The first scale factor you give is 13mm per 100m, the second one you give 34mm per 100m.
You can only use one scale factor for an observation, the second one would be consistent with your distance errors. The scale factor can't change that much over a few hundred metres.
Yup. You are right. Wish I could edit, as wrote number wrong...damn tablet.
First point I am shooting from has a point scale of 0.99965861. The point I am shooting to has a point scale of 0.99965882. Question is, which one to put into machine...or is the difference so small it does not matter?
Point scales were derived from http://www.ga.gov.au/geodesy/datums/redfearn_grid_to_geo.jsp&apos ;">www.ga.gov.au/geodesy/datums/redfearn_grid_to_geo.jsp.
Just a shot in the dark...some prisms are reversible. It's possible you actually have it on the -30mm side.
Although that wouldn't explain the vertical error.
UTM scale factors are not close to 1 especially at high altitude (further above the grid plane).
Mate. I'm a bit closer (WA Pilbara) but still too far to come visit. Here's my take and I have had these issues before using grid versus ground.
Look at the scale factor and to dumb it down, 0.99965861 is 99.9658m = 100m, and that's 35mm right there. The second one is 99.9659m = 100m and that's 34mm. Either way, over 150m, multiply by 1.5 and viola = 52mm odd and that's the error you're reporting.
Change the instrument scale factor to one of the above - they're so close it doesn't matter in your situation - and I think you'll find every thing will be bonza, smicko, @#$%ing A1.
Did I tell you the auto censor fixes swear words for you on this site, what a @#$%ing laugh!!
use either it won't make any difference. then you need to sort out your vertical problems.
check the levels between the stations with a level. if the published values are correct using the level then you need to look at checking your target heights and sighting in both faces to try to eliminate errors.
Thanks all for the responses. I have a few things to check now, which is exactly what I was after. I will post back with results, just in case others encounter such a seeming dead end.
Paul the Irishman: Pilbara eh? Bit too hot for me! Your answer perfectly laid out the problem enough for an archaeologist to understand. It really does seem like the scale might be the issue, so I look forward to trying the revisions on Monday.
Weakwilled
weakwilled15, post: 347454, member: 10822 wrote: Hello Bill93 and kjpls. Your suggestions have raised the possibility of local scale error. I am in UTM (s) 55 and, according to a websitey-thing for Geoscience Australia I found, I should have a local scale of 0.99986851 for the point I am shooting from. The point I am shooting to has one of 0.99965882. I know the machine is set to a scale of 1. Is that difference really going to account for the displacement error?
Kjpls, I can photo the setup if it will help...
You may need to multiply the scale factor by an elevation factor to get one combined factor to multiply your ground distances by. Unless I missed it, I did not see if your measurements were short or long compared to the SPM data.
Hi all. Just to report back. After a day of annoyances (related to misbehaving data collecting software) it turns out your suggestions re the local scale were entirely correct. Calculated a combined scale factor, put it in the Nikon and voila! got my stations established with little hassle. Scale factor is probably Survey 101 for you guys, but was something I had never had to consider before. Thanks to everybody who took the time to help, I appreciate it greatly.
Weakwilled
weakwilled15, post: 347690, member: 10822 wrote: Calculated a combined scale factor, put it in the Nikon and voila! got my stations established with little hassle. Scale factor is probably Survey 101 for you guys, but was something I had never had to consider before.
Weakwilled
Here is a link to the technical manual.
http://www.icsm.gov.au/gda/gdatm/gdav2.3.pdf&apos ;">Geocentric Datum of Australia
And here is a link to a paper on Height Scale Factor (Aust.)
http://www.minesurveyors.com.au/files/2013Conference/1130-Chris-Hutch-Height-Scale-Factor-Presentation.pdf&apos ;">Height scale Factor - Presentation Paper
Barry Graham
Melbourne, Australia