I am using a Leica LS10 digital level and it is giving me values to 5 decimal places. Are they really measuring to that level of precision? I get great closures with it.
You can change the display. If I recall correctly there is some nominal bump up in precision from the DNA 03 line. The manual has the information you seek and I must say is much better written than earlier generations of Leica manual. The color screen and interface is also better than in years past but I do not know if on the whole it is worth the extra two and a half pounds of weight they put on her.?ÿ
These fluctuations of size and weight in tech are frustrating, you could put a HP48 DC in your jacket pocket, an Allegro or Ranger could fit in the vest with some working, now they got stuff like the TSC7 which almost needs a backpack to carry.
Cell phones are another example, brick to candy bar to flip phones that were too small and now they have these flat screen phones that do not fit in a pocket which is in turn making clothing manufactures make pockets too big to hold anything but a smartphone.?ÿ
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I am using a Leica LS10 digital level and it is giving me values to 5 decimal places. Are they really measuring to that level of precision? I get great closures with it.
The data sheet says 0.3 mm rms accuracy on 1 km double run using invar staff. If each sight was 100 meters, it would take 20 readings for the loop. 0.3/sqrt(20) = 0.067 mm = 0.00007 meter needed per sight. So it does need to carry at least 5 places to avoid excessive rounding error.
That's 0.14 arc second, which is pretty amazing.
Don't mix up precision and accuracy. Even on a 30m. sight you can get quite large variations in refraction. Just with the ray passing very close to the ground (or just over a vehicle roof) will throw the sightline. That's not so bad if the obstruction is mid-line as both directions might have more or less the same error (if the times were close and the temperature remained the same), but if the obstruction is at one end of the shot then the reverse could have a completely different refraction error.
You can sometimes demonstrate this to disbellievers by setting up two points and reading between them. Then place a shiny roof vehicle between them and set the level so that it JUST clears the roof and read again. Especially if it is sunny then you can show quite a difference.
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Precision depends on the instrument (it's a factor of the design). Accuracy depends on the surveyor.
Precision is the ability to get the same answer, whether it is right or wrong: accuracy is the ability to get the right answer.
My apologies for poor wording. I wasn't thinking when I copied the word accuracy from the Leica brochure.
Borrowed from the CLSA board today:
I am guessing that the precision of the instrument exceeds the expected accuracy...which is what I take the statement by Leica to be...a statement of expected accuracy. Generally, they note the conditions and tools (invar rod, etc) connected with the statement.
I mainly wondering is it really measuring to a 1/100 of a mm? If it is that is pretty incredible.
I believe this is the best you can do here
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@rj-schneider If you are trying to read read 0.015 mm then your significant digits must go out to 0.001 mm.?ÿ That does not mean you results will be anymore precise that 0.015 mmm, just that rounding errors do not exceed the precision of of the combined observations.
you're right, I was making the comparison of the digital level to it's components. As far as I know (disclaimer here) the Nedo invar leveling rods are about as good as it gets.
Remember that with this level of accuracy cleanliness is absolutely vital. You certainly won't be running km. length lines across muddy fields. More likely carrying out some percision engineering set-up, such as baseplate levelling for heavy machinery which is rotating at high speed.
Stave end and measuring point need cleaning before each reading with a suitable solvent to remove even the slightest speck of dust, if you really need that 1/100 mm.
For monitoring work I've sometimes used stainless steel rules epoxied into place with the rule end on the surface being monitored. As long as you can set up so as to read within a few cm. of the zero then expansion doesn't come into it and the advantage is that the rule is ALWAYS in exactly the same place, so you do get a true record of any changes which occur.
We run a settlement survey once a year over a salt mine. Every 5 years we bluebook it (this year for the third time). Always done in November or December. There are groupings of points that we know are settling, and others that we believe are stable. This year the observed delta elevations on several sections between stable points matched last year to the 0.1 mm. Others were a couple of tenths of a mm agreement. And these points are not right next to each other, typically hundreds to thousands of meters apart. So it is possible to get <1 mm accuracy on sections. The dini 12 level spec is 0.3 km. But of course we are leveling outside, in the wind (this is on Lake Erie), cold, etc. Using 3 m invar rods with struts and good turning plates.?ÿ
But the settlement amounts even on the "unstable" points are only mm per year, unlike a coal mine where settlement is more sudden and can be decimeters. Last year we monitored an interstate highway over a long wall mine during several months of mining, I was surprised that the horizontal movement was actually larger than the vertical movement on many points.?ÿ?ÿ
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