The search facilities at CorpusEye, Miland, are very powerful and perhaps should be better known to the Esperantists. However the helpnotes are tough going.

I posted a simple guide to searching with Corpus Eye in the JEB Forums, under the heading Ĉu ĝuste - mi volas kontroli. You can find it in the Learning Materials section of the JEB forums.

sunanglo:The search facilities at CorpusEye..should be better known to the Esperantists.

To this end, you may wish to set up a thread on both English-speaking and Esperanto-speaking forums of the lernu! website about it.

Miland:

ceigered:Would there be any such metric measurements in the tekstaro? I ..found nada.

This indicates, does it not, that it is not a customary usage?

Well, I found one example in La Ondo de Esperanto:

1 trovo en La Ondo de Esperanto
tas grandaj (po ĉ. 10 mil enloĝantoj), la plurkilometre longaj strandoj sufiĉas por akcepti amason da

(EDIT: Ironically in the same text it has "dekmetrojn longan" -_-')

As for customary usage, I don't know if that's the case or not since I'm having trouble using half these text searching tools, but I still think it's perfectly understandable from the get go. Heck, I'd find "du metroj longa" understandable even though it screams "I'm missing something!", only "metre longa" looks correct

Miland:

ceigered:Technically, a measurement is qualitative

"Qualitative" is not "quantitative".

Length can still be a quality though. E.g. the two metres measurement describes the state of the length. Plus, we're avoiding that messy situation where there are too many things using the accusative in the same sentence but none are technically accusative. Not that I'm saying the accusative method is bad or broken, I like the use of that "oblique" case, but I don't think it necessarily tromps the use of the adverbial ending.

Miland:

ceigered:UPDATE: duonmetre alte is in Robinsono Kruso ..Apud la postflanko de la domo staris alto ŝtonaĵo, en kiun mi faris kavernon, kaj metis la teron elfositan, ĉirkaŭ mian domon, alte duonmetre.

In my view that's bad Esperanto in a number of ways. "Alto ŝtonaĵo", too long a sentence, and last but not least "alte dunmetre"!. I would put it Malantaŭ la domo estis ŝtona monteto, el kiu mi fosis kavernon. Per la elfosita tero mi faris tavolon ĉirkaŭ mia domo. La tavolo estis duonmetron dika.

I think "alto ŝtonaĵo" is a typo (well, the alta part at least, god knows what the ŝtonaĵo is). I don't see the problem with alte duometre though. And the sentence length is just bad style no matter what language I can't say I like the translation myself either.

Anyway, to me it seems just like "Mi parolas Esperanton" vs. "Mi parolas Esperante" (inverted in this case ), except beginners will quite commonly say "Mi parolas Esperanton", but I doubt many will ever honestly try and tackle measurements quite so early on, since that sort of numerical work is always hard in another language.

Tl;dr, I agree on many accounts spare that issue with what counts as qualitative, but I find it hard to see that "-metre longa" would lose out to "-metro(j)n longa" in comprehensibility.

ceigered:to me it seems just like "Mi parolas Esperanton" vs. "Mi parolas Esperante".

The endings are respectively -n and -e, I grant you. The difference is that here the first can refer to the capability to speak a language, while the second is describing what is actually happening, and so is not a ststement about capability.
That is not like comparing La monto estas mil metrojn alta, which is an objective measurement, with .. ah, I cannot bring myself to write such perversion .

Miland:

ceigered:to me it seems just like "Mi parolas Esperanton" vs. "Mi parolas Esperante".

The endings are respectively -n and -e, I grant you. The difference is that here the first can refer to the capability to speak a language, while the second is describing what is actually happening, and so is not a ststement about capability.
That is not like comparing La monto estas mil metrojn alta, which is an objective measurement, with .. ah, I cannot bring myself to write such perversion .

Perversion? Why is it perverted when it's part of the language, using adverbs to describe adjectives isn't too bad.

Sure it may not be as stylish as the accusative, but it's all better than "mil metroj longa" .

ceigered:I still think it's perfectly understandable from the get go. Heck, I'd find "du metroj longa" understandable even though it screams "I'm missing something!", only "metre longa" looks correct

There's nothing grammatically wrong with "metre longa" and I agree it's understandable, but there is more to speaking Esperanto (and indeed any language) than simply being understood. I agree with Miland's distinction between quantitative and qualitative usage; adverbs are usually used in a qualitative way, which in this case means ideas like "sufiĉe", "nekredeble", "multe" etc. That doesn't mean you can't use an adverb for a quantity, it just means it's not usual. And if something is not usual, then IMO there's a good reason to avoid it, if possible.

ceigered:using adverbs to describe adjectives isn't too bad

Quite right. But that's a grammatical matter, and I think we're already all agreed that there's nothing grammatically wrong with it. Being grammatically correct is not the be all and end all.

Mutusen:“Duonmetre longa” doesn’t shock me, I think it’s correct and I would use it.

By the way, it means “half a meter long”.

Kompreneble! Dunno what I was thinking!