At the March 2018 DM-SE mini-JTM, there was a session "DM/SE visualization discussion for commissioning". As it turned out, an hour of the session ranged rather widely across visualization use cases across the whole of development, commissioning, and early operations.
Below is a list of the use cases, transcribed from the whiteboards in the meeting room. In the coming days the intent is to expand on these use cases by adding information that clarifies the use cases, describes whether they are pure visualization requirements or involve LSST-specific analytics, and how these might be - or already are - addressed by the Science Platform SUIT components or by other libraries or systems (e.g., matplotlib, Bokeh).
Priorities in the last two columns are keyed as follows: 1 – Critical, 2 – Nice to have, 3 – Optional.
| No. | Use case key topic (from original whiteboard) | Initial clarification | Commmissioning Priority | DM Priority |
|---|---|---|---|---|
| 1 | Visualization of all-sky "stuff" (a/k/a statistics, e.g., MAF metrics) | This is the display of quantities that are evaluated across the entire (LSST-observed) sky and are desirable to be able to explore at a range of scales from all-sky down to the finest-grained level at which they are defined. KB: This becomes more important with LSSTCam and particularly the SV surveys when we start having larger contiguous regions of sky coverage. | KB: 1 | |
| 2 | Collections of thumbnails | Meant to be around a designated set of objects or sources (if sources, this could be a time-dependent selection of apparitions of the same object). | KB: 1 | |
| 3 | Brushing and linking between scatter plots and thumbnails | Could mean: use brushing and linking to select the sources around which to request thumbnails, or: use brushing and linking to narrow the displayed set of thumbnails from an already-requested set. | KB: 2 | |
| 4 | Extensible displays | Because the set of interesting specific visualizations far exceeds what could be provided centrally, make it possible for users to define visualizations, constructed from the lower-level visualization capabilities in the system (or an external library), in a way that makes them straightforward to apply on demand. | ||
| 5 | Turn on and off sources based on flags (i.e. with checkboxes) | These flag selections are meant to participate in whatever more general brushing and linking environments are provided - e.g., to permit sources/objects with designated flags to be shown or hidden in, say, a color-color plot or in an overlay over an image. | ||
| 6 | Quick access to schema descriptions | (Gregory Dubois-Felsmann doesn't remember exactly what was meant when this was raised in the meeting; the following is a guess.) | ||
| 7 | "Standard" image interactions in a responsive way: scale, stretch, zoom, pan, colormap | There was a general desire for stretch/scale changes to be "fast". CFC: This needs to include interactive hierarchical capabilities - e.g. display of a full FOV image consisting of 21 science rafts + 4 corner rafts in some definable spatial compression/sampling scheme (e.g. box average, max value, median filter etc..) to make the full FOV image manageable. Interactive feature need to include selecting a specific science or corner raft for more detailed display, followed by selecting a given sensor on a raft for pixel level display and computational (IRAF imexamine like) operations. | CFC: 1+++ KB: 1 | |
| 8 | On-demand pixel-level colorized images | Generation RGB color images based on the combination of three single-channel images (at a minimum: single-channel images with precise registration with each other, but it need not be limited to this). Both the "traditional" and the "hue-preserving" algorithms should be supported. | ||
| 9 | Colorized overlays on greyscale images (with tunable alpha) | This refers to the rendering of single-channel image data with a hue or a partially transparent color overlay based on an additional channel (e.g., colorizing a single-channel flux image by the per-pixel variance). Note that mask-overlay display could be treated as an instance of such a capability, but for tracking purposes we'll treat it separately. | ||
| 10 | Crossfading between images | Using a slider, allow the continuous variation of what is displayed based on two over-plotted images of the same region (whether in sky or x-y coordinates), moving from displaying one or the other image through displaying a superposition of the two. Alternatively, using a slider or a movable "curtain" UI element to wipe one image across the other. | ||
| 11 | Graphical instrument navigation | Display of mosaics of image data from the focal plane, or other data displayed in focal plane coordinates, with UI elements that make the components of the Camera assembly hierarchy (rafts, 3-CCD sets associated with a REB, CCDs, and amplifier segments) selectable. It is desired for that selection to then be usable to control other behaviors of visualizations, e.g., limiting displays of the DIASources from a visit to those detected on the selected subset of the focal plane. | ||
| 12 | Full focal plane visualization
