official sky maps

The purpose of this reanalysis of the WMAP uncalibrated time ordered data (TOD) was two fold. The first was to reassess the reliability of the detection of the anisotropies in the official WMAP sky maps of the cosmic microwave background (CMB). The second was to assess the performance of a proposed criterion in avoiding systematic error in detecting a signal of interest. The criterion was implemented by testing the null hypothesis that the uncalibrated TOD was consistent with no anisotropies when WMAP's hourly calibration parameters were allowed to vary. It was shown independently for all 20 WMAP channels that sky maps with no anisotropies were a better fit to the TOD than those from the official analysis. The recently launched Planck satellite should help sort out this perplexing result.

physics.gen-ph↗