shrug-l: Surveyors, AARRGGHH!!!
stuart.korte at dot.state.fl.us
stuart.korte at dot.state.fl.us
Mon Jul 23 07:52:43 EDT 2007
It has been common practice in the past for surveyors to use assumed
coordinates especially if they were not required to tie it back to
anything. 10,000, 10,000 was used a lot for FDOT projects. There is a good
chance this might be the issue. Without the field book or metadata it is
hard to say.
Stuart Korte
Mapping Analyst
FDOT Surveying & Mapping Office
(850) 245-1581 phone
(850) 245-1556 fax
stuart.korte at dot.state.fl.us
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SHRUG-L Digest, Vol 21, Issue 11
07/20/2007 12:00
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Today's Topics:
1. Surveyors, AARRGGHH!!! (Sykes, John)
2. RE: Surveyors, AARRGGHH!!! (Tim Spivey)
3. RE: Surveyors, AARRGGHH!!! (Tripp Corbin)
4. RE: Surveyors, AARRGGHH!!! (Tim Spivey)
5. Seats still available for ArcGIS classes in Aug (Tripp Corbin)
6. Re: Surveyors, AARRGGHH!!! (Eric_Songer at URSCorp.com)
----- Message from "Sykes, John" <John.Sykes at dep.state.fl.us> on Thu, 19
Jul 2007 14:25:56 -0400 -----
To: <shrug-L at lists.dep.state.fl.us>
Subject: shrug-l: Surveyors, AARRGGHH!!!
I just received an AutoCAD file of a survey produced in the late 1980's.
Additional field work was done in 2004 and this revised survey is the CAD
file I have.
I assumed the survey work was done in State Plane Coordinates NAD83, but
when I created a projection file for this survey it ended up about 30 miles
west of the site when I let the file project on the fly!
So I went back and created a new projection file, this time establishing
the coordinates as State Plane Coordinates (SPC) NAD27. When I imported
the CAD drawing I immediately saw that the CAD drawing was coming out
southwest of where it should be by about 50 ft. I realized that the
surveyor apparently had taken a SPC NAD27 file and offset it by the
correction factor from NAD27 to NAD83 without taking into account the
difference in the offset that also exists between the two projections (I
have been told that this 30 mile offset was added to the SPCs to make if
obvious when the wrong projection was being used).
The problem is that, if I reproject the SPC NAD27 file to SPC NAD83, it
adds the offset between the two datums back in again!!! Short of getting
the surveyor to correct their file (not likely since the job was finished
in 2004) how do I get this error corrected???
By the way, I tried telling the PRJ file that the coordinates were SPC
NAD27 and the datum was NAD83, but that didn't work. Also, I found that
the reprojection tool in the toolbox doesn't work for CAD files.
Of course, ultimately I'm trying to get this whole thing into FDEP Albers
for my map.
-- John
----- Message from Tim Spivey <tspivey at tiftcounty.org> on Thu, 19 Jul 2007
14:39:36 -0400 -----
To: <shrug-l at lists.dep.state.fl.us>
Subject: RE: shrug-l: Surveyors, AARRGGHH!!!
John -
If you have an ArcEditor license, I would do a Spatial Adjustment if you
know where the CAD file should fall on the ground and have good reference
points.
I don't even bother with projections for the CAD surveys we get, just the
Spatial Adjustment tools.
The tools may be available at the ArcMap level, I'm not sure.
Tim
From: shrug-l-bounces at lists.dep.state.fl.us
[mailto:shrug-l-bounces at lists.dep.state.fl.us] On Behalf Of Sykes, John
Sent: Thursday, July 19, 2007 2:26 PM
To: shrug-L at lists.dep.state.fl.us
Subject: shrug-l: Surveyors, AARRGGHH!!!
I just received an AutoCAD file of a survey produced in the late 1980's.
Additional field work was done in 2004 and this revised survey is the CAD
file I have.
