Differences between UTM Zone 30 (ED 50) projections

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Differences between UTM Zone 30 (ED 50) projections

Jelmer Baas
Hello,

I currently have a MapInfo file in UTM Zone 30 (ED 50) (EPSG: 23030) projection, which, after reprojection via OGR2OGR to EPSG:900913, moves a few meters East when compared to OSM.

Oddly enough, the EPSG file defines 23030 as
+proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +no_defs  <>

Yet, spatialreference.org (http://spatialreference.org/ref/epsg/ed50-utm-zone-30n/ ) defines it as
+proj=utm +zone=30 +ellps=intl +units=m +no_defs

For completeness, MapInfo PRO defines this projection system as:
UTM Zone 30 (ED 50)\p23030", 8, 28, 7, -3, 0, 0.9996, 500000, 0

My test:
Source From MapInfo 440151.086, 4494277.463
Mercator MapInfo -412840.28     4952824.92
CS2CS Simple[1] -412694.24       4952997.17 0.00 (so without the +towgs84 bit)
CS2CS towgs84[2] -412694.24       4952997.17 0.00
PostgreSQL 9.4[3] -412830.24       4952825.873
PostgreSQL Custom[4] -412694.23 4952997.16

From a developer at MapInfo I got a tip to try to include an accurate datum transform file, like NTV2_0.GSB, but CS2CS doesn't want to use this:
This file doesn't even exist:
cs2cs +nadgrids=blah.gsb +proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m
cs2cs +proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=blah.gsb
[no error, Process Monitor shows cs2cs not even trying to open the file]

[1] C:\OSGeo4W64\bin>cs2cs +proj=utm +zone=30 +ellps=intl +units=m  +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m
[2] C:\OSGeo4W64\bin>cs2cs +proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m
[3] select ST_AsText(ST_Transform(ST_GeomFromText('POINT(440151.086 4494277.463)', 23030), 900913))
[4] select ST_AsText(ST_Transform(ST_GeomFromText('POINT(440151.086 4494277.463)', 923030), 900913)) [5]
[5] INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 923030, 'epsg', 923030, '+proj=utm +zone=30 +ellps=intl +units=m +no_defs ', 'PROJCS["ED50 / UTM zone 30N",GEOGCS["ED50",DATUM["European_Datum_1950",SPHEROID["International 1924",6378388,297,AUTHORITY["EPSG","7022"]],AUTHORITY["EPSG","6230"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4230"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-3],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],AUTHORITY["EPSG","23030"],AXIS["Easting",EAST],AXIS["Northing",NORTH]]');

Can anyone tell me why there's a difference between the MapInfo PRO projection and the Proj.4 projection? And, hopefully, also a solution to correct this? Please note that I don't know whether MapInfo or Proj is at fault, I justk now that my data is drawn from MapInfo, where it's accurate compared to other data.

Thanks,
Jelmer

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Re: Differences between UTM Zone 30 (ED 50) projections

Andre Joost
Am 13.10.2016 um 10:07 schrieb Jelmer Baas:
> Hello,
>
> I currently have a MapInfo file in UTM Zone 30 (ED 50) (EPSG: 23030)
> projection, which, after reprojection via OGR2OGR to EPSG:900913,
> moves a few meters East when compared to OSM.

Looks like a datum shift issue, but kkep in mind that OSM is not
necessarily "exact".


>
> Oddly enough, the EPSG file defines 23030 as +proj=utm +zone=30
> +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +no_defs  <>

... using a mean shift value for whole Europe.

>
> Yet, spatialreference.org
> (http://spatialreference.org/ref/epsg/ed50-utm-zone-30n/ ) defines it
> as +proj=utm +zone=30 +ellps=intl +units=m +no_defs

... omitting the datum shift, which is surely wrong.

>
> For completeness, MapInfo PRO defines this projection system as: UTM
> Zone 30 (ED 50)\p23030", 8, 28, 7, -3, 0, 0.9996, 500000, 0

I'm not sure if this includes an explicit datum shift.


> From a developer at MapInfo I got a tip to try to include an accurate
> datum transform file, like NTV2_0.GSB, but CS2CS doesn't want to use
> this: This file doesn't even exist: cs2cs +nadgrids=blah.gsb
> +proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m
> +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0
> +y_0=0 +k=1.0 +units=m cs2cs +proj=utm +zone=30 +ellps=intl
> +towgs84=-87,-98,-121,0,0,0,0 +units=m +to +proj=merc +a=6378137
> +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m
> +nadgrids=blah.gsb [no error, Process Monitor shows cs2cs not even
> trying to open the file]

What datum shift grid did you use? the files I know are mainly from
national coordinate systems to WGS84.



