I have an SID raster and an mdb of shapefiles that at one point lined up in ArcMap but I cannot get them to line up anymore. They are both the same coordinate system - GCS NAD 1983. They won't even show up in the same frame together. I have to zoom to each to look at either of them. I have tried changing the coordinate systems and managed to get rid of the projected coordinate system on the shapefiles so that they are both just GCS NAD 1983 but to no avail. If anyone can help, I would appreciate it.
At this stage it is quicker if you have to right-click on each layer...go to properties, find the extent description.
It is highly likely that one or more of them have small numbers and some have large numbers.
That is the clue that one or more of the files has had its coordinate system defined wrong, because the Define Projection tool was used... this is the tool that people use incorrectly, when they want a file to BE something instead of telling it what it IS. If this tool has been used by you or anyone else, go back and define them back.
Should you want them in one coordinate system, use the Project tool once they are defined correctly
Exactly as Dan has said.
Define Projection tool should only be used when you have a dataset which does not have a SR or a wrong SR, and you know what it actually is. This can sometimes be deduced from inspecting the data extents and knowing where the data is supposed to be.
Once you have the data spatial reference defined correctly, only then can you use the Project tool to get all the data into a common system.
Once you have the files in their original projections, you can also set the dataframe projection to the projection of your choice and the files will be reprojected on the file, to the new projection. Then you can export the data and save them with the dataframe projection. I generally do this for the vector data versus the raster data.