I assumed the survey work was done in State Plane Coordinates NAD83, but
when I created a projection file for this survey it ended up about 30 miles
west of the site when I let the file project on the fly!
So I went back and created a new projection file, this time establishing
the coordinates as State Plane Coordinates (SPC) NAD27. When I imported
the CAD drawing I immediately saw that the CAD drawing was coming out
southwest of where it should be by about 50 ft. I realized that the
surveyor apparently had taken a SPC NAD27 file and offset it by the
correction factor from NAD27 to NAD83 without taking into account the
difference in the offset that also exists between the two projections (I
have been told that this 30 mile offset was added to the SPCs to make if
obvious when the wrong projection was being used).
The problem is that, if I reproject the SPC NAD27 file to SPC NAD83, it
adds the offset between the two datums back in again!!! Short of getting
the surveyor to correct their file (not likely since the job was finished
in 2004) how do I get this error corrected???
By the way, I tried telling the PRJ file that the coordinates were SPC
NAD27 and the datum was NAD83, but that didn't work. Also, I found that
the reprojection tool in the toolbox doesn't work for CAD files.
Of course, ultimately I'm trying to get this whole thing into FDEP Albers
for my map.
-- John
----- Message from Tripp Corbin <tcorbin at keckwood.com> on Thu, 19 Jul 2007
15:40:52 -0400 -----
To: Tim Spivey <tspivey at tiftcounty.org>,
<shrug-l at lists.dep.state.fl.us>
Subject: RE: shrug-l: Surveyors, AARRGGHH!!!
John,
I agree with Tim. The quickest and easiest solution is to spatially adjust
the CAD file. IF you are running 9.2 then you must use the Georeferencing
toolbar. If you are using 9.1 or earlier then you use the Spatial Adjust
toolbar..
Tripp Corbin, MCP, CFM, GISP
Associate Vice President, GIS/Mapping
ESRI Authorized Instructor
Keck & Wood, Inc.
www.keckwood.com
(678) 417-4013
(678) 417-8785 fax
Keck & Wood, Inc offers instructor led and virtual training for ESRI's
ArcGIS & ArcView software.
Please visit www.keckwood.com for more information including a schedule of
upcoming classes.
From: shrug-l-bounces at lists.dep.state.fl.us on behalf of Tim Spivey
Sent: Thu 7/19/2007 2:39 PM
To: shrug-l at lists.dep.state.fl.us
Subject: RE: shrug-l: Surveyors, AARRGGHH!!!
John -
If you have an ArcEditor license, I would do a Spatial Adjustment if you
know where the CAD file should fall on the ground and have good reference
points.
I don't even bother with projections for the CAD surveys we get, just the
Spatial Adjustment tools.
The tools may be available at the ArcMap level, I'm not sure.
Tim
From: shrug-l-bounces at lists.dep.state.fl.us
[mailto:shrug-l-bounces at lists.dep.state.fl.us] On Behalf Of Sykes, John
Sent: Thursday, July 19, 2007 2:26 PM
To: shrug-L at lists.dep.state.fl.us
Subject: shrug-l: Surveyors, AARRGGHH!!!
I just received an AutoCAD file of a survey produced in the late 1980's.
Additional field work was done in 2004 and this revised survey is the CAD
file I have.
I assumed the survey work was done in State Plane Coordinates NAD83, but
when I created a projection file for this survey it ended up about 30 miles
west of the site when I let the file project on the fly!
So I went back and created a new projection file, this time establishing
the coordinates as State Plane Coordinates (SPC) NAD27. When I imported
the CAD drawing I immediately saw that the CAD drawing was coming out
southwest of where it should be by about 50 ft. I realized that the
surveyor apparently had taken a SPC NAD27 file and offset it by the
correction factor from NAD27 to NAD83 without taking into account the
difference in the offset that also exists between the two projections (I
have been told that this 30 mile offset was added to the SPCs to make if
obvious when the wrong projection was being used).
