Well as it is written a sconce is filed fort made of earth of high profile, and it is a defensive weapon...They learned to build them in Austrian freikorps or freikor where some of them served as officer during Frontier Rebelion...Since hill was near river Sava it was on frontier of Austrian empire...Turks send message to people across river to come and watch the battle...Austrian officers raised a watch post on both banks, so they could inform about the battles...
Funny thing is that in every battle there was at least one sconce...There are many of them that survived the time, but small amount of those that survived was in major battles...One of them is in local village...It is in form of square...He is covered by tall grass, but it would be wise to buy the place from peasant and make it as tourist attraction...
There also was one fortress with great complexity called Deligrad or hero town, it was a complex of sconces made in shape of triangle...In that place there are still some palisade left...Here is photo...
Now here is illustration how usually battles would look like...
Now concerning size, it is an old measurment, not the English foot, but local foot measurment...It is said that it has between 1 and 2 meters, not sure how much, something about 165 cmm, now maybe I am telling stupid things, but in literature it is said that that sconce had sides of 280 meters and 300 meters(this last was the bigger north side)...Now some things are not clear to me...When they describe the battle, they say Turkish guns were placed on right bank of small river...I went and visited whole place, that river or at least what was left from it is from cliff of hill away some 2 to 5 km...Napoleonic cannons fired for 500 meters plus minus as I heard...