Ortho Projection Question

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Ortho Projection Question

cokrzys
I am trying to duplicate an ESRI "local" projection with Proj.4
parameters and can't quite get it worked out.  The ESRI custom
projection file has:

PROJCS["Twin_Creeks_Mine_Grid (Local)",
GEOGCS["GCS_North_American_1927",
DATUM["D_North_American_1927",SPHEROID["Clarke_1866",6378206.4,294.9786982]],
PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],
PROJECTION["Local"],
PARAMETER["False_Easting",14225.0],
PARAMETER["False_Northing",36603.0],
PARAMETER["Scale_Factor",1.0],
PARAMETER["Azimuth",0.0],
PARAMETER["Longitude_Of_Center",-117.183175],
PARAMETER["Latitude_Of_Center",41.217358],
UNIT["Foot_US",0.3048006096012192]]

The equivalent Proj.4 parameters I've setup are:

+proj=ortho +datum=NAD27 +lat_0=41.217358 +lon_0=-117.183175
+x_0=14225.0 +y_0=36603.0 +units=us-ft no_defs

I want to convert to lat-long WGS84 so I am going to this:

+proj=longlat +datum=WGS84 +no_defs no_defs

My input test point is:

x = 15768.1900000000 y = 65384.1600000000

In ESRI land I get back (lat-long): 41.160175 -117.177571

With Proj.4 I am getting: 41.0674232619472 -117.296349865729

I've also tried this with a couple of specific +to_wgs transformations
on the ESRI and Proj.4 side and still cannot get the conversions to
match.

This is all with Proj.4 Rel. 4.7.1, 23 September 2009.

What I'm wondering about is the ortho "projection" and if there is
maybe a better option to use?  I've searched around the web a bit and
read about concerns with ortho so also not sure if there is a proj
update beyond 4.7.1 that might help?  I know this whole kind of
direct-Cartesian conversion isn't the best thing, but generally stuck
just trying to match what Arc is doing.

Thanks for the help, Brian.
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Re: Ortho Projection Question

Noel Zinn (cc)
Brian,

If ESRI's PROJECTION["Local"] is also known as ESRI's "Local Cartesian",
then you'll need an ellipsoidal version of the orthographic projection to
match it.  I suspect that Proj.4's +proj=ortho is a spherical version of the
orthographic.

You make it difficult to test this by tossing in a transformation from NAD27
to WGS84 (+proj=longlat +datum=WGS84 +no_defs no_defs) with parameters
unknown to me.  Is this NADCON?  How about one problem at a time?  Can you
provide ESRI and Proj.4 lat/lon outputs in NAD27?

You can find the equations for the ellipsoidal orthographic here:
http://www.hydrometronics.com/downloads/Ellipsoidal%20Orthographic%20Projection.pdf

The inverse given in the link is iterative.  Charles Karney has provided a
closed inverse that has not yet been included in the linked paper.

Noel

Noel Zinn, Principal, Hydrometronics LLC
+1-832-539-1472 (office), +1-281-221-0051 (cell)
[hidden email] (email)
http://www.hydrometronics.com (website)

-----Original Message-----
From: Brian Krzys
Sent: Thursday, November 03, 2011 8:37 PM
To: [hidden email]
Subject: [Proj] Ortho Projection Question

I am trying to duplicate an ESRI "local" projection with Proj.4
parameters and can't quite get it worked out.  The ESRI custom
projection file has:

PROJCS["Twin_Creeks_Mine_Grid (Local)",
GEOGCS["GCS_North_American_1927",
DATUM["D_North_American_1927",SPHEROID["Clarke_1866",6378206.4,294.9786982]],
PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],
PROJECTION["Local"],
PARAMETER["False_Easting",14225.0],
PARAMETER["False_Northing",36603.0],
PARAMETER["Scale_Factor",1.0],
PARAMETER["Azimuth",0.0],
PARAMETER["Longitude_Of_Center",-117.183175],
PARAMETER["Latitude_Of_Center",41.217358],
UNIT["Foot_US",0.3048006096012192]]

The equivalent Proj.4 parameters I've setup are:

+proj=ortho +datum=NAD27 +lat_0=41.217358 +lon_0=-117.183175
+x_0=14225.0 +y_0=36603.0 +units=us-ft no_defs

I want to convert to lat-long WGS84 so I am going to this:

+proj=longlat +datum=WGS84 +no_defs no_defs

My input test point is:

x = 15768.1900000000 y = 65384.1600000000

In ESRI land I get back (lat-long): 41.160175 -117.177571

With Proj.4 I am getting: 41.0674232619472 -117.296349865729

I've also tried this with a couple of specific +to_wgs transformations
on the ESRI and Proj.4 side and still cannot get the conversions to
match.

This is all with Proj.4 Rel. 4.7.1, 23 September 2009.

What I'm wondering about is the ortho "projection" and if there is
maybe a better option to use?  I've searched around the web a bit and
read about concerns with ortho so also not sure if there is a proj
update beyond 4.7.1 that might help?  I know this whole kind of
direct-Cartesian conversion isn't the best thing, but generally stuck
just trying to match what Arc is doing.

Thanks for the help, Brian.
_______________________________________________
Proj mailing list
[hidden email]
http://lists.maptools.org/mailman/listinfo/proj 


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Re: Ortho Projection Question

Mikael Rittri
In reply to this post by cokrzys
In Proj.4, the x_0 and y_0 should be expressed in meters (unless you have an ellipsoid definition in feet, but the predefined ones are in meters).

I am not sure about ESRI, but I suspect that the False Easting and False Northing are expressed in US feet in this case. So you can try to convert them to meters for use in Proj.4.

