I have a .ecw aerial image and one of the associated files is .prj, which i assume defines the Coordinate Reference System of the image. The .prj is as follows:
Which both here and here is described as EPSG:5551. Based on this I chose EPSG 5551 as the CRS of my QGIS project and made sure in settings that "When a new layer is created, or when a layer is loaded that has no CRS" QGIS "Use project CRS".
However, when i import my .ecw file, the project CRS is changed to EPSG 7855 (GDA2020 / MGA zone 55) and when i do right click on the layer and go to properties, i see that the layer's CRS is EPSG 7855. In other cases, another image's CRS changed to EPSG 28355.
I know that EPSG 5551, 7855 and 28355 are related, and all cover Zone 55 between Australia and Papua New Guinea. I want to understand why the CRS of my project is changing? Why the layer appears to have another CRS when i check its properties in QGIS? and if this may have a consequence in my project?