[Proj] Correction of definition of CRS EPSG 5456 and 5457

Mon Jan 22 04:42:15 PST 2018

Hi Eduardo,

you can simply run a couple of tests using cs2cs.

Put "-85 11" in a file named CRN.txt, and the following in a batch file:

echo epsg4326-epsg5456 >out.txt
cs2cs +init=epsg:4326 +to +init=epsg:5456  -f "%%.3f" CRN.txt >>out.txt

echo 5456-5470 >>out.txt
cs2cs +init=epsg:4326  +to +proj=lcc +lat_1=10.46666666666667 
+lat_0=10.46666666666667 +lon_0=-84.33333333333333 +k_0=0.99995696 
+x_0=500000 +y_0=271820.522 +ellps=clrk66 
+towgs84=213.11,9.37,-74.95,0,0,0,0 +units=m +no_defs  +units=m +no_defs 
-f "%%.3f" CRN.txt >>out.txt

echo 5456-5473 (deprecated) >>out.txt
cs2cs +init=epsg:4326  +to +proj=lcc +lat_1=10.46666666666667 
+lat_0=10.46666666666667 +lon_0=-84.33333333333333 +k_0=0.99995696 
+x_0=500000 +y_0=271820.522 +ellps=clrk66 
+towgs84=213.116,9.358,-74.946,1.14e-05,-2.98e-07,3.1e-05,-5.22 +units=m 
+no_defs -f "%%.3f" CRN.txt >>out.txt

echo 5456-5474 (deprecated) >>out.txt
cs2cs +init=epsg:4326  +to +proj=lcc +lat_1=10.46666666666667 
+lat_0=10.46666666666667 +lon_0=-84.33333333333333 +k_0=0.99995696 
+x_0=500000 +y_0=271820.522 +ellps=clrk66 
+towgs84=205.435,-29.099,292.202,0,0,0,0 +units=m +no_defs  -f "%%.3f" 
CRN.txt >>out.txt

echo 5456-6889 >>out.txt
cs2cs +init=epsg:4326  +to +proj=lcc +lat_1=10.46666666666667 
+lat_0=10.46666666666667 +lon_0=-84.33333333333333 +k_0=0.99995696 
+x_0=500000 +y_0=271820.522 +ellps=clrk66 
+towgs84=213.11,9.37,-74.95,0,0,0,0 +units=m +no_defs  -f "%%.3f" 
CRN.txt >>out.txt

echo 5456-6891 >>out.txt
cs2cs +init=epsg:4326  +to +proj=lcc +lat_1=10.46666666666667 
+lat_0=10.46666666666667 +lon_0=-84.33333333333333 +k_0=0.99995696 
+x_0=500000 +y_0=271820.522 +ellps=clrk66 +towgs84=205,96,-98,0,0,0,0 
+units=m +no_defs  -f "%%.3f" CRN.txt >>out.txt

echo 5456(lcc from Rodriguez via proj.4-ML) >>out.txt
cs2cs +init=epsg:4326  +to +proj=lcc +lat_0=10.46666666666667 
+lat_1=9.933333333 +lat_2=11 +lon_0=-84.3333333333 +k_0=0.99995696 
+x_0=500000 +y_0=271820.522 +ellps=clrk66 +towgs84=205,96,-98,0,0,0,0 
+units=m +no_defs -f "%%.3f" CRN.txt >>out.txt

echo 5456(lcc+towgs84 from Rodriguez via proj.4-ML) >>out.txt
cs2cs +init=epsg:4326  +to +proj=lcc +lat_0=10.46666666666667 
+lat_1=9.933333333 +lat_2=11 +lon_0=-84.3333333333 +k_0=0.99995696 
+x_0=500000 +y_0=271820.522 +ellps=clrk66 
+towgs84=213.116,9.358,-74.946,1.140,-2.980,3.100,-5.22 +units=m 
+no_defs -f "%%.3f" CRN.txt >>out.txt

