Changes between Initial Version and Version 1 of TargetLocation


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Timestamp:
06/09/05 12:19:42 (17 years ago)
Author:
rick
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  • TargetLocation

    v1 v1  
     1Note -- need to clean up HTML encoded entities.  -- Joe 
     2 
     3== Target Location == 
     4 
     5Target location, by which is meant the spatial location of the target 
     6region of imaged or pointed observations on or around the Sun or in 
     7the heliosphere, has not yet been built into any VSO query models, 
     8although it is a fairly natural selection criterion for observations 
     9with a restricted field of view.  It may suffice to specify a simple 
     10uniform description, although the multi-dimensionality of space makes 
     11this harder than one for time.  For two-dimensional image data we assume 
     12a bounding circle as the simplest model.  For this model it is sufficient 
     13to specify the center location and radius of the bounding circle. 
     14Most real image data are actually described by a bounding rectangle, 
     15but this requires specifying at least five parameters (''e.g.'' 
     16the coordinates of opposite corners and a position angle).   
     17 
     18 
     19==== Observation_Center_West ==== 
     20 
     21 
     22  type: ''number''[[BR]] 
     23  unit: ''arc-second''[[BR]] 
     24  FITS keyword: ''CENT_WST'' 
     25 
     26==== Observation_Center_North ==== 
     27 
     28 
     29  type: ''number''[[BR]] 
     30  unit: ''arc-second''[[BR]] 
     31  FITS keyword: ''CENT_NRT'' 
     32 
     33  A pair of coordinates specifying the location of the center of the 
     34image data circle with respect to the Earth-Sun line at the nominal 
     35Observation_Time.  This origin is close to the center of 
     36the apparent solar image for Earth-based or near-Earth observers, but 
     37not necessarily for deep space observations.  The North coordinate 
     38is measured in the direction of the Carrington axis (RA 286 °13, 
     39δ 63°.87 J2000.0), and the West coordinate in the direction 
     40of solar rotation. 
     41 
     42 
     43==== Bounding_Radius ==== 
     44 
     45 
     46  type: ''number''[[BR]] 
     47  unit: ''arc-second''[[BR]] 
     48  FITS keyword: ''R_BOUND''[[BR]] 
     49 
     50  The radius of the bounding circle about the Observation_Center. 
     51For the VSO Data Model the bounding circle is to be understood as either 
     52the maximum inscribed circle in the bounding data rectangle (polygon), 
     53or the minimum circumscribed circle, depending on whether the query is 
     54for included data (presumably the normal default) or excluded data, 
     55respectively.