[feature-request] Show a placeholder for images too far from the current observation date

[Patrick Schmiedel]

Currently, there is only one month of image data (October 2003), but as events are queried directly from the sources, they span a much bigger timespan. For dates sooner / later than oct. 03, the first / last picture for an image source is being used, which is completely different than the actual situation after a certain time (several hours).

I therefore suggest to display a "placeholder" image for dates for which there is no valid image in a given interval around the observation date. For images of the innermost "display group" (e.g. EIT), this could be just a yellow circle, for outer display groups, just empty tiles. Additionally (for all groups), a subtle text could be displayed, say something like "No INSTRUMENT/MEASUREMENT image available for YY-MM-DD hh:mm", similar to "no image available for this zoom level" on Google Maps.

This could be done in the TileStore class, however, I would like to see that implemented in the Helioviewer client, because any potential client should be able to decide on how to deal with such a situation.

[Jack Ireland (jack-ireland)]

In usage, we have taken the point of view of informing the user via the color of the time-stamp of the requested image if its observation time is distant from the requested time. It may be worthwhile to post a growl-like notification when the image request time is distant from the closest available image. This can be further subdivided into two different cases - the case when the instrument is known to be inactive (e.g., MDI, SXT) and the case when the instrument is active but for some reason we don't have an available image.

For example, let's say some requests an image from 2013-01-01 from SXT. The image is shown in the viewer window with two warnings

"Warning: the difference between the requested date/time and the closest available SXT image is large."
"Warning: Yohkoh/SXT ceased operations in December 2001."

Similarly, if someone requests AIA data from 1998, the viewer window would display the following warnings"

"Warning: the difference between the requested date/time and the closest available AIA image is large."
"Warning: SDO/AIA began operations in April 2010."

[Jack Ireland (jack-ireland)]

Same, or similar to bug #557355.

[Jeff Stys (jstys-z)]

Need additional information in order to implement.

1. What is the exact criteria for determining when a growl-like notification should be presented to the user? Is the criteria the same for all image data sources or do the time spans vary by observatory/measurement?

2. Need data set describing the known availability of each data source to encode into the API. How will this dataset be kept up-to-date for ongoing and future missions?

I would recommend toggling the visibility of the out-of-date layer to OFF whenever the imagery is grossly out-of-date. The growl-like notification would explain why this has occured and offer an option to the user to toggle it back On. This action would be an implicit aknowledgement that they understand the descrepancy between the requested time and the time of the displayed imagery.

[Jack Ireland (jack-ireland)]

Switching to invalid since this seems to not be a problem.