The problem is that, if I reproject the SPC NAD27 file to SPC NAD83, it
adds the offset between the two datums back in again!!! Short of getting
the surveyor to correct their file (not likely since the job was finished
in 2004) how do I get this error corrected???
By the way, I tried telling the PRJ file that the coordinates were SPC
NAD27 and the datum was NAD83, but that didn't work. Also, I found that
the reprojection tool in the toolbox doesn't work for CAD files.
Of course, ultimately I'm trying to get this whole thing into FDEP Albers
for my map.
-- John
----- Message from Tim Spivey <tspivey at tiftcounty.org> on Thu, 19 Jul 2007
16:08:19 -0400 -----
To: <shrug-l at lists.dep.state.fl.us>
Subject: RE: shrug-l: Surveyors, AARRGGHH!!!
John -
It could be worse, I suppose - you could be lumbered with landlot
lines/corners as we are in south Georgia. Three surveyors find 3 different
locations for the "same" LLC .... I actually miss the old TRS days with
water management.
Tim
From: Sykes, John [mailto:John.Sykes at dep.state.fl.us]
Sent: Thursday, July 19, 2007 2:41 PM
To: Tim Spivey
Subject: RE: shrug-l: Surveyors, AARRGGHH!!!
I have ArcInfo, so that's not a problem. The problem is I don't have very
good ground-truthing to rely on. But I might be able to use parcel corners
or TRS corners (Ha! Like they don't have problems!!!). I just called the
surveyor to try to find out what happened, so he's looking into it too.
-- John
From: shrug-l-bounces at lists.dep.state.fl.us
[mailto:shrug-l-bounces at lists.dep.state.fl.us] On Behalf Of Tim Spivey
Sent: Thursday, July 19, 2007 2:40 PM
To: shrug-l at lists.dep.state.fl.us
Subject: RE: shrug-l: Surveyors, AARRGGHH!!!
John -
If you have an ArcEditor license, I would do a Spatial Adjustment if you
know where the CAD file should fall on the ground and have good reference
points.
I don't even bother with projections for the CAD surveys we get, just the
Spatial Adjustment tools.
The tools may be available at the ArcMap level, I'm not sure.
Tim
From: shrug-l-bounces at lists.dep.state.fl.us
[mailto:shrug-l-bounces at lists.dep.state.fl.us] On Behalf Of Sykes, John
Sent: Thursday, July 19, 2007 2:26 PM
To: shrug-L at lists.dep.state.fl.us
Subject: shrug-l: Surveyors, AARRGGHH!!!
I just received an AutoCAD file of a survey produced in the late 1980's.
Additional field work was done in 2004 and this revised survey is the CAD
file I have.
I assumed the survey work was done in State Plane Coordinates NAD83, but
when I created a projection file for this survey it ended up about 30 miles
west of the site when I let the file project on the fly!
So I went back and created a new projection file, this time establishing
the coordinates as State Plane Coordinates (SPC) NAD27. When I imported
the CAD drawing I immediately saw that the CAD drawing was coming out
southwest of where it should be by about 50 ft. I realized that the
surveyor apparently had taken a SPC NAD27 file and offset it by the
correction factor from NAD27 to NAD83 without taking into account the
difference in the offset that also exists between the two projections (I
have been told that this 30 mile offset was added to the SPCs to make if
obvious when the wrong projection was being used).
The problem is that, if I reproject the SPC NAD27 file to SPC NAD83, it
adds the offset between the two datums back in again!!! Short of getting
the surveyor to correct their file (not likely since the job was finished
in 2004) how do I get this error corrected???
By the way, I tried telling the PRJ file that the coordinates were SPC
NAD27 and the datum was NAD83, but that didn't work. Also, I found that
the reprojection tool in the toolbox doesn't work for CAD files.
Of course, ultimately I'm trying to get this whole thing into FDEP Albers
for my map.
