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Mikael Rittri | 1 Oct 2008 13:22
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Some typos in the libproj4 manual

I think I have found some typos in the libproj4 manual.

Page 96, under the headline "Oblique Stereographic using intermediate sphere":

* Equation (7.36) says "k)0", but the parenthesis does not match anything.  I think it should have been "k_0"
in the LaTeX source, so that the text would be "k0", with the zero as a subscript. 
* Equation (7.37) reads

   chi = ( cos c ... )

but something is missing.  I looked in Snyder's book, and I think it should be

   chi = asin( cos c ...) 

(chi is that Greek letter that looks like a tall and narrow x, but isn't an x.) 

Page 78, table 6.1: Lambert Conformal Conic, in the general formula for rho, there is a numerator 

         tan^n( pi/4 + phi1/2)

but in the case phi1 = phi2, the analoguous numerator is written as 

         tan^n( pi/4 + phi1) / 2

Should not these numerators be identical?  They differ only in the placement of the ending parenthesis.  

Gerald Evenden wrote:
> Please, please, please.  Anyone finding errors in the previously reference
> manual please notify this group.  Thank-you.
(Continue reading)

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support.mn | 1 Oct 2008 16:08
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GeoTiff <-> Proj.4

Hello,

There is no general rule how to map GeoTiff GeoKeys to proj.4
parameters (or is there?) Every projection has it's own mapping?

Can I write "lat_ts" instead of "lat_0" ??

Is there "lon_ts"?

Here I have those keys I have found some mapping,
but how about the others. Must be different for each
projection?

----------

ProjLinearUnitSizeGeoKey	3077 in meters                 

ProjStdParallelGeoKey		3078 in GeogAngularUnit -> lat_1
ProjStdParallel2GeoKey	3079 in GeogAngularUnit -> lat_2
ProjOriginLongGeoKey		3080 in GeogAngularUnit  -> lon_0
ProjOriginLatGeoKey		3081 in GeogAngularUnit  -> lat_0
ProjFalseOriginLongGeoKey	3084 in GeogAngularUnit 
ProjFalseOriginLatGeoKey	3085 in GeogAngularUnit 
ProjCenterLongGeoKey	3088 in GeogAngularUnit 
ProjCenterLatGeoKey		3089 in GeogAngularUnit 

ProjFalseEastingGeoKey	3082 in ProjLinearUnits -> x_0
ProjFalseNorthingGeoKey	3083 in ProjLinearUnits -> y_0
ProjFalseOriginEastingGeoKey	3086 in ProjLinearUnits 
ProjFalseOriginNorthingGeoKey	3087 in ProjLinearUnits
(Continue reading)

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support.mn | 1 Oct 2008 16:20
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Re: GeoTiff <-> Proj.4

I resend the list:

ProjLinearUnitSizeGeoKey 3077 in meters

Angulars:

ProjStdParallelGeoKey 3078 in GeogAngularUnit -> lat_1
ProjStdParallel2GeoKey 3079 in GeogAngularUnit -> lat_2
ProjOriginLongGeoKey 3080 in GeogAngularUnit -> lon_0
ProjOriginLatGeoKey 3081 in GeogAngularUnit -> lat_0
ProjFalseOriginLongGeoKey 3084 in GeogAngularUnit -> ?
ProjFalseOriginLatGeoKey 3085 in GeogAngularUnit -> ?
ProjCenterLongGeoKey 3088 in GeogAngularUnit -> ?
ProjCenterLatGeoKey 3089 in GeogAngularUnit -> ?

Linears:

ProjFalseEastingGeoKey 3082 in ProjLinearUnits -> x_0
ProjFalseNorthingGeoKey 3083 in ProjLinearUnits -> y_0
ProjFalseOriginEastingGeoKey 3086 in ProjLinearUnits -> ?
ProjFalseOriginNorthingGeoKey 3087 in ProjLinearUnits -> ?
ProjCenterEastingGeoKey 3090 in ProjLinearUnits -> ?
ProjCenterNorthingGeoKey 3091 in ProjLinearUnits -> ?

Ratios:

ProjScaleAtOriginGeoKey 3092 in ratio -> k_0
ProjScaleAtCenterGeoKey 3093 in ratio -> ?