The results are:

epsg4326-epsg5456
426928.564	331056.442 34.278
5456-5470
426928.019	331050.421 -55.529
5456-5473 (deprecated)
426928.014	331050.378 -22.252
5456-5474 (deprecated)
426938.268	330697.171 -162.546
5456-6889
426928.019	331050.421 -55.529
5456-6891
426928.564	331056.442 34.278
5456(lcc from Rodriguez via proj.4-ML)
426931.711	331053.893 34.278
5456(lcc+towgs84 from Rodriguez via proj.4-ML)
426855.097	331075.075 -22.217

I have no clue what values are "correct", since I have not found any 
sample coordinates in both systems.

My best resource available online is

https://dialnet.unirioja.es/descarga/articulo/5381246.pdf
http://www.revistas.una.ac.cr/index.php/uniciencia/article/download/5930/5822

from Dörries and Rodriguez (obviously not you).

Another online resource is http://epsg.io/5456 , which contains also 
transformations 5473 and 5474 that are deprecated by EPSG. I added them 
to my test.

Note that transformation 6889 from the EPSG registry uses a 10-parameter 
transformation (7parms on a point on the Earth's surface with 3 
coordinates), which can not be used inside PROJ.4. so you really have 
the choice between 5470 and 6891. EPSG.io seems to fall back to the 
transformation 5470.

The paramaters in your first posting seem to be an adaptation of the 
10-parms, omitting the anchor point and the exponents.

Even the lcc1 vs lcc2 yields different results, but I have not looked 
into that.

HTH,
Andre Joost

Am 22.01.18 um 03:51 schrieb Eduardo Rojas Rodríguez:
> Hi Andre
>
> sorry for bothering you again
>
> I have read extensively all the information you have given me and I have
> come to the following conclusions:
>
> 1. according to
> https://gis.stackexchange.com/questions/253475/results-of-layers-created-with-a-custom-crs-are-loaded-with-a-generated-crs-in-q/254087#254087
> and
> http://geotiff.maptools.org/proj_list/lambert_conic_conformal_2sp.html
>
> By having proj LCC 1SP with a scale factor is basically the same as LCC 2SP.
> so the definition within PROJ4
> + proj = lcc + lat_1 = 10.46666666666667 + lat_0 = 10.46666666666667 + lon_0
> = -84.33333333333333 + k_0 = 0.99995696 + x_0 = 500000 + y_0 = 271820.522 +
> ellps = clrk66 + towgs84 = 205.96, -98.0.0.0.0 + units = m + no_defs
>
> is correct since it determines lat_1 equal to lat_0
>
> is this correct?
>
> 1. Regarding the "toWGS84" + towgs84 = 205.96, -98.0,0.0.0
> is a concatenation (via NAD27) of the transformations 6888 and 1171 imported
> from GDAL when using this transformation I get a displacement of 2mm
>
> 3. + towgs84 = 213.116,9.358, -74.946 are within the transformation EPSG ::
> 5470 Coordinate Transformation [Ocotepeque 1935 to WGS 84 (1)] which is more
> general and I get displacements of 8 meters
>
> As far as I can deduce, the definition is adequate both when using LCC1
> which is equal to LCC2 with the scale factor.
>
> the only thing then is to ask the EPSG for a transformation of EPSG :: 5470
> Coordinate Transformation [Ocotepeque 1935 to WGS 84 (1) more presiding
> using 7 parameters. maybe?
>
>
> I would like to know what you think of my conclusions, so I can tell you how
> much I have learned from PROJ4 and EPSG.
>
> Thank you very much for all the help and everything I've learned
>
>
>
> -----
> Eduardo Rojas Rodríguez
> Analista en SIG
> Soluciones en Tecnologías
> Tel: 506 2505-5453
> eduardo.rojas at soltig.net
> http://soltig.net
>
>
> --
> Sent from: http://osgeo-org.1560.x6.nabble.com/PROJ-4-f3840930.html
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