Regards,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

4 nov 2011 kl. 02:58 skrev "Brian Krzys" <[hidden email]>:

> I am trying to duplicate an ESRI "local" projection with Proj.4
> parameters and can't quite get it worked out.  The ESRI custom
> projection file has:
>
> PROJCS["Twin_Creeks_Mine_Grid (Local)",
> GEOGCS["GCS_North_American_1927",
> DATUM["D_North_American_1927",SPHEROID["Clarke_1866",6378206.4,294.9786982]],
> PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],
> PROJECTION["Local"],
> PARAMETER["False_Easting",14225.0],
> PARAMETER["False_Northing",36603.0],
> PARAMETER["Scale_Factor",1.0],
> PARAMETER["Azimuth",0.0],
> PARAMETER["Longitude_Of_Center",-117.183175],
> PARAMETER["Latitude_Of_Center",41.217358],
> UNIT["Foot_US",0.3048006096012192]]
>
> The equivalent Proj.4 parameters I've setup are:
>
> +proj=ortho +datum=NAD27 +lat_0=41.217358 +lon_0=-117.183175
> +x_0=14225.0 +y_0=36603.0 +units=us-ft no_defs
>
> I want to convert to lat-long WGS84 so I am going to this:
>
> +proj=longlat +datum=WGS84 +no_defs no_defs
>
> My input test point is:
>
> x = 15768.1900000000 y = 65384.1600000000
>
> In ESRI land I get back (lat-long): 41.160175 -117.177571
>
> With Proj.4 I am getting: 41.0674232619472 -117.296349865729
>
> I've also tried this with a couple of specific +to_wgs transformations
> on the ESRI and Proj.4 side and still cannot get the conversions to
> match.
>
> This is all with Proj.4 Rel. 4.7.1, 23 September 2009.
>
> What I'm wondering about is the ortho "projection" and if there is
> maybe a better option to use?  I've searched around the web a bit and
> read about concerns with ortho so also not sure if there is a proj
> update beyond 4.7.1 that might help?  I know this whole kind of
> direct-Cartesian conversion isn't the best thing, but generally stuck
> just trying to match what Arc is doing.
>
> Thanks for the help, Brian.
> _______________________________________________
> Proj mailing list
> [hidden email]
> http://lists.maptools.org/mailman/listinfo/proj
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Re: Ortho Projection Question

insyzygy
A related question about +ortho:

Does it support azimuth angles other than 0.0?

Garret


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Mikael Rittri
Sent: 4-Nov-11 5:21 PM
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Ortho Projection Question

In Proj.4, the x_0 and y_0 should be expressed in meters (unless you
have an ellipsoid definition in feet, but the predefined ones are in
meters).

I am not sure about ESRI, but I suspect that the False Easting and False
Northing are expressed in US feet in this case. So you can try to
convert them to meters for use in Proj.4.

Regards,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

4 nov 2011 kl. 02:58 skrev "Brian Krzys" <[hidden email]>:

> I am trying to duplicate an ESRI "local" projection with Proj.4
> parameters and can't quite get it worked out.  The ESRI custom
> projection file has:
>
> PROJCS["Twin_Creeks_Mine_Grid (Local)",
> GEOGCS["GCS_North_American_1927",
> DATUM["D_North_American_1927",SPHEROID["Clarke_1866",6378206.4,294.978
> 6982]], PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],
> PROJECTION["Local"],
> PARAMETER["False_Easting",14225.0],
> PARAMETER["False_Northing",36603.0],
> PARAMETER["Scale_Factor",1.0],
> PARAMETER["Azimuth",0.0],
> PARAMETER["Longitude_Of_Center",-117.183175],
> PARAMETER["Latitude_Of_Center",41.217358],
> UNIT["Foot_US",0.3048006096012192]]
>
> The equivalent Proj.4 parameters I've setup are:
>
> +proj=ortho +datum=NAD27 +lat_0=41.217358 +lon_0=-117.183175
> +x_0=14225.0 +y_0=36603.0 +units=us-ft no_defs
>
> I want to convert to lat-long WGS84 so I am going to this:
>
> +proj=longlat +datum=WGS84 +no_defs no_defs
>
> My input test point is:
>
> x = 15768.1900000000 y = 65384.1600000000
>
> In ESRI land I get back (lat-long): 41.160175 -117.177571
>
> With Proj.4 I am getting: 41.0674232619472 -117.296349865729
>
> I've also tried this with a couple of specific +to_wgs transformations

> on the ESRI and Proj.4 side and still cannot get the conversions to
> match.
>
> This is all with Proj.4 Rel. 4.7.1, 23 September 2009.
>
> What I'm wondering about is the ortho "projection" and if there is
> maybe a better option to use?  I've searched around the web a bit and
> read about concerns with ortho so also not sure if there is a proj
> update beyond 4.7.1 that might help?  I know this whole kind of
> direct-Cartesian conversion isn't the best thing, but generally stuck
> just trying to match what Arc is doing.
>
> Thanks for the help, Brian.
> _______________________________________________
> Proj mailing list
> [hidden email]
> http://lists.maptools.org/mailman/listinfo/proj
_______________________________________________
Proj mailing list
[hidden email]
http://lists.maptools.org/mailman/listinfo/proj
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Re: Ortho Projection Question

insyzygy
Just poking about this request that equates proj's +ortho flag with ESRI's "Local Projection"

I would like to know if the +ortho flag supports rotation angles beween 0 and 180 so I can effectively rotate the cartesian axes so that the top of the projected map is not necessarily North.

If so, which version?

Thanks, Garret