There are a number of "photographic" tripods with legs made this way including film and video tripods made by Sachtler and many others. These three or four section tripod leg design tends to be more stable, more difficult to jam-get stuck and overall far more rugged and tough in difficult terrain than the single telescopic leg design. Lock down at the set length is often extremely positive with absolutely zero slippage. Some of the surveyor's tripod legs have a solid center section that extends with two outer sections making them seriously stable, tough and really strong.
IMO, aluminum is not a good tripod leg material choice. Materials such as wood, fiberglass and carbon based composites (too expensive IMO) are superior to aluminum. Search on flea-bay and other auction sites will reveal non-photographic tripod legs of very high quality can be had for well under $200, typically in the $100 range. IMO, brands like Gitzo, Manfrotto-Bogen, and others are over priced for what they offer.
Bernice
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