-- John
----- Message from Tripp Corbin <tcorbin at keckwood.com> on Fri, 20 Jul 2007
09:22:43 -0400 -----
To: <shrug-L at lists.dep.state.fl.us>
Subject: shrug-l: Seats still available for ArcGIS classes in Aug
We still have a few seats available in our Introduction to ArcGIS I class
being held on August 20-21 at our office in Duluth GA. The cost is only
$750.00 per student. We have one seat left in our Introduction to ArcGIS II
class being held on August 22-24 at our office in Duluth GA. The cost for
that class is $1,100.00 per student. If you want to take both the cost is
only $1,750.00. For more information visit our website at www.keckwood.com
Tripp Corbin, MCP, CFM, GISP
Associate Vice President, GIS/Mapping
ESRI Authorized Instructor
Keck & Wood, Inc.
www.keckwood.com
(678) 417-4013
(678) 417-8785 fax
Keck & Wood, Inc offers instructor led and virtual training for ESRI's
ArcGIS & ArcView software.
Please visit www.keckwood.com for more information including a schedule of
upcoming classes.
----- Message from <Eric_Songer at URSCorp.com> on Fri, 20 Jul 2007 11:50:28
-0400 -----
To: "Sykes, John" <John.Sykes at dep.state.fl.us>
cc: <shrug-L at lists.dep.state.fl.us>
Subject: Re: shrug-l: Surveyors, AARRGGHH!!!
Ha,
It's common for surveyors data, especially of that vintage, to be measured
in feet and referenced to a local coordinate system. In the old days, if it
was measured in feet, then it was often called SPC in my experience.
I would make a 2 point world file and bring the CAD drawing back to the
space where you want it. Not an image world file, but one for CAD. Check
the ArcMap documentation for how to do it. A 2 point world file will scale
and rotate the data, which should be all you need to if the data were
really surveyed in the first place.
Now what was the purpose of Chapter 472? To protect the public by allowing
only Licensed surveyors do mapping, I believe. I don't feel safer....
I believe there is a 10,000 foot offset between SPC NAD27 and SPC NAD83. I
can't remember if it is east-west or north-south. Maybe Ronnie is reading
and can fill us in on the details. I always like reading his responses. You
can take a file of know projection and project it to SPC in both NAD27 and
NAD83 and see the difference.
Thanks,
Eric Songer
URS Corporation
1625 Summit Lake Drive
Tallahassee, FL 32317
Direct: 850.402.6327
Main: 800.842.9671 ext. 327
eric_songer at urscorp.com
This e-mail and any attachments are confidential. If you receive this
message in error or are not the intended recipient, you should not retain,
distribute, disclose or use any of this information and you should destroy
the e-mail and any attachments or copies.
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shrug-l: Surveyors,
AARRGGHH!!!
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I just received an AutoCAD file of a survey produced in the late 1980's.
Additional field work was done in 2004 and this revised survey is the CAD
file I have.
I assumed the survey work was done in State Plane Coordinates NAD83, but
when I created a projection file for this survey it ended up about 30 miles
west of the site when I let the file project on the fly!
So I went back and created a new projection file, this time establishing
the coordinates as State Plane Coordinates (SPC) NAD27. When I imported the
CAD drawing I immediately saw that the CAD drawing was coming out southwest
of where it should be by about 50 ft. I realized that the surveyor
apparently had taken a SPC NAD27 file and offset it by the correction
factor from NAD27 to NAD83 without taking into account the difference in
the offset that also exists between the two projections (I have been told
that this 30 mile offset was added to the SPCs to make if obvious when the
wrong projection was being used).
The problem is that, if I reproject the SPC NAD27 file to SPC NAD83, it
adds the offset between the two datums back in again!!! Short of getting
the surveyor to correct their file (not likely since the job was finished
in 2004) how do I get this error corrected???
By the way, I tried telling the PRJ file that the coordinates were SPC
NAD27 and the datum was NAD83, but that didn't work. Also, I found that the
reprojection tool in the toolbox doesn't work for CAD files.
Of course, ultimately I'm trying to get this whole thing into FDEP Albers
for my map.
-- John _______________________________________________
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