Others:
(Continue reading)

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Gerald I. Evenden | 1 Oct 2008 17:40
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Re: GeoTiff <-> Proj.4

On Wednesday 01 October 2008 10:08:12 am support.mn <at> elisanet.fi wrote:
> Hello,
>
> There is no general rule how to map GeoTiff GeoKeys to proj.4
> parameters (or is there?) Every projection has it's own mapping?
>
> Can I write "lat_ts" instead of "lat_0" ??

lat_ts denotes latitude of true scale while lat_0 generally refers to latitude 
of origin.  One should *never* assume that they create the same value.

> Is there "lon_ts"?

I have never used it. "Longitude of true scale" is a meaningless term.

> Here I have those keys I have found some mapping,
> but how about the others. Must be different for each
> projection?
>
> ----------
>
> ProjLinearUnitSizeGeoKey	3077 in meters
>
> ProjStdParallelGeoKey		3078 in GeogAngularUnit -> lat_1
> ProjStdParallel2GeoKey	3079 in GeogAngularUnit -> lat_2
> ProjOriginLongGeoKey		3080 in GeogAngularUnit  -> lon_0
> ProjOriginLatGeoKey		3081 in GeogAngularUnit  -> lat_0
> ProjFalseOriginLongGeoKey	3084 in GeogAngularUnit
> ProjFalseOriginLatGeoKey	3085 in GeogAngularUnit
> ProjCenterLongGeoKey	3088 in GeogAngularUnit
(Continue reading)

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Gerald I. Evenden | 1 Oct 2008 18:54
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Re: GeoTiff <-> Proj.4

On Wednesday 01 October 2008 10:20:41 am support.mn <at> elisanet.fi wrote:
> I resend the list:
>
> ProjLinearUnitSizeGeoKey 3077 in meters
>
> Angulars:
>
> ProjStdParallelGeoKey 3078 in GeogAngularUnit -> lat_1
> ProjStdParallel2GeoKey 3079 in GeogAngularUnit -> lat_2
> ProjOriginLongGeoKey 3080 in GeogAngularUnit -> lon_0
> ProjOriginLatGeoKey 3081 in GeogAngularUnit -> lat_0
> ProjFalseOriginLongGeoKey 3084 in GeogAngularUnit -> ?
> ProjFalseOriginLatGeoKey 3085 in GeogAngularUnit -> ?
> ProjCenterLongGeoKey 3088 in GeogAngularUnit -> ?
> ProjCenterLatGeoKey 3089 in GeogAngularUnit -> ?
>
> Linears:
>
> ProjFalseEastingGeoKey 3082 in ProjLinearUnits -> x_0
> ProjFalseNorthingGeoKey 3083 in ProjLinearUnits -> y_0
> ProjFalseOriginEastingGeoKey 3086 in ProjLinearUnits -> ?
> ProjFalseOriginNorthingGeoKey 3087 in ProjLinearUnits -> ?
> ProjCenterEastingGeoKey 3090 in ProjLinearUnits -> ?
> ProjCenterNorthingGeoKey 3091 in ProjLinearUnits -> ?
>
> Ratios:
>
> ProjScaleAtOriginGeoKey 3092 in ratio -> k_0
> ProjScaleAtCenterGeoKey 3093 in ratio -> ?
>
(Continue reading)

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Gerald I. Evenden | 1 Oct 2008 19:13
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Re: Some typos in the libproj4 manual

On Wednesday 01 October 2008 7:22:08 am Mikael Rittri wrote:
> I think I have found some typos in the libproj4 manual.
>
> Page 96, under the headline "Oblique Stereographic using intermediate
> sphere":
>
> * Equation (7.36) says "k)0", but the parenthesis does not match anything. 
> I think it should have been "k_0" in the LaTeX source, so that the text
> would be "k0", with the zero as a subscript. * Equation (7.37) reads
>
>    chi = ( cos c ... )
>
> but something is missing.  I looked in Snyder's book, and I think it should
> be
>
>    chi = asin( cos c ...)
>
> (chi is that Greek letter that looks like a tall and narrow x, but isn't an
> x.)
>
>
> Page 78, table 6.1: Lambert Conformal Conic, in the general formula for
> rho, there is a numerator
>
>          tan^n( pi/4 + phi1/2)
>
> but in the case phi1 = phi2, the analoguous numerator is written as
>
>          tan^n( pi/4 + phi1) / 2
>
(Continue reading)

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OvV_HN | 1 Oct 2008 21:55
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Re: Some typos in the libproj4 manual


----- Original Message ----- 
From: "Gerald I. Evenden" <geraldi.evenden <at> gmail.com>
Sent: Wednesday, October 01, 2008 7:13 PM
Subject: Re: [Proj] Some typos in the libproj4 manual

> On Wednesday 01 October 2008 7:22:08 am Mikael Rittri wrote:
>> I think I have found some typos in the libproj4 manual.

