This is Page 19 from Jim Conkright's field notes. The area must've been recently clear cut because I'd be lucky to see 150 feet in some of his mile plus measurements. I don't know if this was the HP3805 he was using. The nearest page with a date (a few pages back) is in October 1977. The first page of his computations on traverse sheets is in August 1977. His computations in pencil use the calculated horizontal distance of 7899.12. At some unknown date he added in red the correction of -0.52 feet from 2000 meters (6561.67) and changed the calculated horizontal distance of 7896.60. I don't know where the -0.52 Correction comes from? At some unknown date he corrected his computations on the traverse sheets with a purple felt tip pen.
In the same file are found the following notes from June 1979. He uses a correction of -0.72. He says the published baseline distances are from the Division of Highways. No mention is made of the 2000 meters. On page 21 of the same notes above he adds 2000 meters to a measurement with no mention of a correction.
Any comments would be appreciated.
Dave Karoly, post: 405107, member: 94 wrote: This is Page 19 from Jim Conkright's field notes. The area must've been recently clear cut because I'd be lucky to see 150 feet in some of his mile plus measurements. I don't know if this was the HP3805 he was using. The nearest page with a date (a few pages back) is in October 1977. The first page of his computations on traverse sheets is in August 1977. His computations in pencil use the calculated horizontal distance of 7899.12. At some unknown date he added in red the correction of -0.52 feet from 2000 meters (6561.67) and changed the calculated horizontal distance of 7896.60. I don't know where the -0.52 Correction comes from? At some unknown date he corrected his computations on the traverse sheets with a purple felt tip pen.
Any comments would be appreciated.
HP published the procedure for the HP 3810A to obtain distances beyond a 2000 meter measurement. It is possible that this also applies to the 3805. I have the document if you would like a copy e-mailed to you. I used it several times with my 3810A's when making measurements beyond the 2000 meter reading per the instrument. I did a check the first time I did the procedure by setting a point in between and measuring both ways and if I remember correctly there was only .005 difference in measurement output.
Charles L. Dowdell, post: 405113, member: 82 wrote: HP published the procedure for the HP 3810A to obtain distances beyond a 2000 meter measurement. It is possible that this also applies to the 3805. I have the document if you would like a copy e-mailed to you. I used it several times with my 3810A's when making measurements beyond the 2000 meter reading per the instrument. I did a check the first time I did the procedure by setting a point in between and measuring both ways and if I remember correctly there was only .005 difference in measurement output.
Yes, I would appreciate that:
david dot karoly at fire dot ca dot gov
Thanks.
Whenever you are measuring beyond the 2000 meter point, remember to set the atmospheric correction (AC) to zero. It will only correct what distance is displayed that is over the 2000 meters. So it is imperative to set the AC to zero, write down the distance displayed and then add the 2000 meters to it and then run through the calculations for the correction by hand. That way you can get a real slope distance overall then reduce to horizontal. The HP 3810B had a hotter diode in it than the 3805 or the 3810A. I believe the HP Museum has some information about this also. Best of luck.
I think Caltrans calibrated the base line at the Yolo County Airport, so that may be the Division of Highways reference.
I used one of those marks (YOLO COUNTY AIRPORT BASELINE POINT 6, PID DE9129) for a height mod project back when you could just drive out to it. Now the whole airport is fenced and you have to get permission and gate codes to get to it, which limits its usefulness.
I'm wondering out loud if he was using an array of reflectors that were not HP and had a weird prism offset. The prism constant was fixed internally for use with HPs prisms. Lord knows what he was using for distances like those. I remember some really funny contraptions back in the day.
Here's a link to a 3805 op manual. It does discuss errors in distances over 2000 meters.
http://literature.cdn.keysight.com/litweb/pdf/03805-90001.pdf?id=1865208
[SARCASM]Q1 Did you find the monuments?
Q2 Who cares? [/SARCASM]
Using the 3810A manual Charles emailed to me I calculated the distance corrected for curvature & refraction:
So now I'm going to have to move all of his monuments 8 hundredths, what a pain 🙁
Oops...after I posted that I saw my mistake in cell E7 (should be 1336.40):
The calculation he had without C&R is 7896.60 so now I only have to move them 3 hundredths!
Dave Karoly, post: 405136, member: 94 wrote: Oops...after I posted that I saw my mistake in cell E7 (should be 1336.40):
The calculation he had without C&R is 7896.60 so now I only have to move them 3 hundredths!
Probably best to just use the trusty virtual inclusion table an show the delta n &e from the true positions.....
Dave Karoly, post: 405136, member: 94 wrote: Oops...after I posted that I saw my mistake in cell E7 (should be 1336.40):
The calculation he had without C&R is 7896.60 so now I only have to move them 3 hundredths!
Now you have to move your own monuments! Ha! :p
I hate it when that happens!
A big enough dimple ought to cover it ...