>  Can anyone tell me why there's a difference between the MapInfo PRO
> projection and the Proj.4 projection? And, hopefully, also a solution
> to correct this? Please note that I don't know whether MapInfo or
> Proj is at fault, I justk now that my data is drawn from MapInfo,
> where it's accurate compared to other data.

The EPSG registry lists 42 valid datum shift parameter sets from ED50 to
WGS84, each with a different area of use. As written above, the values
in EPSG:23030 are a mean value, which can not provide centimeter accuracy.

HTH,
André Joost


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Re: Differences between UTM Zone 30 (ED 50) projections

Jelmer Baas
Hello Andre,

Thanks for the reply. I'll study your replies some more tomorrow, but I also continued experimenting, and found that the following yields nearly exactly the same results as MapInfo:
cs2cs +nadgrids=NTV2_0.GSB,BALEARES.gsb,PENINSULA.gsb +proj=utm +zone=30 +ellps=intl +units=m +to +proj=latlong +ellps=WGS84 +towgs84=0,0,0
[.]
pj_open_lib(BALEARES.gsb): call fopen(C:\OSGeo4W64\share\proj\BALEARES.gsb) - succeeded
NTv2 BALEARES 93x68: LL=(0.833333333,38) UR=(4.66666667,40.7916667)
pj_open_lib(PENINSULA.gsb): call fopen(C:\OSGeo4W64\share\proj\PENINSULA.gsb) - succeeded
NTv2 PENINSUL 259x161: LL=(-10.1833333,35.5555556) UR=(4.15,44.4444444)
NTv2 - loading grid PENINSUL
pj_open_lib(PENINSULA.gsb): call fopen(C:\OSGeo4W64\share\proj\PENINSULA.gsb) - succeeded
pj_apply_gridshift(): used PENINSUL
3d42'30.984"W   40d35'42.94"N 0.000

cs2cs +proj=latlong +ellps=WGS84 +towgs84=0,0,0 +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m
3d42'30.984"W   40d35'42.94"N 0.000
-412840.21      4952824.83 0.00

So when doing UTM Zone 30 ED 50 -> WGS84 -> Mercator, I get results I expect. Note that I'm using the .gsb files provided with MapInfo PRO, which answers you question below: the projection system as defined in MapInfo doesn't have the datum shift, but it uses the shift defined in its .gsb files.
Can I force this extra step in a proj wkt string? My goal is to have this working in PostgreSQL.

Using a fixed shift value could also work, since I'm only intested in Spain at the moment.

I'm not sure I understand this question of yours: " What datum shift grid did you use? the files I know are mainly from national coordinate systems to WGS84.". Care to eloborate?

Thanks,

Regards,
Jelmer

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Andre Joost
Sent: donderdag 13 oktober 2016 20:10
To: [hidden email]
Subject: Re: [Proj] Differences between UTM Zone 30 (ED 50) projections

Am 13.10.2016 um 10:07 schrieb Jelmer Baas:
> Hello,
>
> I currently have a MapInfo file in UTM Zone 30 (ED 50) (EPSG: 23030)
> projection, which, after reprojection via OGR2OGR to EPSG:900913,
> moves a few meters East when compared to OSM.

Looks like a datum shift issue, but kkep in mind that OSM is not
necessarily "exact".


>
> Oddly enough, the EPSG file defines 23030 as +proj=utm +zone=30
> +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +no_defs  <>

... using a mean shift value for whole Europe.

>
> Yet, spatialreference.org
> (http://spatialreference.org/ref/epsg/ed50-utm-zone-30n/ ) defines it
> as +proj=utm +zone=30 +ellps=intl +units=m +no_defs

... omitting the datum shift, which is surely wrong.

>
> For completeness, MapInfo PRO defines this projection system as: UTM
> Zone 30 (ED 50)\p23030", 8, 28, 7, -3, 0, 0.9996, 500000, 0

I'm not sure if this includes an explicit datum shift.


> From a developer at MapInfo I got a tip to try to include an accurate
> datum transform file, like NTV2_0.GSB, but CS2CS doesn't want to use
> this: This file doesn't even exist: cs2cs +nadgrids=blah.gsb
> +proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m
> +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0
> +y_0=0 +k=1.0 +units=m cs2cs +proj=utm +zone=30 +ellps=intl
> +towgs84=-87,-98,-121,0,0,0,0 +units=m +to +proj=merc +a=6378137
> +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m
> +nadgrids=blah.gsb [no error, Process Monitor shows cs2cs not even
> trying to open the file]

What datum shift grid did you use? the files I know are mainly from
national coordinate systems to WGS84.



