[Proj] How to transform between NAD83 HARN/HPGN and WGS84

Thu Feb 19 13:25:47 PST 2009

Professor,

I didn't intend to imply that a better transformation package existed. I
was speaking about "recomputing an entire original traverse on another
datum", but I didn't make that clear.

I was recommending that one consider the purpose of the data
transformation before deciding to use ANY transformation package. If I
was building a nuclear reactor I would want to perform field surveys to
tie into local survey control.

Aaron is probably fine using CopsCon. I just get nervous when I hear
"sub-foot" accuracy. Usually when you are dealing with coordinates at
that level of accuracy you are leaving the GIS arena and entering an
arena that demands field work to reference local control on the ground.

I apologize for the confusion.

Landon

Office Phone Number: (209) 946-0268

Cell Phone Number: (209) 992-0658

________________________________

From: proj-bounces at lists.maptools.org
[mailto:proj-bounces at lists.maptools.org] On Behalf Of Clifford J Mugnier
Sent: Thursday, February 19, 2009 12:47 PM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] How to transform between NAD83 HARN/HPGN and WGS84

The analogies are incomprehensible as offered.  CorpsCon performs State
Plane and UTM transformations to better than a tenth of a millimeter
round-trip accuracy.  The datum transformations are kosher NGS NADCON in
that they use the original NGS data files.  There is no better tool
available other than re-computing an entire original traverse on another
datum using the new endpoint coordinates.

NADCON is the official method to transform among the U.S. North American
Datums as published in the Federal Register.  CorpsCon was written by
the U.S. Army Topographic Engineering Center and uses the original
NADCON data files as developed by Cdr. Warren Dewhust of the U.S.
National Geodetic Survey.  TEC used NGS 5 as the authoritative source
for the equations for the State Plane Coordinate Systems as also
declared and published in the Federal Register.

Whether transforming gopher holes or tiepoints for a nuclear reactor,
there is no better transformation package available.

C. Mugnier

LSU

________________________________

From: proj-bounces at lists.maptools.org on behalf of Landon Blake
Sent: Thu 19-Feb-09 13:22
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] How to transform between NAD83 HARN/HPGN and WGS84

I'd be careful using something like Corpscon for data that is sub-foot
accuracy and needs to stay that way.

We wouldn't use that program or any like it to convert data that needs
to be that accurate. I don't know what the purpose of Aaron's data
conversion is, but he might need to be careful.

Transforming the location of gopher holes using Corpscon is one thing.
Transforming building corner positions, or the alignment of a new
pipeline with Corpscon is another thing entirely.

Landon
Office Phone Number: (209) 946-0268
Cell Phone Number: (209) 992-0658

-----Original Message-----
From: proj-bounces at lists.maptools.org
[mailto:proj-bounces at lists.maptools.org] On Behalf Of Richard Greenwood
Sent: Thursday, February 19, 2009 10:42 AM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] How to transform between NAD83 HARN/HPGN and WGS84

Corpscon (http://crunch.tec.army.mil/software/corpscon/corpscon.html)
based on NADCON is a good, free, authoritative tool when working in
the US.

Regards,
Rich

On Thu, Feb 19, 2009 at 10:20 AM, Aaron Friesen <aaron at cartopac.com>
wrote:
> Everyone,
>
> I checked the archives for the past year and did not find an
> answer to this.  Google did not provide me with any leads
> either.
>
> I have data in NAD83 HARN for Colorado.  I need to take the
> data into the field as WGS84, update it/add to it, and get
> it back as NAD83 HARN for Colorado.  The data I am collecting
> has sub-foot accuracy, so "close" is not good enough.
>
> The information on the grid files does not address the
> HARN/HPGN question.
>
> Is this type of transformation with the accuracy I need
> possible with Proj?
>
> Are HARN grid files available or are towgs84 settings defined
> for the various HARN areas?
>
> Or am I stuck looking for an alternative, commercial solution?
>
> Thank for your assistance.
>
> Aaron
>
> _______________________________________________
> Proj mailing list
> Proj at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/proj
>

--
Richard Greenwood
richard.greenwood at gmail.com
www.greenwoodmap.com
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