Relevant Publications
|
Title: |
|
Searchable Sky Coverage of Astronomical Observations: Footprints and Exposures |
|
Authors: |
|
Budavari, Tamas;
Szalay, Alex;
Fekete, Gyorgy |
|
Publication: |
|
eprint arXiv:1005.2606 |
|
Publication Date: |
|
05/2010 |
|
Origin: |
|
ARXIV |
|
Keywords: |
|
Astrophysics - Instrumentation and Methods for Astrophysics |
|
Comment: |
|
11 pages, 7 figures, submitted to PASP |
|
Bibliographic Code: |
|
2010arXiv1005.2606B |
Abstract
Sky coverage is one of the most important pieces of information about
astronomical observations. We discuss possible representations, and present
algorithms to create and manipulate shapes consisting of generalized spherical
polygons with arbitrary complexity and size on the celestial sphere. This shape
specification integrates well with our Hierarchical Triangular Mesh indexing
toolbox, whose performance and capabilities are enhanced by the advanced
features presented here. Our portable implementation of the relevant spherical
geometry routines comes with wrapper functions for database queries, which are
currently being used within several scientific catalog archives including the
Sloan Digital Sky Survey, the Galaxy Evolution Explorer and the Hubble Legacy
Archive projects as well as the Footprint Service of the Virtual Observatory.
|
Title: |
|
Footprint Services for Everyone |
|
Authors: |
|
Budavári, T.;
Dobos, L.;
Szalay, A. S.;
Greene, G.;
Gray, J.;
Rots, A. H. |
|
Publication: |
|
Astronomical Data Analysis Software and Systems XVI ASP Conference Series, Vol.
376, proceedings of the conference held 15-18 October 2006 in Tucson, Arizona,
USA. Edited by Richard A. Shaw, Frank Hill and David J. Bell., p.559 |
|
Publication Date: |
|
10/2007 |
|
Origin: |
|
ASP |
|
Bibliographic Code: |
|
2007ASPC..376..559B |
Abstract
We present high-level user and web services for dealing with astronomical survey
geometry of arbitrary size and complexity. Based on our high-performance
spherical library, we built an on-line public repository of footprints
pre-loaded with the coverage of some of the most widely used datasets today
including the Sloan Digital Sky Survey, the Galaxy Evolution Explorer and the
Hubble Space Telescope exposures. We publish a web-based toolkit that enables
advanced spatial searches for regions of interest on the sky, Boolean operations
on selected footprints (union, intersection), on-the-fly visualization, and
exact area computation. We also provide an easy-to-use interactive footprint
editor, as well as a simple upload facility. The results of the searches and
region manipulations can be saved and published on the footprint server or
downloaded in various formats, including ASCII and the VO-compliant Space-Time
Coordinate (STC) region representation.
|
Title: |
|
Chapter 9: Web-based Tools - Footprint Services in the Virtual Observatory |
|
Authors: |
|
Budavari, T.;
Szalay Gyoergy Fekete, A. S.;
Dobos, L.;
Greene, G.;
Gray, J.;
Rots, A. H. |
|
Publication: |
|
The National Virtual Observatory: Tools and Techniques for Astronomical
Research. ASP Conference Series, Vol. 382. Edited by M.J. Graham, M.J.
Fitzpatrick, and T.A. McGlynn. San Francisco: Astronomical Society of the
Pacific, 2007., p.75 |
|
Publication Date: |
|
00/2007 |
|
Origin: |
|
ASPC |
|
Bibliographic Code: |
|
2007ASPC..382...75B |
Abstract
There is much more to astronomical observations than just source catalogs. For
example, when working with multiple observations at different wavelengths,
knowing their precise coverage is very important, e.g. to look for dropouts, and
can often be very difficult when the most significant observations also have the
most complex geometry. This functionality has been missing almost entirely from
the toolbox of many astronomers.
The sphere is arguably the most beautiful object and certainly the simplest one.
