How effective are blow up decoys as shown in the PLA Pictures thread?
Well here's something I have to add. It is effective in visual photos... the ones that rely on visible light. However, once you go into other bands, it becomes different because metal and wood tends give off very different signatures than the canvas or plastic of the decoy.
So it would fool photographs, but wouldn't fool multi-spectral images.

Modern artillay and mortar rounds are able to "see" the difference.

Yes, but that ties your assets and mostly I think they'd use them beyond your artillery range.

Beyond? Artillary can be moved.

And that means repositioning arty that could be used elsewhere... elsewhere where there are actual enemy troops.
And tactically this little reorganization on your part could give the enemy the temporary advantage it needs.

Hence the use of DECOYS

Yup.

He got you there 13th redneck.

Decoys are effective.
Either way we learn together this way.

Decoys are a great way to divert attention from the real massing of troops. Look at the examples from WWII. D-Day preparations etc etc, the use of plywood tanks, planes, trucks etc.

And during WW1 the use of tramp steamers with wooden cannons mounted on deck to give a more menacing presence to the merchant navy convoys. The more "guns" the enemy sees, the more likely they are to reconsider a fool hardy attack.