Assigning CRS to a .shpfile and it disappearing

[jahillganvar]

I have a geodatabase polygon with a CRS WGS 1984, a LULC shapefile, and an aerial image both the later not having a specified CRS. I do know the CRS of the aerial image and I am suppose to project the both of the other layers in the aerial image CRS. I succeeded in overlaying the geodatabase polygon over the aerial image. But the LULC file keeps disappearing after I perform a Define Projection. It appears back when I do a Project analysis but the overlay is not happening. And when I try a project again it disappears and Zoom to Layer doesn't work.

Not sure what I am doing wrong. Should I create a new coordinate system for this?

[DanPatterson]

You don't use Define Projection unless the layer/file had an unknown coordinate system.  If you define one and it isn't in that coordinate system, it will be defined wrong and vanish.

If you want a file to BE in a different coordinate system, you have to Project it... this applies to both vector and raster data.

So if you have defined it wrong, define it back to what it was, then Project if needed.

An oldie...

Define Projection vs Project... a visual guide - Esri Community

[jahillganvar]

Yes, the shapefile has an unknown coordinate system.

[DanPatterson · Accepted solution]

Then define it.  It will either be correct and line up with other files, or it won't.  You can always define it correctly if you get it wrong the first time. 

Also.  You can delete the *.prj file of the shapefile using your operating system (eg File Explorer) Then you can get back to a truly "UNKNOWN" coordinate system

[jahillganvar]

Thanks it worked!!

[DanPatterson]

please close the thread by marking a response correct, so that others with the same problem will know there is a solution