[Proj] Krovak again

Mikael Rittri Mikael.Rittri at carmenta.com
Wed Aug 17 05:40:52 EST 2011

Hello Irwin.

> What is EPSG 102067?  It's not in the EPSG database. 

True, there is no such thing as EPSG:102067. Someone must
have meant ESRI:102067, which is called Krovak East North.


There are basically two families of Czech-and-Slovakian
Krovak instances.  

  * In the "classical" ones, for example S-JTSK / Krovak (EPSG:5513), 
    the first axis (X) goes south, and the second axis Y goes west.

  * In the "GIS" variants, for example ESRI:102067, the
    axes go east and north, which is necessary in many 
    GIS systems. They should have the phrase "East North"
    in their name. 

A property they all share is that the grid origin 
(where both projected coordinates are zero) is at the 
oblique cone apex between Helsinki and Tallinn,
northeast of Czech-and-Slovakia.    

This means that in the "classical" (South West) variants,
all projected coordinates are positive in Czech-and-Slovakia,
but in the GIS variants, they are negative there. 

You wrote:

> The national Inspire Czech Geoportal site shows 
> negative values increasing to the south and west

I don't understand that. So I hope that when you say 
"negative values increasing" to the south and west, 
you mean that the values become _more_ negative, 
that is: the values decrease, but their absolute 
values increase, towards south and west.

It took many years for EPSG to add GIS-Krovak variants,
so the ESRI codes for some Krovak variants have become 

   ESRI:102065, S-JTSK Krovak
   ESRI:102066, S-JTSK Ferro Krovak East North
   ESRI:102067, S-JTSK Krovak East North

These are equivalent, as far as I know, to the recent EPSG entries

   EPSG:5513, S-JTSK / Krovak
   EPSG:5221, S-JTSK (Ferro) / Krovak East North
   EPSG:5514, S-JTSK / Krovak East North

respectively. Then, you have also the oldest variant

   EPSG:2065, S-JTSK (Ferro) / Krovak.

Furthermore, Czech authorities have introduced a modified 
version of the S-JTSK datum, which is called S-JTSK/05. 
With this modified datum, you must use a "Modified Krovak" 
projection, which somehow compensates for distortions in 
the datum realisation (I don't understand the design or purpose,
but I believe the modifications do not change coordinates 
more than about 1 meter). There are four EPSG entries based 
on S-JTSK/05: 
    EPSG:5224, 5225, 5515 and 5516. 

Best Regards,

Mikael Rittri

-----Original Message-----
From: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] On Behalf Of Irwin Scollar
Sent: den 17 augusti 2011 10:44
To: proj at lists.maptools.org
Subject: [Proj] Krovak again

The Czech GeoPortal site:

http://geoportal.cuzk.cz  (COSMC)

shows positive coordinates (Krovak) increasing to the south and the west when the mouse cursor is moved over a map or an orthophoto.

A map area centered on Prague on the COSMC site automatically shows the bounding box coordinates as negative numbers in the search field of the web browser.


The national Inspire Czech Geoportal site shows negative values increasing to the south and west in the lower left corner on mouse movement.


Which Krovak variant shown in OGP Publication 373-7.2 p 25ff is involved here or is this yet another variant?

What is EPSG 102067?  It's not in the EPSG database.

Irwin Scollar

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