Yet its surface has a strange topology: travel in any given direction and you
will eventually return to the starting point. As trivial and banal as it sounds,
this has been a source of frustration of many scientists, including astronomers
who observe objects on the celestial sphere. Spherical geometry is difficult and
there are no easy solutions or shortcuts, especially if one is after an
efficient algorithm.
Abstract
We describe a method to subdivide the surface of a sphere into spherical
triangles of similar, but not identical, shapes and sizes. The Hierarchical
Triangular Mesh (HTM) is a quad-tree that is particularly good at supporting
searches at different resolutions, from arc seconds to hemispheres. The
subdivision scheme is universal, providing the basis for addressing and for fast
lookups. The HTM provides the basis for an efficient geospatial indexing scheme
in relational databases where the data have an inherent location on either the
celestial sphere or the Earth. The HTM index is superior to cartographical
methods using coordinates with singularities at the poles. We also describe a
way to specify surface regions that efficiently represent spherical query areas.
This article presents the algorithms used to identify the HTM triangles covering
such regions.
|
Title: |
|
Using Table Valued Functions in SQL Server 2005 To Implement a Spatial Data
Library |
|
Authors: |
|
Gray, Jim;
Szalay, Alex;
Fekete, Gyorgy |
|
Publication: |
|
eprint arXiv:cs/0701163 |
|
Publication Date: |
|
01/2007 |
|
Origin: |
|
ARXIV |
|
Keywords: |
|
Computer Science - Databases, Computer Science - Computational Engineering,
Finance, and Science |
|
Bibliographic Code: |
|
2007cs........1163G |
Abstract
This article explains how to add spatial search functions (point-near-point and
point in polygon) to Microsoft SQL Server 2005 using C# and table-valued
functions. It is possible to use this library to add spatial search to your
application without writing any special code. The library implements the
public-domain C# Hierarchical Triangular Mesh (HTM) algorithms from Johns
Hopkins University. That C# library is connected to SQL Server 2005 via a set of
scalar-valued and table-valued functions. These functions act as a spatial
index.
|
Title: |
|
New Features for VO-Enabled Data Intensive Science with the SDSS Data Release 3 |
|
Authors: |
|
Thakar, A. R.;
Szalay, A. S.;
O'Mullane, W.;
Budavári, T.;
Nieto-Santisteban, M. A.;
Fekete, G.;
Li, N.;
Carliles, S.;
Gray, J.;
Lupton, R. |
|
Publication: |
|
Astronomical Data Analysis Software and Systems XIV ASP Conference Series, Vol.
347, Proceedings of the Conference held 24-27 October, 2004 in Pasadena,
California, USA. Edited by P. Shopbell, M. Britton, and R. Ebert. San Francisco:
Astronomical Society of the Pacific, 2005., p.684 |
|
Publication Date: |
|
12/2005 |
|
Origin: |
|
ASP |
|
Bibliographic Code: |
|
2005ASPC..347..684T |
Abstract
We describe new and enhanced features for data access with the third data
release (DR3) of the SDSS, particularly in the context of data intensive science
and the VO. These include several enhancements to the CasJobs batch query
workbench system, improved JPEG color images in the Visual Tools, extensive
usage and traffic logging with harvesting of multiple remote site logs,
enhancements to the HTM spatial library and a more versatile object crossid
facility. We briefly describe these features and list future enhancements
anticipated with SQLServer Yukon.
|
Title: |
|
HTM2: Spatial Toolkit for the Virtual Observatory |
|
Authors: |
|
Fekete, G.;
Szalay, A. S.;
Gray, J. |
|
Publication: |
|
Astronomical Data Analysis Software and Systems (ADASS) XIII, Proceedings of the
conference held 12-15 October, 2003 in Strasbourg, France. Edited by Francois
Ochsenbein, Mark G. Allen and Daniel Egret. ASP Conference Proceedings, Vol.
