StarNet Preanalysis: who is using Preanalysis and how?

Dam monitoring surveys. The St. Louis District of the USACE has all of their lake dams and river lock and dams surveyed annually. Each dam has a series of monuments on them that are leveled through and shot from at least three control monuments that are offsite. These control monuments are like 1' diameter concrete that go down to bedrock with stainless steel forced centering mounts for a plate that the total station screws on to. The covered wooden towers were built around these. Some still had the old pulley to hoist the old EDM out of the truck and on to the CM. That was replaced by the Kern Mekometer 5000, which I had the privilege of using and retiring in 2008. We phased in the Trimble S-8 in 2008. This method went on for decades up until about 2019 when they decided, after some analysis, that the data was sloppy and could be better. They wanted to get the accuracy down to 3mm on the horizontal. I thought they were out of their minds when some distances from those CM's to the dam are up to 19,500' away (Rend Lake). Carlyle has a CM that's 17000' up the lake. We located all of the monuments by GPS, including the CM's which had their roof's removed or new steel towers were built. Put that in the Star*Net Preanalysis and ran until we got to the 3mm threshold that we were needing. At Carlyle Lake, we needed to shoot each dam monument 10X, from 3 different CM's. We turned the tri-brach a third and re-centered over the monument after every shot. It's an arduous task but it achieves what they are looking for. Well, that's the cliff notes of it anyway. There's a wee bit more to it.

I also use it for monitoring projects. Best program by far for estimating how many observations you're going to need for a particular tolerance - or for telling you that your gear isn't efficient enough and you need something different!

Edit to add: there's not much to scrutinize, other than seeing how error propagation affects the network & local accuracies of the final coordinates, and whether they meet specified tolerances. Since we're not looking at or comparing real-world observations, there aren't any standardized residuals or reference factors to evaluate. Of course, the user-input standard errors for the instruments and/or measurements better be darn close if you want a realistic result.

I've only used it a handful of times to get a sense of estimated errors on some unusual network configurations. It's been a way to reality-check what my gut tells me.

We use the preanalysis to assist with designing static GNSS survey networks. It's so quick to put together your planned baseline observations, and of course seeing the estimated uncertainties are a great help to quickly identify areas of weak geometry. There's a lot more to static networks than just geometry, but it's a great tool to assist wtih the design, plus after completing the preanalysis you can print your input files to help with field work logistics.