1 2\chapter{Surveys} 3\label{ch:surveys} 4\chapterauthor*{Guillaume Chéreau} 5 6\section{Introduction} 7\label{sec:surveys:introduction} 8 9 10A \indexterm{sky survey} \newFeature{0.18.0} is a map of the sky stored as a hierarchical set of a potentially 11large number of smaller images (called tiles). The advantage compared to a 12regular texture is that we need to render only the visible tiles of a potentially gigantic image at the 13lowest resolution needed. This is particularly interesting for rendering 14online images that can be stored on a server, while the client only has 15to download the parts he currently uses. 16 17Since version 0.18.0, Stellarium added some preliminary support for loading and 18rendering online surveys in the \indexterm{Hierarchical Progressive Surveys} (HiPS) format, 19developed by the \indexterm{International Virtual Observatory Alliance}. 20A full description of the format can be found on the IVOA website\footnote{% 21\url{https://www.ivoa.net/documents/HiPS/20170519/REC-HIPS-1.0-20170519.pdf}}. 22 23\section{Hipslist file and default surveys} 24\label{sec:surveys:hipslistFile} 25 26Hipslist files are text files used to describe catalogs of HiPS surveys. The 27full specification is part of the HiPS format, and looks like that: 28 29\begin{configfileScr} 30# Example of a hipslist file. 31# Date: 2018-03-19 32 33hips_service_url = https://data.stellarium.org/surveys/callisto 34hips_release_date = 2018-03-18T14:01Z 35hips_status = public mirror clonableOnce 36\end{configfileScr} 37 38As of v0.18.0, by default Stellarium tries to load HiPS from two sources: 39\url{http://alaskybis.unistra.fr/hipslist}\footnote{Since version 0.20.3 the first URL 40was changed to \url{http://alasky.u-strasbg.fr/MocServer/query?*/P/*&get=record} due to changes in HiPS services} and 41\url{https://data.stellarium.org/surveys/hipslist}. 42This can be changed with the hips/sources options in the configuration 43file (see also section~\ref{sec:config.ini:hips}). For example, you can add your 44own private HiPS surveys by running a local webserver and adding: 45 46\begin{configfile} 47[hips] 48sources/1/url = http://alasky.u-strasbg.fr/MocServer/query?*/P/*&get=record 49sources/2/url = https://data.stellarium.org/surveys/hipslist 50sources/3/url = http://localhost/Stellarium/hips/hipslist 51sources/size = 3 52\end{configfile} 53 54\section{Solar system HiPS survey} 55 56Though not specified in the HiPS standard, Stellarium recognises HiPS surveys 57representing planet textures, as opposed to sky surveys. If the 58\texttt{obs\_frame} property of a survey is set to the name of a planet or 59other solar system body, Stellarium will render it in place of the default 60texture used for the body. 61 62 63\section{Digitized Sky Survey 2 (TOAST Survey)} 64\sectionauthor*{Georg Zotti, Alexander Wolf} 65\label{sec:TOAST} 66 67The older way to provide a tessellated all-sky survey uses the TOAST 68encoding\footnote{Please see 69 \url{http://montage.ipac.caltech.edu/docs/WWT/} for details}. 70Stellarium provides access to the Digitized Sky Survey 2, a 71combination of high-resolution scans of red- and blue-sensitive 72photographic plates taken in 1983--2006 at Palomar Observatory and the 73Anglo-Australian Observatory.\footnote{The original data are available 74 at \url{https://archive.stsci.edu/cgi-bin/dss_form}.} 75 76To enable access to the DSS layer, see 77section~\ref{sec:gui:configuration:extras} and enable the DSS 78button. Then just press that DSS button in the lower button bar, wait 79a moment, zoom in and enjoy! 80 81\subsection{Local Installation} 82 83This display normally requires access to the Internet. However, in 84some situations like frequent and extensive use in fixed observatories, 85or use in the field when Internet connection is not possible, you can 86download all image tiles to your local harddisk for local use. Please be 87considerate, don't waste bandwidth, and do this only if you really need it. 88 89The images are stored in subdirectories that increase in size and 90number of files (see Table~\ref{tab:TOAST:levels}). Zooming in loads 91the next level if available. 92 93For partial downloads, you can limit the maximally used level (e.g. 9 94or 10). The difference from level 10 to 11 is really hardly 95noticeable, yet level 11 contains almost 75\% of all data. On a small 96system like Raspberry Pi 3, you may run into troubles with too little 97texture memory when level is more than 7. 98 99Another issue: the level 11 subdirectory holds over 4 million 100files. Windows \program{Explorer} is not optimized to open and display 101this number of files and will take a long time to open. Just unpack 102this archive, but don't access the folder with \program{Explorer}. 103 104If all that does not discourage you, you can download the archives at 105\url{https://dss.stellarium.org/offline/}. 106 107Then add a few entries to the \texttt{[astro]} section in 108Stellarium's \file{config.ini}. On Windows, if you have a harddisk 109\file{T:} with path \file{T:\textbackslash{}StelDSS} that contains the 110unpacked image subdirectories 0, 1, 2, \ldots, 10, the section may look like 111\begin{configfile} 112[astro] 113toast_survey_directory =StelDSS 114toast_survey_host=T:/ 115toast_survey_levels=10 116\end{configfile} 117On Linux, with the files stored in \file{/usr/local/share/Stellarium/StelDSS}, the same section could look like 118\begin{configfile} 119[astro] 120toast_survey_directory =usr/local/share/Stellarium/StelDSS 121toast_survey_host=/ 122toast_survey_levels=10 123\end{configfile} 124 125\begin{table}[htbp] 126 \centering 127\begin{tabular}{rrr} 128Level & No of files & Filespace (kB)\\ 1290 & 1 & 32\\ 1301 & 4 & 124\\ 1312 & 16 & 472\\ 1323 & 64 & 1.820\\ 1334 & 256 & 7.172\\ 1345 & 1.024 & 27.920\\ 1356 & 4.096 & 109.628\\ 1367 & 16.384 & 429.800\\ 1378 & 65.536 & 1.661.808\\ 1389 & 262.144 & 6.119.092\\ 13910 & 1.048.576 & 20.250.216\\ 14011 & 4.194.305 & 83.583.724 141\end{tabular} 142\caption{Number of files and storage requirements for local DSS TOAST installation} 143\label{tab:TOAST:levels} 144\end{table} 145 146 147 148 149%%% Local Variables: 150%%% mode: latex 151%%% TeX-master: "guide" 152%%% End: 153