Yes, if you want to compare them they'll need to be in the same coordinate system.

You can use the Reprojector to force both sources into the same coordinate system.

Hi again, @Hans van der Maarel​ @aron​ 

I should have said the TIFF file is as refrence file, so, even if it was refrence file, I should have convert it to another coordinate syatem?, I attached the propertise about TIFF and SHP file.

These two are the same. If that is the case, you won't need to reproject anything.

As a rule of thumb: as soon as you want to make any kind of geographical analysis between two datasets in FME you need to make sure they are in the same coordinate system, FME is not going to do that for you.

Thank you so much for your help @Hans van der Maarel​ 

I also have another question. I have two TIFF with different resolution. So, I want to know , What resolution do I choose to measure the differences between the DTMs?

It depends, I guess. Is interpolation acceptable or not (and if so, how much)? Can you tell us a bit more about your application?

Yes, Thank you. This is a student project.

Could you please give me another clue, about How we can understand the unit of DTM is meter or feet?, in properties there is not any information about Linear unit, and only have angular unit.

I kinda thought it was a student project 😅

Really something like this should be documented. If it isn't you can try doing a sanity check on the data. For elevation, see if you can find out from another source what the elevations for that area are and then compare it to your data.

Are there any clues in the file names? The DTM I use always have "_2m" or something similar in the name. Or go back to where you collected them, whoever shared them would know what they are.

@Hans van der Maarel​ I compare that with google earth and got it. Thank you so much for your help.

@aron​ Thank you for your help.