Edit: it looks like you just copy/pasted the subtitle from Smithsonian. Do you have any additional commentary that might enlighten the rest of us who are trying to decide whether to read the article?
No literal groundbreaking involved, just somewhat remote sensing, at least this time. (The Ground-penetrating radar (GPR) will reflect off jumps in eletric permittivity in the ground, which are caused by changes in material, and especially by different water contents, which can also be an indicator for different materials (such as stone in soil, or sand in soil, or soil in different soil - material with smaller pores can retain more water due to capillary effects).)
ground-breaking - related to the actual act of breaking ground
Not sure how you don't know this, unless opening a dictionary would be a groundbreaking experience for you.
I spent two years in an occupation where the most entertaining thing to do was to read the dictionary for fun. The fact that someone, somewhere, defined a difference between the hyphenated and compound forms of the term doesn't mean that everyone is using those forms as defined; thus my request for disambiguation remains relevant.
Edit: also:
$ dict groundbreaking
2 definitions found
From The Collaborative International Dictionary of English v.0.48 [gcide]:
groundbreaking \ground"break`ing\ n.
The ceremonial breaking of the ground to formally begin a
construction project. It is sometimes carried out by an
official who digs the first spadeful of dirt from the ground,
to begin the preparatory excavation work.
Syn: groundbreaking ceremony.
[WordNet 1.5] groundcover
From WordNet (r) 3.0 (2006) [wn]:
groundbreaking
adj 1: being or producing something like nothing done or
experienced or created before; "stylistically innovative
works"; "innovative members of the artistic community";
"a mind so innovational, so original" [syn: {innovative},
{innovational}, {groundbreaking}]
n 1: the ceremonial breaking of the ground to formally begin a
construction project [syn: {groundbreaking},
{groundbreaking ceremony}]The OED doesn't comment on the act (ritual) of breaking ground, but Wikipedia does, and it uses the un-hyphenated form. https://en.wikipedia.org/wiki/Groundbreaking . (Wikipedia is not, of course, the most reliable possible source, but it does indicate that the un-hyphenated form is in wide use for the literal act).
My strong suspicion is that the colloquialism arose as a metaphorical back-formation of a participle from the gerund + object compound used for, you know, ritually inaugurating (inaugerating?) a building project.
Edit: removed ill-considered emoticon.
A mere upvote is insufficient for this groundbreakingly clever pun. For reference:
auger
2. An instrument for boring or perforating soils or rocks,
for determining the quality of soils, or the nature of the
rocks or strata upon which they lie, and for obtaining
water.groundbreaking
[ground-brey-king]
noun
1. the act or ceremony of breaking ground for a new construction project.
ground-breaking
adjective
1. innovative a ground-breaking novel