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diff --git a/funtools/doc/regcoords.html b/funtools/doc/regcoords.html deleted file mode 100644 index ff656c2..0000000 --- a/funtools/doc/regcoords.html +++ /dev/null @@ -1,239 +0,0 @@ -<!-- =defdoc regcoords regcoords n --> -<HTML> -<HEAD> -<TITLE>Spatial Region Coordinates</TITLE> -</HEAD> -<BODY> - -<!-- =section regcoords NAME --> -<H2><A NAME="regcoords">RegCoords: Spatial Region Coordinates</A></H2> - -<!-- =section regcoords SYNOPSIS --> -<H2>Summary</H2> -<P> -This document describes the specification of coordinate systems, and the -interpretation of coordinate values, for spatial region filtering. - -<!-- =section regcoords DESCRIPTION --> -<H2>Pixel coordinate systems</H2> -<P> -The default coordinate system for regions is PHYSICAL, which means -that region position and size values are taken from the original -data. (Note that this is a change from the original IRAF/PROS -implementation, in which the IMAGE coordinate system was the default.) -PHYSICAL coordinates always refer to pixel positions on the original -image (using IRAF LTM and LTV keywords). With PHYSICAL coordinates, -if a set of coordinates specifies the position of an object in an -original FITS file, the same coordinates will specify the same object -in any FITS derived from the original. Physical coordinates are -invariant with blocking of FITS files or taking sections of images, -even when a blocked section is written to a new file. - -<P> -Thus, although a value in pixels refers, by default, to the PHYSICAL -coordinate system, you may specify that position values refer to the -image coordinate system using the <B>global</B> or <B>local</B> -properties commands: - -<PRE> - global coordsys image - circle 512 512 100 -</PRE> - -The <B>global</B> command changes the coordinate system for all -regions that follow, while the <B>local</B> command changes the -coordinate system only for the region immediately following: -<PRE> - local coordsys image - circle 512 512 100 - circle 1024 1024 200 -</PRE> -This changes the coordinate system only for the region that follows. -In the above example, the second region uses the global coordinate -system (PHYSICAL by default). - -<P> -<H2>World Coordinate Systems</H2> - -If World Coordinate System information is contained in the data file -being filtered, it also is possible to define regions using a sky -coordinate system. Supported systems include: - -<PRE> - name description - ---- ----------- - PHYSICAL pixel coords of original file using LTM/LTV - IMAGE pixel coords of current file - FK4, B1950 sky coordinate systems - FK5, J2000 sky coordinate systems - GALACTIC sky coordinate systems - ECLIPTIC sky coordinate systems - ICRS currently same as J2000 - LINEAR linear wcs as defined in file -</PRE> - -In addition, two mosaic coordinate systems have been defined that -utilize the (evolving) IRAF mosaic keywords: - -<PRE> - name description - ---- ----------- - AMPLIFIER mosaic coords of original file using ATM/ATV - DETECTOR mosaic coords of original file using DTM/DTV -</PRE> -Again, to use one of these coordinate systems, the <B>global</B> or -<B>local</B> properties commands are used: - -<PRE> - global coordsys galactic -</PRE> - -<H2>WCS Positions and Sizes</H2> - -In addition to pixels, positional values in a WCS-enabled region can -be specified using sexagesimal or degrees format: - -<PRE> - position arguments description - ------------------ ----------- - [num] context-dependent (see below) - [num]d degrees - [num]r radians - [num]p physical pixels - [num]i image pixels - [num]:[num]:[num] hms for 'odd' position arguments - [num]:[num]:[num] dms for 'even' position arguments - [num]h[num]m[num]s explicit hms - [num]d[num]m[num]s explicit dms -</PRE> - -If ':' is used as sexagesimal separator, the value is considered to be -specifying hours/minutes/seconds if it is the