>  Can anyone tell me why there's a difference between the MapInfo PRO
> projection and the Proj.4 projection? And, hopefully, also a solution
> to correct this? Please note that I don't know whether MapInfo or
> Proj is at fault, I justk now that my data is drawn from MapInfo,
> where it's accurate compared to other data.

The EPSG registry lists 42 valid datum shift parameter sets from ED50 to
WGS84, each with a different area of use. As written above, the values
in EPSG:23030 are a mean value, which can not provide centimeter accuracy.

HTH,
André Joost


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Re: Differences between UTM Zone 30 (ED 50) projections

Clifford J Mugnier
In reply to this post by Andre Joost
I find it hard to believe that ANY datum shift algorithm or data set is good to centimeters!

If a classical horizontal datum is involved; that’s impossible.  Two inertial datums … maybe.

European Datum 1950?  Not gonna happen.

Clifford J. Mugnier, CP,CMS,FASPRS
Chief of Geodesy,
Center for GeoInformatics (C4G)
266 ERAD (Research)
3335 PFT  (Academic)
Dept. of Civil & Environmental Engineering
LOUISIANA STATE UNIVERSITY
Baton Rouge, LA  70803
Research  225-578-4578
Academic   225-578-8536
Cell          225-328-8975









On 10/13/16, 1:09 PM, "[hidden email] on behalf of Andre Joost" <[hidden email] on behalf of [hidden email]> wrote:

>Am 13.10.2016 um 10:07 schrieb Jelmer Baas:
>> Hello,
>>
>> I currently have a MapInfo file in UTM Zone 30 (ED 50) (EPSG: 23030)
>> projection, which, after reprojection via OGR2OGR to EPSG:900913,
>> moves a few meters East when compared to OSM.
>
>Looks like a datum shift issue, but kkep in mind that OSM is not
>necessarily "exact".
>
>
>>
>> Oddly enough, the EPSG file defines 23030 as +proj=utm +zone=30
>> +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +no_defs  <>
>
>... using a mean shift value for whole Europe.
>
>>
>> Yet, spatialreference.org
>> (http://spatialreference.org/ref/epsg/ed50-utm-zone-30n/ ) defines it
>> as +proj=utm +zone=30 +ellps=intl +units=m +no_defs
>
>... omitting the datum shift, which is surely wrong.
>
>>
>> For completeness, MapInfo PRO defines this projection system as: UTM
>> Zone 30 (ED 50)\p23030", 8, 28, 7, -3, 0, 0.9996, 500000, 0
>
>I'm not sure if this includes an explicit datum shift.
>
>
>> From a developer at MapInfo I got a tip to try to include an accurate
>> datum transform file, like NTV2_0.GSB, but CS2CS doesn't want to use
>> this: This file doesn't even exist: cs2cs +nadgrids=blah.gsb
>> +proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m
>> +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0
>> +y_0=0 +k=1.0 +units=m cs2cs +proj=utm +zone=30 +ellps=intl
>> +towgs84=-87,-98,-121,0,0,0,0 +units=m +to +proj=merc +a=6378137
>> +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m
>> +nadgrids=blah.gsb [no error, Process Monitor shows cs2cs not even
>> trying to open the file]
>
>What datum shift grid did you use? the files I know are mainly from
>national coordinate systems to WGS84.
>
>
>
>>  Can anyone tell me why there's a difference between the MapInfo PRO
>> projection and the Proj.4 projection? And, hopefully, also a solution
>> to correct this? Please note that I don't know whether MapInfo or
>> Proj is at fault, I justk now that my data is drawn from MapInfo,
>> where it's accurate compared to other data.
>
>The EPSG registry lists 42 valid datum shift parameter sets from ED50 to
>WGS84, each with a different area of use. As written above, the values
>in EPSG:23030 are a mean value, which can not provide centimeter accuracy.
>
>HTH,
>André Joost
>
>
>_______________________________________________
>Proj mailing list
>[hidden email]
>http://lists.maptools.org/mailman/listinfo/proj
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Re: Differences between UTM Zone 30 (ED 50) projections

Andre Joost
In reply to this post by Jelmer Baas
Hello Jelmer,

Am 13.10.2016 um 20:36 schrieb Jelmer Baas:

>
> I'm not sure I understand this question of yours: " What datum shift
> grid did you use? the files I know are mainly from national
> coordinate systems to WGS84.". Care to eloborate?
>

I did not know that a grid shift file from ED50 to WGS84 exists. The one
you have is valid for Spain only.

<http://terrasit.gva.es/val/kb/canvi-sistema-referencia-ed50-etrs89-transformacio-coordinades-utm-ed50-utm-etrs89-utilitzant-lli>
should help you on the way (I guess you understand Spanish better than I
do).


ftp://ftp.rgan.navarra.es/docs/Rejilla_NTv2/Spain/ should contain the
gsb files for those who have no access to mapinfo.


