Debate: Is ground-penetrating radar better than old-school test pits for finding buried structures?

I've been volunteering on digs for about 5 years now, and I keep going back and forth on this. Last summer on a site in upstate New York, we used GPR to map out what we thought was a 19th century cellar hole. The radar showed these clear rectangular anomalies, so we skipped the test pits and went straight for a trench. Turns out it was just a patch of dense clay, total waste of a weekend. But then two years ago on a different project in Vermont, the GPR nailed an old foundation that test pits would have taken us a month to find. So which is actually better for initial site assessment? I feel like GPR gives you this false confidence with its pretty pictures, but test pits are slow and you miss stuff between them. Anyone else deal with this and have a strong opinion on which approach saves more time in the long run?

3 comments

3 Comments

the_henry2mo ago

Total waste of a weekend" - yeah, I've been there, and it's why I lean toward test pits for first looks. GPR is great when it works, but when it doesn't you just wasted time you could've spent actually digging.

oscarb712mo ago

Funny you say that because I actually see it the other way. GPR has saved me more weekends than test pits ever have. Spent years digging random holes hoping to find something only to hit rock or a pipe or nothing at all. At least with ground radar I get a look first before I break my back with a shovel. Test pits are fine for small areas but they wreck your site and take forever. GPR gives me a real plan before I commit.

noah8801mo ago

See, I gotta push back a little on that one, @oscarb71. Test pits don't have to wreck a site if you're careful about backfilling. I've done plenty where you can't even tell I was there after. And yeah GPR can give you a plan, but it's only as good as the soil conditions and the guy running it. The thing nobody talks about is how GPR guys sometimes oversell what they can see... then you're standing there with a shovel staring at a spot they flagged and it's just a rock. So I get the time saved argument, but I've had it go both ways too many times to fully trust it.