Community Forums

Odd thing happened,...
 
Share:

Odd thing happened, points staked about 4.5' off  

Page 1 / 4

Mark O
Posts: 128
Member
(@mark-o)
100+ posts
Joined: 3 years ago

First time occurence and it scared the .... out of me. I staked about half dozen points using RTK and only learned today (a month later) they were all off by about 4.5' to the north-northwest. Fortunately this wasn't a costly mistake. I went back out with both RTK receivers I have and same points staked in correct locations.  I'm guessing maybe a default setting may have changed? Maybe "Convert WGS84 to NAD83" was checked, or somehow it loaded an older geoid model?

I initially thought maybe it could be a US/International Survey foot issue, but that doesn't seem to be the case.

If anyone has ever had this experience and knows what may have happened, I'm all ears.  

24 Replies
linebender
Posts: 730
Member
(@linebender)
500+ posts
Joined: 9 years ago

It's not the geoid. I'm betting on wrong datum designation. And yes we have seen it before. In our software it's the difference between (NAD83 No_Trans) and NAD83. It may be called something else in your software.

Always check into a known point before, after and during RTK sessions.

 

Reply
John Hamilton
Posts: 2498
Member
(@john-hamilton)
1,000+ posts
Joined: 9 years ago

Sounds like ITRF versus NAD83(2011). Trimble had a poorly named transformation that confused people, but sometime ago they changed the name to be more clear. You don't say what DC you are using. 

Reply
StLSurveyor
Posts: 1462
Member
(@stlsurveyor)
1,000+ posts
Joined: 6 years ago

Do you use C3D to calc your points? Check to make sure your base file and xrefs are all set to US Survey feet - and don't forget to look for units. In 2018 you have feet and US Survey feet...If units are not set to US Survey feet your referenced blocks will be off about 4.5 feet.

Reply
Lee D
Posts: 2243
Member
(@lee-d)
1,000+ posts
Joined: 6 years ago

4.5' sounds more like feet / international feet to me; ITRF - NAD83 isn't usually that much in the horizontal (assuming the error was Hz). We see this from time to time with Civil 3D, you have to be very careful that everything is in US feet.

Reply
Page 1 / 4