first argument of a -positional pair, and degrees/minutes/seconds for the second argument -of a pair (except for galactic coordinates, which always use degrees): - -<PRE> - argument description - ----------- ----------- - 10:20:30.0 10 hours, 20 minutes, 30 seconds for 1st positional argument - 10 degrees, 20 minutes, 30 seconds for 2nd positional argument - 10h20m30.0 10 hours, 20 minutes, 30 seconds - 10d20m30.0 10 degrees, 20 minutes, 30 seconds - 10.20d 10.2 degrees -</PRE> - -Similarly, the units of size values are defined by the formating -character(s) attached to a number: - -<PRE> - size arguments description - -------------- ----------- - [num] context-dependent (see below) - [num]" arc seconds - [num]' arc minutes - [num]d degrees - [num]r radians - [num]p physical pixels - [num]i image pixels -</PRE> - -For example: -<PRE> - argument description - ----------- ----------- - 10 ten pixels - 10' ten minutes of arc - 10" ten seconds of arc - 10d ten degrees - 10p ten pixels - 0.5r half of a radian -</PRE> - -<P> -An example of using sky coordinate systems follows: - -<PRE> - global coordsys B1950 - -box 175.54d 20.01156d 10' 10' - local coordsys J2000 - pie 179.57d 22.4d 0 360 n=4 && annulus 179.57d 22.4d 3' 24' n=5 -</PRE> - -At the FK4 1950 coordinates 175.54d RA, 20.01156d DEC exclude a 10 -minute by 10 minute box. Then at the FK5 2000 coordinates 179.57d RA -22.4d DEC draw a radial profile regions pattern with 4 quadrants and 5 -annuli ranging from 3 minutes to 24 minutes in diameter. In this -example, the default coordinate system is overridden by the commands -in the regions spec. - -<H2>NB: The Meaning of Pure Numbers Are Context Sensitive</H2> - -<P> -When a "pure number" (i.e. one without a format directive such as 'd' -for 'degrees') is specified as a position or size, its interpretation -depends on the context defined by the 'coordsys' keyword. In general, -the rule is: - -<P> -<B>All pure numbers have implied units corresponding to the current -coordinate system.</B> - -<P> -If no coordinate system is explicitly specified, the default system is -implicitly assumed to be PHYSICAL. In practice this means that for -IMAGE and PHYSICAL systems, pure numbers are pixels. Otherwise, -for all systems other than LINEAR, pure numbers are degrees. For -LINEAR systems, pure numbers are in the units of the linear system. -This rule covers both positions and sizes. - -<P> -As a corollary, when a sky-formatted number is used with the IMAGE -or PHYSICAL coordinate system (which includes the default case of no -coordsys being specified), the formatted number is assumed to be in -the units of the WCS contained in the current file. If no sky WCS is -specified, an error results. - -<P> -Examples: - -<PRE> - circle(512,512,10) - ellipse 202.44382d 47.181656d 0.01d 0.02d -</PRE> - -<P> -In the absence of a specified coordinate system, the circle uses the -default PHYSICAL units of pixels, while the ellipse explicitly uses degrees, -presumably to go with the WCS in the current file. - -<PRE> - global coordsys=fk5 - global color=green font="system 10 normal" - circle 202.44382 47.181656 0.01 - circle 202.44382 47.181656 10p - ellipse(512p,512p,10p,15p,20) -</PRE> - - -<P> -Here, the circles use the FK5 units of degrees (except for the -explicit use of pixels in the second radius), while the ellipse -explicitly specifies pixels. The ellipse angle is in degrees. - -<P> -Note that Chandra data format appears to use "coordsys=physical" -implicitly. Therefore, for most Chandra applications, valid regions -can be generated safely by asking ds9 to save/display regions in -pixels using the PHYSICAL coordsys. - -<!-- =section regcoords SEE ALSO --> -<!-- =text See funtools(n) for a list of Funtools help pages --> -<!-- =stop --> - -<P> -<A HREF="./help.html">Go to Funtools Help Index</A> - -<H5>Last updated: November 17, 2005</H5> - -</BODY> -</HTML> |