Hi all.
I meant to post this several weeks ago when I discovered this issue, but hadn't got all the supporting documentation together. I thought I'd do it now while I have the information and a chance to post it.
It is specifically to do with QGIS 3.40 (seems to have been fixed in QGIS 3.44), so is probably not so relevant now, but I could find any information in this forum or on the web relating to this issue (not to say that it doesn't exist, I just couldn't find aything :-) ), so thought it worth noting in here in case someone somewhere experiences the same issue.
It is to do with very unusual behaviour I noticed when re-projecting on-the-fly a WGS84 (EPSG 4326) layer onto a MGA2020 (EPSG 7849-7856) project.
So in QGIS 3.40 I had a project that was set to have its over-arching CRS as MGA2020 Zone 50 (EPSG 7850).
I brought in a point layer in which was using WGS84 coordinates (EPSG 4326).
It displayed the points fine in the map....
...however as soon as the re-projection method was requested in QGIS, e.g., when going to layer properties....you know, this dialog below.....
(which I find incredibly useful by the way)
...and the relevant method chosen, the points would mysteriously disappear from the map view. They would still be there, it's just that they would not display. For example, using the "Identify Features" tool would select one of the points and display the corresponding information in the "Identify Results" panel. So it knew there was something there, it just wouldn't display it.
Even more confusingly, when right-clicking the layer and going to "Zoom to Layer(s)", it would zoom to the coordinates as if the long/lat values were the easting/northing values, e.g., easting 115.72 northing -32.91. There was not anything there, but it would think that's where the points were.
And that was it - as soon as the points disappeared from the map, they were gone and you could not see them.
It was doing my head in and I spent hours troubleshooting this (for someone else's QGIS project I should add) when I thought I would install QGIS 3.44 and do the exact same thing and see what happens. I was very thankful to discover that everything worked as it should, and the points displayed in the map no problem, and stayed there after choosing the desired re-projection method. Hooray! (NB: Works fine in QGIS 4.0 as well).
So, I know this is not that current, as I expect most people are using QGIS 3.44 or later, where re-projecting a WGS84 layer to a MGA2020 project is not an issue, but I wanted to share these findings on the off chance there are some QGIS 3.40 users out there who might experience this same behaviour, and try searching for information on it, and hopefully discover the work-around here, and save them some time.
Just one of those oddities you hit every now and then. I hope it helps someone :-)
Have a good weekend.
Regards,
Drew
