Hi Guys
I finally got myself a proper theodolite and 2" horizontal angle sets
were fairly easy to achieve straight out of the box.
The only thing I can't get right are zenith angle measurements,
it looks to me like the index is not adjusted properly.
Take picture 2 for example I'm not sure if I should read
it as 274-56-31 or 275-06-31.
If you have seen this before and could give me a hint
what to adjust it might save me a trip to the local
Leica guys who most likely charge more for the adjustment
then the theodolite cost.
Looks like 273-40 + 6-31 = 273-46-31
Picture 1 = 273°-47'-38"
Picture 2 = 275°-06'-31"
I haven't used that model, but my textbook seems to indicate the values are always added, so the 2nd one would be 275°-06'-31". If it was 274°-56'-31" you would be centered on the mark 2/3 of the way between 274 and 275 (274° 40') and reading 16' 31" on the bottom.
If you are having trouble getting good vertical measurements, perhaps it would help diagnosis if you set up and carefully leveled the instrument, and then took repeated direct and reverse measurements on the same point. Do the values repeat or is something loose? Do the D+R add up to near 360 degrees or is the index far off?
Repeat for some points at other vertical angles so you are reading at different parts of the micrometer scale.
Also, it looks like your coincidence of marks in the top picture could be improved.
I see what I did
I thought the two pics were of the same reading - just that the upper pic was for the degree & 10's of minutes reading and the bottom pic was for the micrometer. That's what I did. But I agree that 273-47-38 would be correct for the top one.
I think all T2s with that version of the reading micrometer had manual bubbles, not automatic ones, so don't forget to level up the vertical circle bubble before you set the reading scale - it should be the knob which isn't knurled, but has 122 grips around the circumference.
I agree with the readings above.
Looking at the top image the degree reading is 273. Count the number of division lines from the 273 to the inverted number 93. We match the same end numbers in the lower and upper part of the top scale. Each division is ten minutes. We add the seven in the bottom scale to the minutes and read the seconds directly.
In the bottom image there are no divisions between 275 and 95 therefore there are no tens of minutes. The reading is 275d 06m 31s.
> I haven't used that model, but my textbook seems to indicate the values are always added, so the 2nd one would be 275°-06'-31". If it was 274°-56'-31" you would be centered on the mark 2/3 of the way between 274 and 275 (274° 40') and reading 16' 31" on the bottom.
>
> If you are having trouble getting good vertical measurements, perhaps it would help diagnosis if you set up and carefully leveled the instrument, and then took repeated direct and reverse measurements on the same point. Do the values repeat or is something loose? Do the D+R add up to near 360 degrees or is the index far off?
>
> Repeat for some points at other vertical angles so you are reading at different parts of the micrometer scale.
>
> Also, it looks like your coincidence of marks in the top picture could be improved.
Thanks for the suggestions Bill, I've got another week in the West Australian bush
but as soon as my R&R starts I'll shoot some zenith angle sets, last time I gave up
because I just couldn't work out how to read the circle.
> I think all T2s with that version of the reading micrometer had manual bubbles, not automatic ones, so don't forget to level up the vertical circle bubble before you set the reading scale - it should be the knob which isn't knurled, but has 122 grips around the circumference.
Didn't have a manual when I first tried but noticed the coincidence level mirror
and had it properly leveled.
Your best check is read them direct and reverse to the same point and see if the answers add up to 360. That will tell you that your circle is good or bad and/or you are reading something wrong.
