Author Topic: Survey Question - Project to WGS 84  (Read 8166 times)

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nobody

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Survey Question - Project to WGS 84
« on: May 17, 2016, 09:48:39 PM »
What's it take to get from project coordinates (on no known coordinate system) to WGS 84 with a decent level of accuracy?

BlackBox

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Re: Survey Question - Project to WGS 84
« Reply #1 on: May 18, 2016, 03:16:51 PM »
What's it take to get from project coordinates (on no known coordinate system) to WGS 84 with a decent level of accuracy?

That depends on your definition of 'decent'. Haha

We usually correlate a project about 2-3+ known points (i.e. bench marks, found monuments, etc.) that have an online formal record to validate.
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nobody

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Re: Survey Question - Project to WGS 84
« Reply #2 on: May 18, 2016, 05:59:40 PM »
Back in the day I'd use the Trimble survey equipment and software to do this with the points... but I never did figure out how to make the adjustments for linework in CAD.  Right now I'd try to find 2/3 points, like you say below...then adjust them coordinate-wise with a best fit. Then I'd use the mapexport to send it to wgs 84...then start a new drawing in wgs 84 and import the linework back in.  Seems flim-flammery though.  I don't feel that's properly accounting for the ellipsoid junk I always hear peeps talking about.

What's it take to get from project coordinates (on no known coordinate system) to WGS 84 with a decent level of accuracy?

That depends on your definition of 'decent'. Haha

We usually correlate a project about 2-3+ known points (i.e. bench marks, found monuments, etc.) that have an online formal record to validate.

mjfarrell

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Re: Survey Question - Project to WGS 84
« Reply #3 on: May 20, 2016, 10:30:53 AM »
What's it take to get from project coordinates (on no known coordinate system) to WGS 84 with a decent level of accuracy?

Stop using fictitious coordinate systems....

what we do here is sort of a modified state plane, grid @ ground, sort of the best of both worlds...
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nobody

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Re: Survey Question - Project to WGS 84
« Reply #4 on: May 26, 2016, 03:41:23 AM »
Easier said than done. A lot of the projects I work on are master-planned communities with 20-year old established coordinate systems. 

Before I moved to this state we did a similar thing...it was truncated version of the state plane simply because the coordinates were much too large.  Made it easy to use GIS data.

Still though...don't feel there's enough information about these conversions (from state plane to wgs 84, etc) in regards to the software...specifically relating to procedure, concerns, accuracy, etc.

What's it take to get from project coordinates (on no known coordinate system) to WGS 84 with a decent level of accuracy?

Stop using fictitious coordinate systems....

what we do here is sort of a modified state plane, grid @ ground, sort of the best of both worlds...

mjfarrell

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Re: Survey Question - Project to WGS 84
« Reply #5 on: May 26, 2016, 08:44:42 AM »
IF the data is collected on any known coordinate system then translating to any other known
coordinate system is as accurate and easy.

However trying to go from any fictional coordinate system to a know will or may introduce errors without enough
common points for reference.  Although a point transformation can be down with some survey software
like Trimble Business Center.  Although your results are dependant on number of points use to compute the transformation.


We use state plan, and there is no issue with "large coordinates",  and we use GIS data. Which most likely is on
State Plane and or WGS84, or otherwise still large coordinates.
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Michael Farrell
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cadtag

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Re: Survey Question - Project to WGS 84
« Reply #6 on: May 26, 2016, 09:53:17 AM »
well, the large SP coordinates (in the millions around here) do tend to result in rounding errors in Acad.  Not a biggie, just a pita.
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snownut2

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Re: Survey Question - Project to WGS 84
« Reply #7 on: June 11, 2016, 01:32:27 PM »
Have you looked at this.....

http://vdatum.noaa.gov/


mjfarrell

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Re: Survey Question - Project to WGS 84
« Reply #8 on: June 13, 2016, 08:35:41 AM »
Have you looked at this.....

http://vdatum.noaa.gov/

Interesting, however not sure it helps when no datum, no projection is the origin of the data...as is the case specified.
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Michael Farrell
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snownut2

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Re: Survey Question - Project to WGS 84
« Reply #9 on: June 15, 2016, 11:52:55 AM »
If he can determine the Longitude and Latitude of a single point, and a bearing to another point from that point, or if he can locate a point with a known Lat&Long. he can then transform the entire point set to any coordinate system with ease.  That's how it relates to the thread, just because he is not currently tied to any coordinate system doesn't mean he is SOL.

Trimble has the surveying profession as a whole fooled into thinking you need to spend big money on thier products to achieve any degree of accuracy, the NOAA program is free, and was developed in large part by BAE systems for military applications, so I am sure the accuracy rivals Trimble's big cost products.
« Last Edit: June 15, 2016, 12:01:01 PM by snownut2 »

mjfarrell

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Re: Survey Question - Project to WGS 84
« Reply #10 on: June 15, 2016, 12:10:30 PM »
ALL the above is true, however, coordinate/datum translations can be done in several applications other than the one you mention.



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Michael Farrell
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snownut2

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Re: Survey Question - Project to WGS 84
« Reply #11 on: June 15, 2016, 12:26:24 PM »
I only addressed the NOAA site as an example of what is available as a completely free to use with no strings attached option.

cadtag

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Re: Survey Question - Project to WGS 84
« Reply #12 on: June 15, 2016, 08:39:48 PM »
Aslo the UASCOE Corpscon and Verticon programs.  Not 'free' software, but public domain  and supported by your tax dollars.,
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nobody

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Re: Survey Question - Project to WGS 84
« Reply #13 on: June 15, 2016, 10:37:56 PM »
If he can determine the Longitude and Latitude of a single point, and a bearing to another point from that point, or if he can locate a point with a known Lat&Long. he can then transform the entire point set to any coordinate system with ease.  That's how it relates to the thread, just because he is not currently tied to any coordinate system doesn't mean he is SOL.

Trimble has the surveying profession as a whole fooled into thinking you need to spend big money on their products to achieve any degree of accuracy, the NOAA program is free, and was developed in large part by BAE systems for military applications, so I am sure the accuracy rivals Trimble's big cost products.

This is essentially what I was wondering.  A single established benchmark and a bearing is this truly all that's required to convert between coordinates systems accurately?  If this is accurate, than what you say is definitely true...it's easy.  If there is any stretching involved between any coordinate systems through, wouldn't more than one point be needed for an accurate conversion...and if so, how accurate would that even be...

Probably not a big deal.  What I do now is find a few established benchmarks, match up my site with a few survey points accordingly, and just export to WGS84. At that point I just tell people who use the data it's "close but don't build off it" lol

cadtag

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Re: Survey Question - Project to WGS 84
« Reply #14 on: June 16, 2016, 08:39:25 AM »
How many feet are there in a minute of angle?  Obviously, that will depend on the distance from the center to the points being measured, so at sea level there's one distance between two lat long values, and on the Leng plateau  the distance bewtwee the same lat longs would be greater. 

And how precisly is the lat long being measured?
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