[Proj] OT: Geotrans's Neys Projection - Modified Lambert Conformal Conic

[proj-admin at remotesensing.org]

The only gotcha might seem to be the near polar spec of one of the
secant latitudes at 89d59'59 but [l]proj seems to handle this OK.  In 
fact,
one can spec it to 59.999" and still not blow it; but 90d even does 
cause
failure.  This does not mean that all is OK in the computations due to
possible loss of significance or other computational hassles.

The spec is not perfect as there is a gore that is about 12km wide 
opposite
the CM.  That is, the cone is not closed.

It would be interesting to compare the scale error with the polar 
stereographic
which, IMHO, would be the preferred projection.

I can see why this is not mentioned anywhere else.

On Apr 19, 2004, at 2:07 PM, proj-admin at remotesensing.org wrote:
>
> The GeoTrans documentation says:
>
> "A.1.25 NEY?S (MODIFIED LAMBERT CONFORMAL CONIC) PROJECTION
> The Ney's (Modified Lambert Conformal Conic) projection is a conformal
> projection in which the projected parallels are expanded slightly to 
> form
> complete concentric circles centered at the pole. As shown in Figure 
> A-27,
> the projected meridians are radii of concentric circles that meet at 
> the
> pole. Ney's is a limiting form of the Lambert Conformal Conic. There 
> are
> two parallels, called standard parallels, along which the point scale
> factor is one. One parallel is at either ±71 or ±74 degrees. The other
> parallel is at ±89 59 59.0 degrees, depending on which hemisphere the 
> first
> parallel is in.
> Ney's (Modified Lambert Conformal Conic) is used near the poles. Scale
> distortion is small 25° to 30° from the pole. Distortion rapidly 
> increases
> beyond this.
> The Easting\X and Northing\Y coordinates range from -40,000,000 to
> 40,000,000.
>
>
> "?    1st Standard Parallel ? A latitude value that specifies one of 
> the
> two the parallels where the point scale factor is 1.0.  The 1st 
> Standard
> Parallel is either ?71 or ?74 degrees. The hemisphere of the Origin
> Latitude determines the sign.
>
> ?     2nd Standard Parallel ? A latitude value that specifies one of 
> the
> two the parallels where the point scale factor is 1.0.  The 2nd 
> Standard
> Parallel is fixed at ?89 59 59.0 degrees. The hemisphere of the Origin
> Latitude determines the sign."
>
> Other than these specifics regarding the choice for the Standard 
> Parallels,
> the Ney's Projection is a standard Lambert Conformal Conic in a secant
> (POLAR) case.
>
> Note that: "Ney?s (Modified Lambert Conformal Conic) projection 
> coordinates
> consist of two fields labeled Easting/X and Northing/Y.  The legal 
> values
> for the Easting/X and the Northing/Y fields are optionally signed real
> values, with up to three decimal places, in meters.  The coordinates 
> must
> designate a point that is located within the boundaries of the 
> specified
> Ney?s (Modified Lambert Conformal Conic) projection."
>
> Ney's Projection is a POLAR (aspect) Projection.
>
> GeoTrans does have its warts, but this explanation is crystal-clear to 
> a
> practitioner in the field.
>
> Cliff Mugnier
> LOUISIANA STATE UNIVERSITY
>
> -----------------------------------
>
> I cannot find any reference to "Neys" projection in my references or
> bibiography
> listings.
>
> Snyder mentions some alternative Lambert Conics; one based upon "Gauss
> projection."  Perhaps using the conformal projection to the sphere?
> But Neys
> never appears in any index.  Perhaps Russian, but the name does not
> sound
> like a Russian name.
>
> The NIMA GeoTrans stuff is completely incomprehensible so I was not 
> able
> to verify the location of any related material in the remotesensing
> distribution.
>
> If anyone can supply a reference I would be glad to look into it.
>
> On Apr 18, 2004, at 9:24 PM, proj-admin at remotesensing.org wrote:
>
>> Hello All,
>> Anyone familiar with the Neys projection found in the GeoTrans 
>> package?
>>
>> It is stated as being a "Modified Lambert Conformal Conic", but I
>> could not
>> find any further information in my reference books or online.
>> Or is there a more known name for this? Is this supported by proj4?
>>
>> Just any information on this will do.
>>
>> Best regards,
>> Paul.
> _____________________________________
> Jerry and the low riders: Daisy Mae and Joshua
>
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_____________________________________
Jerry and the low riders: Daisy Mae and Joshua
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