| The "?" represents an initial pass of the discussion in which we decided not to drill down into what it really means to display a full FP image as a whole on a screen (given the ~3 orders of magnitude of summarization required). As a matter of implementation, the people in the room were open to doing this as an application of HiPS. In some cases this is a bit of a creative misuse of HiPS, which is sky-coordinate-oriented, but this seems to still be a meaningful and useful operation. More discussion, and perhaps a demonstration, would be appropriate. (On-sky images could be converted to HiPS mapped onto their actual pointing on the sky; other images (e.g., flats) could be mapped to a pro-forma pointing in the HEALPix grid.) CFC: Displaying the full FOV image in the contest of the surrounding sky would be very useful in commissioning - what are the neighboring bright source with respect to the displayed image? | KB: 1 CFC: +1 | |
| 13 | All the things in focal plane (image, variance, bad pixel masks etc...) | CFC: These need to have a toggle function for visibility and many variable transparency too. | KB: 1 CFC +1 | |
| 14 | Summarized full focal plane images | Precomputed full-focal-plane images might be made available based on standard aggregation functions, e.g., mean, median, max, or stretched to show noise. Other aggregation functions should be available on-demand, including ones implemented as callbacks to user (Python) code. (Noting that a full summarization of a 3-gigapixel image down to the O(1 megapixel) images suitable for screen display may be time-consuming.) KB: pandas has some nice grouping and aggregation functionality that would certainly be useful. This might be more of data analysis than visualization directly, but in any case, I think we definitely want this functionality and a visualization wrapper pandas might get most of the way there. | ||
| 15 | Display of image backgrounds (pixels, models, and residuals) | Also may want to compare to other properties of catalogs and perhaps PSF models etc. | ||
| 16 | Display of LSST data objects with natural on-image interpretations: (Heavy)Footprints, PSF models at a point, PSF variation models or measurements | Footprints should be clickable to facilitate investigation into deblending computations. | ||
| 17 | Vector field plots (e.g., astrometric residuals,PSF moments or other technical information from the EFD) | The scale factor must be adjustable. KB: matplotlib quiver plots, for example? We definitely need something along those lines for astrometric residuals and PSF characterization | CFC +1 KB: 1 | |
| 18 | Per-source drill down | Select a source/object (in a table, over plotted on an image, in an x-y plot) and be able to link to additional visualizations or data displays related to that source/object/ | ||
| 19 | Individual mask planes (including: across a full focal plane; for coadds) | "Individual" apparently meaning that one or more mask planes to be displayed could be selected programmatically or by UI, with flexible assignment of colors and transparency. | ||
| 20 | Brushing and linking | Across images, histograms, and scatterplots (on the board these pairs of those were called out: image-hist, image-scatter, hist-scatter, but hist-hist, scatter-scatter, and so on also make sense). Support pairwise scatterplots (e.g., displays of the matrix of all x-y plots derivable from a set of N variables). | CFC +1 | |
| 21 | Chips and optics
| E.g., display mean per-chip offsets, from an astrometric analysis, relative to the nominal or previously computed positions of the chips. | ||
| 22 | Flip books per source | Understood to be temporal in nature. Display of image cutout flip books for selected sources. Automatic definition of default cutout dimensions based on source properties (e.g., smaller for point like sources, larger for extended sources, perhaps including the full parent footprint for deblended sources). Flip books for (raw, calibrated, etc.) flux images; for source models computed for each epoch; for residuals (e.g. from difference imaging vs. templates, or image-to-model residuals, where the model could be per-epoch or time-integrated). | ||
| 23 | Mean color residuals for single epochs projected into CCD coordinates and integrated over many stars (with or without nominal photometric corrections) | This is the photometric analog of the well-known DES focal-plane astrometric residual display. | ||
| 24 | Instrument footprint on all sky (or all-sky) images | This could mean both:
| ||
| 25 | Overlay R90 Petrosian ellipses on images for selected sources | Or any other spatial visualizations of the source/object models. This could include display of the fitted parallax and proper motion model for a Milky Way object, with time ticks corresponding to observation epochs. | ||
| 26 | gri offsets (sky) from coadds with drill down to single epoch gri | Including image on chip scale, PSF models. | ||
| 27 | Coding of (X-Y plot or image catalog overlay) points by color, size, shape by 3rd variable, in spatial projections (CCD, sky, etc.) | Really applies to any x-y plot, not just spatial plots. | ||
| 28 | Plot source density maps Example: density of (DIA)Sources compared to sky brightness (e.g., colormap and contour) | (further clarification of the "colormap and contour" would be helpful) |