....

>> Gerald Evenden wrote:
>> > Please, please, please.  Anyone finding errors in the previously
>> > reference manual please notify this group.  Thank-you.

...

> Noted and changed.
>
> Thanks.
>
> I'm glad someone is doing this detailed reading.  Again, thanks.

I found some time ago several more errors (typos), omissions,
inconsistencies between the formulae and the actual code, and other
problems in the manual.
They were rather numerous and there wasn't any progress visible beyond the
"Preliminary Draft" version of March 2005.
So I chose to wait until a "real" version of the libproj4 manual would
appear.....
(Continue reading)

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Gerald I. Evenden | 1 Oct 2008 22:55
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Re: Some typos in the libproj4 manual

On Wednesday 01 October 2008 3:55:15 pm OvV_HN wrote:
> ----- Original Message -----
> From: "Gerald I. Evenden" <geraldi.evenden <at> gmail.com>
	...
> I found some time ago several more errors (typos), omissions,
> inconsistencies between the formulae and the actual code, and other
> problems in the manual.
> They were rather numerous and there wasn't any progress visible beyond the
> "Preliminary Draft" version of March 2005.
> So I chose to wait until a "real" version of the libproj4 manual would
> appear.....

I will put the current version on my site by this weekend.  Some corrections 
may have escaped due to my occasional  sloth.  My apologies in advance.

> If the math will be perfected, then the manual will become a valuable
> reference for cartographic projections in general.
>
> Another suggestion: give a numerical example with at least 5 decimals plus
> the exact command line code for each and every function.

What do you mean by "every function."  In term of precision of functions that 
depends upon what the function is returning.

What would be nice is for certified sample computations for all known grid 
systems.  Now that would be a *great* contribution.

In terms of forward projection precision, many sources only publish to the 
centimeter and I think someone on the list claimed that 100nm was sufficient 
for some applications.  Anyway ... .
(Continue reading)

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support.mn | 2 Oct 2008 07:29
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Re: GeoTiff <-> Proj.4

"Gerald I. Evenden" <geraldi.evenden <at> gmail.com> kirjoitti: 

> A question: is the "Proj" part of the above list referring to the proj we all 
> know and love?

These names are from the GeoTiff definition. Version 1.8.2 year 2000 is
probably the most recent. It defines the geoinformation tags for TIF files.
See

http://www.remotesensing.org/geotiff/spec/geotiffhome.html

> > Angulars:
> >
> > ProjStdParallelGeoKey 3078 in GeogAngularUnit -> lat_1
> > ProjStdParallel2GeoKey 3079 in GeogAngularUnit -> lat_2
> > ProjOriginLongGeoKey 3080 in GeogAngularUnit -> lon_0
> > ProjOriginLatGeoKey 3081 in GeogAngularUnit -> lat_0
> > ProjFalseOriginLongGeoKey 3084 in GeogAngularUnit -> ? 
> > ProjFalseOriginLatGeoKey 3085 in GeogAngularUnit -> ?
> > ProjCenterLongGeoKey 3088 in GeogAngularUnit -> ?
> > ProjCenterLatGeoKey 3089 in GeogAngularUnit -> ?

Do you have any idea what is the difference betwen "Origin"
"FalseOrigin" or "Center", or are they all the same?

> > Linears:
> >
> > ProjFalseEastingGeoKey 3082 in ProjLinearUnits -> x_0
> > ProjFalseNorthingGeoKey 3083 in ProjLinearUnits -> y_0
> > ProjFalseOriginEastingGeoKey 3086 in ProjLinearUnits -> ? (if used, maybe also x_0)
(Continue reading)

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Frank Warmerdam | 2 Oct 2008 08:05
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Re: GeoTiff <-> Proj.4

On Wed, Oct 1, 2008 at 4:08 PM,  <support.mn <at> elisanet.fi> wrote:
> Hello,
>
> There is no general rule how to map GeoTiff GeoKeys to proj.4
> parameters (or is there?) Every projection has it's own mapping?

Janne,

The page at:

  http://geotiff.maptools.org/proj_list/

represents a "best effort" attempt to document the
correlation between geotiff definitions and proj.4
(as well as EPSG and OGC WKT).

Best regards,
--

-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam <at> pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent
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