314. San Francisco: Astronomical Society of the Pacific, 2004., p.289 |
|
Publication Date: |
|
07/2004 |
|
Origin: |
|
AUTHOR |
|
Bibliographic Code: |
|
2004ASPC..314..289F |
Abstract
The hierarchical tringular mesh (HTM) is a discrete foundation for
describing location, size and shape on the celestial sphere. Indices
derived from HTM descriptors are used in a relational database for
managing spatial information. Some of the new features available in
the current implementation support operations such as the ability to
perform searches based on arbitrary polygons, convex hulls of
polygons or any region bounded by great or small circles. These
functions are reached through a language that is implemented as an
extension to MSQL Server 2000 relational database engine. The heart
of the HTM tools can also be used through various interfaces in
several langugages, like C++, C# and Java. An extensive XML
specification for describing spatial structures to support spatial
queries is also under development.
|
Title: |
|
Splitting the Sky - HTM and HEALPix |
|
Authors: |
|
O'Mullane, W.;
Banday, A. J.;
Górski, K. M.;
Kunszt, P.;
Szalay, A. S. |
|
Affiliation: |
|
AA(Astrophysics Division, Space Science Department of ESA, ESTEC), AB(MPI für
Astrophysik), AC(European Southern Observatory (ESO)), AD(The Johns Hopkins
University), AE(The Johns Hopkins University) |
|
Publication: |
|
Mining the Sky: Proceedings of the MPA/ESO/MPE Workshop Held at Garching,
Germany, July 31 - August 4, 2000, ESO ASTROPHYSICS SYMPOSIA. ISBN
3-540-42468-7. Edited by A.J. Banday, S. Zaroubi, and M. Bartelmann.
Springer-Verlag, 2001, p. 638 |
|
Publication Date: |
|
00/2001 |
|
Origin: |
|
ADS;
SPRINGER |
|
Abstract Copyright: |
|
(c) 2001: Springer-Verlag |
|
Comment: |
|
ISBN: 3-540-42468-7 |
|
DOI: |
|
10.1007/10849171_84 |
|
Bibliographic Code: |
|
2001misk.conf..638O |
Abstract
Mission data sets are increasing in size and complexity. To enable efficient
processing and storage of such data sets a tessellation scheme may be adopted.
The Hierarchical Triangular Mesh (HTM) and the Hierarchical Equal Area
isoLatitude Pixelisation (HEALPix) schemes are two popular schemes each with
software tools available to exploit their particular properties. The initial
drivers behind these two schemes are quite different but as their use continues
the complimentary facilities of each package will become more relevant. Here we
describe the motivation and facilities of HEALPix and HTM, we ask if it is
possible to combine these schemes or make use of them in a combined manner and
say why we may wish to do this.
|
Title: |
|
The Hierarchical Triangular Mesh |
|
Authors: |
|
Kunszt, Peter Z.;
Szalay, Alexander S.;
Thakar, Aniruddha R. |
|
Affiliation: |
|
AA(Johns Hopkins University), AB(Johns Hopkins University), AC(Johns Hopkins
University) |
|
Publication: |
|
Mining the Sky: Proceedings of the MPA/ESO/MPE Workshop Held at Garching,
Germany, July 31 - August 4, 2000, ESO ASTROPHYSICS SYMPOSIA. ISBN
3-540-42468-7. Edited by A.J. Banday, S. Zaroubi, and M. Bartelmann.
Springer-Verlag, 2001, p. 631 |
|
Publication Date: |
|
00/2001 |
|
Origin: |
|
ADS;
SPRINGER |
|
Abstract Copyright: |
|
(c) 2001: Springer-Verlag |
|
Comment: |
|
ISBN: 3-540-42468-7 |
|
DOI: |
|
10.1007/10849171_83 |
|
Bibliographic Code: |
|
2001misk.conf..631K |
Abstract
The Hierarchical Triangular Mesh (HTM) is a method to subdivide the spherical
surface into triangles of nearly equal shape and size. The HTM gives us a very
efficient indexing method for objects localized on the sphere. We also developed
a simple geometrical method to define an arbitrary area on the sphere which can
be intersected by the HTM, returning the triangles covered by the area. Thus we
have a powerful querying tool to find objects on the sphere by location. In this
contribution we define the Hierarchical Triangular Mesh, the geometric querying
and we give concrete numbers of the performance of the current implementation.
|
