1025 will be the 'ground to ground' measure of a full awning, and this is what is quoted by manufacturers of awnings, you will usually find a range quoted (e.g. 1025-1050). If you imagine a piece of string running around the rail and to the ground in a diagonal fashion at each end, then this will be the 1050.You quote a Vakela porch, so the 280 would be the width along the caravan wall when erected, and there will also be a projection measurement, perhaps 250, 300, or 350. So if you take a tape measure to the side of the van will the 280 fit including the door without the edges obstructing windows or hatches. There are a wide variety, many 'air awnings' with pumped tubes, although often any poles that fit (usually in sleeve or Velcro fastenings) upright within the awning material adjacent the caravan wall may be aluminium or steel. I have never used any, but ensure that the rear of the awning is then taut and not flapping about in the wind. My last note would be to consider the floor area that you need, we just have 2 chairs and a small 'coffee' table in ours, but make sure that the area gives room for your needs.