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138' Discrepancy in Horizontal Datum. How?

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paul-in-pa
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I'll go along with Dan Dunn, I surmise he scaled it from the 0,0 reference point rather than the local coordinate he was using as base.

Paul in PA


 
Posted : June 2, 2017 9:48 am
john-hamilton
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Larry Scott, post: 430765, member: 8766 wrote: Don't forget car batteries and walkie-talkies, the big Motorola kind. Key the mic and slip on all 5 channels.

We actually had one receiver (very early Trimble 4000 model) that was 24V only. So you needed TWO car batteries. And yes, I remember the cycle slips from nearby radio transmissions. When I surveyed on USVI in the early 90's there were no first order points on the island, just a single second order point on a high hill on St Thomas. It was at the base of a microwave tower, and we could not get any GPS signals there. I had to set an eccentric just over the crest of the hill to be able to tie it in. The came the SSI...

Had one situation where this cop pulled over down the road and pointed his radar my way. Wiped out all of the signals, and i went and told him about and of course he told me to get lost.


 
Posted : June 2, 2017 9:58 am
muncle56
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Thanks everyone for your input. Multiplying by the scale factor does get me closer to SPC but there's still no consistency. I'm going to use the existing control to do a localization and leave the project on it's original datum (whatever that is).


 
Posted : June 6, 2017 5:30 am
MightyMoe
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muncle56, post: 431233, member: 8893 wrote: Thanks everyone for your input. Multiplying by the scale factor does get me closer to SPC but there's still no consistency. I'm going to use the existing control to do a localization and leave the project on it's original datum (whatever that is).

what happens if you accept the data and survey using it?


 
Posted : June 6, 2017 6:01 am
thebionicman
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muncle56, post: 431233, member: 8893 wrote: Thanks everyone for your input. Multiplying by the scale factor does get me closer to SPC but there's still no consistency. I'm going to use the existing control to do a localization and leave the project on it's original datum (whatever that is).

Just remember, localizing means screwing things up the same way the other guy did (which is a lot of what we do measurement wise).
The key is to determine if everyone can live with the results. I prefer to compute the distortions ahead of time, but there is value in evaluating it on site for certain jobs. Look at rhe parameters generated by your localization. If they are reasonable run with it. Good luck, Tom


 
Posted : June 6, 2017 9:18 am

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