I've never joined photos to make one connected image, but I've taken rotating shots and put them together to show the various angles.
Taking the Pics:
this is obviously easiest if you have someone taking pics for you.
have them stand at the same location as you rotate, to get the same lighting.
pay attention to the distance from the camera to the tattoo - try to keep size and location consistent
if you're taking shots solo
set the camera on a level surface that frames your piece well
set the timer and take as many shots as your camera will do on timer
same as above - stand at the right distance from the camera and slowly rotate
take more shots that you need.
digital pics are free!
check out the set and redo as needed. be patient.
later, when you edit, you can choose the best ones that work well to show the piece as a whole
I've never tried this, but you might also be able to just take a video, then take stills from the video.
Editing the Pics
Choose the best shots that show a good rotation
Crop each shot at the same height locations of the tattoo - in this example, top of arm to bottom of half sleeve
Resize each image to be the same height
Adjust values of each image, to be as consistent as possible
Save
Open a blank file and insert each shot in the rotation
Align to fit
Crop if needed
Adjust values as a whole rotated image, if needed
This is pretty amateur, but it's good enough for my needs.I've got nothing on ATAK. If you haven't already, check out Bloodwork: Sleeves and Bodies.
Hope this helps!