10 Line identifications in Specview

10.1 Getting started

The Line Identification Tool provides the means for reading line identifications from tables (henceforth called line lists) and drawing them on the Specview plot surface. Line identifications can also be saved to text files. The final products of the tool consist of both spectral plots with the line identifications marked on them, and text files with the line identifications.

 

Specview contains a prototype interface to Simple Line Access Protocol (SLAP) servers. These servers are automatically queried when the Line Identification Tool is first invoked and thus require no user intervention.

 

At this point, there is no provision for automatically matching line identifications with actual spectral features.

 

The line identification tool is invoked by clicking on the “L” button at the upper right in the plotting window:

 

 

The button causes the tool to display its user interface and get ready for use.

 

At the same time, several selectors in the main Specview window are grayed out to prevent the displayed spectral data to be replaced by something else. The affected selectors are activated back when the line identification tool is dismissed by the Dismiss button in its user interface.

 

The user interface consists of a main control panel subdivided into several controls. It looks somewhat like this:

 

 

 

 

The basic operation consists in selecting one or more entries in the displayed table (by clicking the mouse over them, either alone or accompanied by either the Shift or Ctrl keys), and hitting the Draw button. This causes the selected entries to generate annotations on the plot surface, more or less like this:

 

 

 

 

Note: of course, the line identifications will only match spectral features if the spectrogram is displayed on a rest wavelength scale. See Sec. 4.3 on how to do that.

 

10.2 The annotations

The generated annotations are full-fledged screen objects that can individually be edited, repositioned and modified to suit the user’s tastes. A more complete description of these annotations capabilities is given in Sec 2.6.

 

The annotations generated by the line identification tool have an important difference with respect the general-purpose annotations described in Sec. 2.6. It is related to the way the line identification annotations position themselves on screen. Instead of either using the screen coordinates or the WCS coordinates to position themselves in both the X and Y axis, they work in mixed mode. In this mode, the WCS coordinates are used in the X direction, while screen coordinates are used in the Y direction.

 

By obvious reasons, the line identification annotations cannot be dragged in the X direction. Dragging a line identification annotation causes it to move up and down only.

 

10.3 The control panel

The control panel is comprised of multiple sub-panels. In the paragraphs below, each one is discussed individually.

 

 

10.3.1 Line list selectors

 

The tabs at the top give access to multiple line lists. These line lists are taken from a library of line lists. Details about the library and how the user can add his/her own line lists to the library are discussed in Sec. 10.5.

 

The tool tip display (hold the mouse over a tab for one sec.) displays more information about the corresponding list, usually its title and wavelength range.

 

Clicking on a tab brings the user interface for that specific line list to the screen. It does not mean that the other lists are disabled or inactive. Selections and customizations made on each list are always active and used for all operations. The tabbed window mechanism is just a way of optimizing screen real state.

 

Not all line lists present in the library will show up however. Tabs are created only for line lists that have a common wavelength range with the spectrogram being displayed.

 

Note: if the list is not available locally, a panel with a Download button shows up instead. Click on the Download button to get the list.  Once downloaded, a list remains locally accessible for the life of the application. See Sec. 10.5 on how to get those lists locally in a more permanent way.

 

 

10.3.2 Line list identification

 

The Line list field displays the identification info for the specific line list being displayed. This field is populated from meta information stored in the line list library. See Sec. 10.5 for details.

 

 

10.3.3 Line sets

 

Each line list can generate multiple, identical sets of line identifications. The Set tabs work together with the Add set button at the bottom to enable the user to create new line sets from a single line identification list, and select one of them for display. Each line set holds an identical copy of the line identifications present in the corresponding list, but line identifications can be selected independently in each set.

 

Line sets are useful in circumstances in which one wants to use a single line list but at the same time wants to handle different parts of the list in different ways. For example, one may want to depict line identifications of forbidden lines with a different color than line identifications of permitted lines, but at the same time wants all the identifications to be generated from a single line list.  One would in this case click the Add set button once to generate a Set 2 line set. Then in the Set 1 set one selects, say, the permitted lines, while in the Set 2 the forbidden lines are selected. When the Draw button is clicked on, line identifications will be taken from both sets and displayed on the plot surface.

 

 

10.3.4 Table

 

The table displays data taken directly from the line identification list. Its format and contents are list dependent and partially governed by the meta information associated with the corresponding line list. See Sec. 10.5 for information on how to control the table format.

 

The table may not display the entire contents of a line list. It displays only line identifications that can be associated with the current spectrogram, namely, line identifications whose wavelength / frequency / energy fall within the range of the spectrogram.

 

Fields in each column are displayed “as is” from the original line list. For instance, no formatting is applied to numerical fields, so they displayed field can be directly compared with the original.

 

10.3.4.1 Sorting the table

 

The table supports hierarchical sorting on each column. Clicking the column header successively cycles the sorting status of the corresponding column among the states: unsorted, sorted in ascending order, sorted in descending order. The column header will display a little triangle that encodes the sorting status of the column.

 

By holding the Ctrl key down while clicking on the column header, the sorting status of previously sorted columns is kept unchanged, thus allowing hierarchical sorts. This feature, coupled with the line sets capability (Sec. 10.3.3), is sufficient to enable relatively complex selections to be drawn from a line list, without resorting to any other kind of filter.

 

10.3.4.2 Selecting identifications from the table

 

Individual line identifications are selected by just clicking the mouse over them. By holding either the Shift or the Ctrl keys down while selecting rows on the table, multiple selections of adjacent or disjoint line identifications can be done as well.

 

The Select all button automatically selects all lines present in the line set. The Unselect all button does the opposite effect. Note that both buttons act only on the respective line set (the one being displayed).

 

10.3.4.3 Total line count

 

The numerical field at the lower left corner displays a current count of the total number of selected line identifications. When this total count exceeds 1000, it is displayed in red to remind that the drawing operation may become significantly slow from that point on.

 

10.3.5 Graphics properties

 

Two graphics properties of the annotations associated with a given line set can be controlled by the user:

 

 

Bug: under some circumstances, the frame around the plot may not display properly. See Sec. 2.6 for more details.

 

 

10.3.6 Drawing and erasing

 

The Draw and Erase buttons always act on the entire set of annotations selected in all line sets and all available line lists.

 

These buttons should be used to fix problems in the identifications layout if one seeks aesthetically pleasing plots. Usually by playing with the plot zoom functions, window resizing, placement on screen, and individual annotation placement, one can achieve satisfactory results in most cases.

10.4 Saving results to file

The selected line identifications can be at any time saved to text files using the Save and Save as functions in the File menu in the line identification tool control panel.