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Documentation Advanced Search

Advanced Search

Advanced Search is a browser interface to all the data collections stored at CADC. Queries can be constrained by a wide variety of metadata including observation details, position, time and energy. The Results table returned by queries can be filtered and sorted to further refine search criteria. The Results table contains links for data download, previewing of data, full results table download, viewing more information on the observation and execution of related queries.

Basic usage

You can log in with your CADC username and password. This provides authenticated access that allows you to discover files that have protected metadata and download files that have protected data. Your username must be a member of the relevant group for proprietary access to be granted.

Advanced Search uses separate tabs for Search and Results, enabling you to switch from one to the other to modify the query.

Search tab

An image of the Search tab is shown below. The upper portion of the tab contains mostly text/numeric boxes, whereas the lower portion contains a clickable Additional Constraints section.

  • You can use wildcards (*) in text based searches, and inequalities (< and >) and ranges (..) in numeric searches.
  • The P.I. Name, Proposal ID and Proposal Title fields have an autocomplete function based on values stored in the database.
  • The Target can be the observer-specified target name or a resolved target name or position coordinates.
  • The Additional Constraints section is dynamic from left-to-right, limiting the latter options based on the available archive content.
Advanced Search query tab

In this example the query is constrained by the Observation ID, the resolved target position, the observation date and the collection. You can click on the question mark icon next to each field for an explanation of the field and examples.

Results tab

The Results tab for the above query is shown below.

Advanced Search results tab
  • You can download data by marking rows and hitting the Download button or by clicking on the direct download icon in the Mark column.
  • Mouse over the Preview link to see a thumbnail of the data or click to get a full page preview.
  • Click on the Obs. ID or Product ID links to open a page with detailed information on the observation. This page shows the data model structure of the observation. For more details on the data model see the CAOM2 documentation (where is this to be stored?)
  • Click on fields such as Start Date, Target Name, Proposal ID and P.I. Name to launch another query on these parameters.
  • There is a limit of 30,000 on the maximum number of rows displayed in the results table. You can download a table with the full results of the query by clicking on one of the VOTable, CSV or TSV links.

Advanced usage

You can add a string to the Advanced Search URL to pre-populate some fields in the Search tab. The structure of the URL strings are based on the ADQL query syntax (see below). For example, to perform a query for processed (Calibration Level=2) SCUBA-2 data from JCMT, use

http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/search/?collection=JCMT&Observation.instrument.name=SCUBA-2&Plane.calibrationLevel=2&noexec=true

There are two/three additional tabs on the Advanced Search page:
  • Error displays on error message when there is a problem with the query
  • ADQL stands for Astronomical Data Query Language (similar to SQL) and this tab displays the query syntax that you can copy to perform command-line queries using the Table Access Protocol (link to TAP doc?)
  • Help tab - I suggest we remove it.

Search tab

The Target box allows three methods of constraining the target of the observation:

  • Spatial coordinates in either Equatorial or Galactic coordinates in degrees or sexagesimal.
  • Target Name match in the database. This option is selected by clicking on None (Target Name match) in the Resolve with selector. Note that observers have a range of naming conventions so this method is not guaranteed to find all observations of a particular object.
  • Resolved position. This option is selected by clicking on Automatic (Recommended) or SIMBAD or NED or VIZIER in the Resolve with selector. If the target resolving is successful a green tick appears to the right of the text box and a window pops up on the left side with information about the resolved target (see screenshot below).

Target resolving display

For Spatial coordinate and Resolved position searches a radius can be appended to search over a specified area surrounding the target. If not specified, a default radius of 1 arcminute is applied.

For multiple target queries a file can be uploaded with the Choose File button. Each line of the file should contain one target name to be resolved or one position in the same format as required for the Target text box. Click on the eraser icon to remove the target file.

To avoid having to download entire large data files or to obtain a series of data all at a consistent pointing or energy centre, it is possible to do data cutouts by selecting the Do Spatial Cutout or Do Spectral Cutout checkboxes. For Spatial Cutouts the image will have a diameter twice the radius specified in the Target box. For Spectral Cutouts the Spectral Coverage box must contain the spectral range, with values separated by '..'. Note that not all spectral data at the CADC support spectral cutouts.

Results tab

A powerful feature of Advanced Search is the ability to continue to refine queries and reorganise results on the Results tab using filtering, sorting, unit conversion and column configuration.

  • The results table can be filtered by entering text on the "Filter:" row. String columns are filtered using substring matching. Numeric columns can be filtered with inequalities and ranges. When text is entered in the "Filter:" row an autocomplete pop-up box appears with values that can be selected.
  • The results table can be sorted by clicking on any column header. Click again to reverse the order.
  • Fields with units have a unit conversion functionality so you can choose the units most convenient for the type of data. Unit selection is done by clicking on the labelled unit selectors underneath the "Filter:" row. Note that the filtering action depends on the selected units.
  • You can customize the columns. There are too many fields in the database for each observation to fit on the screen. Only a subset of all columns is displayed in the table by default and there is a horizontal scrollbar to facilitate viewing these columns. It is also possible to choose which columns get displayed and the ordering of the columns. The width of each column can be adjusted by dragging the boundary between column headings. Columns can be moved by dragging column headings. More detailed customization can be done with the pop-up that appears when the Change Columns button is clicked. Drag fields from right to left (left to right) or click on the checkbox to make them visible (hidden) in the table. Sort the field names alphabetically using the up-down arrow buttons. The extra buttons at the top of the Change Columns pop-up will display all columns or go back to the default columns.

Contact CADC for Assistance

For help and support with Advanced Search, please email cadc@nrc.ca