Just out of curiosity, what do you mean by "not very accurate"? The Geo X* series minus a fixed antenna can be wielded around like a garden hose for hand held work. That said the experienced user can do some fairly decent "rough" checking of heights by being somewhat disciplined with the units. I used a rough HI measured to my shirt pocket and held the unit very still during observations. Using Terra Sync to collect and Pathfinder Office to process I was stunned by the "accuracy" I would sometimes experience, actually as close as sub foot over known points at times. But there were also results that were a little less accurate, so to speak. Using a fixed height external antenna with the XH gives much improved repeatability in your orthometric heights. But even then, those elevations are only useful as a check.