HTH,
André Joost

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Re: Differences between UTM Zone 30 (ED 50) projections

Jelmer Baas
In reply to this post by Clifford J Mugnier
The difference between MapInfo Pro and Proj4, when both using the datum shift file:
MapInfo -412840.21       4952824.83
Proj -412840.28         4952824.92
Proj[1] -412840.21       4952824.84
That's only a few centimers, which is acceptable for my purpose.

When removing the datum shift file from MapInfo, these are the results:
Proj -412830.24       4952825.87
PostgreSQL -412830.24         4952825.873
MapInfo -412830.25 4952825.87

I'd say that's spot-on :)

[1] cs2cs +nadgrids=NTV2_0.GSB,BALEARES.gsb,PENINSULA.gsb +init=epsg:23030 +to +init=epsg:3857

I've now added the following to my epsg file:
<923030> +nadgrids=BALEARES.gsb,PENINSULA.gsb +proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +no_defs  <>

Thanks.

Regards,
Jelmer Baas
Speer IT B.V.


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Clifford J Mugnier
Sent: donderdag 13 oktober 2016 20:55
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Differences between UTM Zone 30 (ED 50) projections

I find it hard to believe that ANY datum shift algorithm or data set is good to centimeters!

If a classical horizontal datum is involved; that’s impossible.  Two inertial datums … maybe.

European Datum 1950?  Not gonna happen.

Clifford J. Mugnier, CP,CMS,FASPRS
Chief of Geodesy,
Center for GeoInformatics (C4G)
266 ERAD (Research)
3335 PFT  (Academic)
Dept. of Civil & Environmental Engineering
LOUISIANA STATE UNIVERSITY
Baton Rouge, LA  70803
Research  225-578-4578
Academic   225-578-8536
Cell          225-328-8975









On 10/13/16, 1:09 PM, "[hidden email] on behalf of Andre Joost" <[hidden email] on behalf of [hidden email]> wrote:

>Am 13.10.2016 um 10:07 schrieb Jelmer Baas:
>> Hello,
>>
>> I currently have a MapInfo file in UTM Zone 30 (ED 50) (EPSG: 23030)
>> projection, which, after reprojection via OGR2OGR to EPSG:900913,
>> moves a few meters East when compared to OSM.
>
>Looks like a datum shift issue, but kkep in mind that OSM is not
>necessarily "exact".
>
>
>>
>> Oddly enough, the EPSG file defines 23030 as +proj=utm +zone=30
>> +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m +no_defs  <>
>
>... using a mean shift value for whole Europe.
>
>>
>> Yet, spatialreference.org
>> (http://spatialreference.org/ref/epsg/ed50-utm-zone-30n/ ) defines it
>> as +proj=utm +zone=30 +ellps=intl +units=m +no_defs
>
>... omitting the datum shift, which is surely wrong.
>
>>
>> For completeness, MapInfo PRO defines this projection system as: UTM
>> Zone 30 (ED 50)\p23030", 8, 28, 7, -3, 0, 0.9996, 500000, 0
>
>I'm not sure if this includes an explicit datum shift.
>
>
>> From a developer at MapInfo I got a tip to try to include an accurate
>> datum transform file, like NTV2_0.GSB, but CS2CS doesn't want to use
>> this: This file doesn't even exist: cs2cs +nadgrids=blah.gsb
>> +proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 +units=m
>> +to +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0
>> +y_0=0 +k=1.0 +units=m cs2cs +proj=utm +zone=30 +ellps=intl
>> +towgs84=-87,-98,-121,0,0,0,0 +units=m +to +proj=merc +a=6378137
>> +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m
>> +nadgrids=blah.gsb [no error, Process Monitor shows cs2cs not even
>> trying to open the file]
>
>What datum shift grid did you use? the files I know are mainly from
>national coordinate systems to WGS84.
>
>
>
>>  Can anyone tell me why there's a difference between the MapInfo PRO
>> projection and the Proj.4 projection? And, hopefully, also a solution
>> to correct this? Please note that I don't know whether MapInfo or
>> Proj is at fault, I justk now that my data is drawn from MapInfo,
>> where it's accurate compared to other data.
>
>The EPSG registry lists 42 valid datum shift parameter sets from ED50 to
>WGS84, each with a different area of use. As written above, the values
>in EPSG:23030 are a mean value, which can not provide centimeter accuracy.
>
>HTH,
>André Joost
>
>
>_______________________________________________
>Proj mailing list
>[hidden email]
>http://lists.maptools.org/mailman/listinfo/proj
_______________________________________________
Proj mailing list
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http://lists.maptools.org/mailman/listinfo/proj
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