/******************************************************************************
 *
 * Project:  OpenGIS Simple Features Reference Implementation
 * Purpose:  OGRSpatialReference translation to/from USGS georeferencing
 *           information (used in GCTP package).
 * Author:   Andrey Kiselev, dron@ak4719.spb.edu
 *
 ******************************************************************************
 * Copyright (c) 2004, Andrey Kiselev <dron@ak4719.spb.edu>
 * Copyright (c) 2008-2009, Even Rouault <even dot rouault at spatialys.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ****************************************************************************/

#include "cpl_port.h"
#include "ogr_srs_api.h"

#include <cmath>
#include <cstddef>

#include "cpl_conv.h"
#include "cpl_csv.h"
#include "cpl_error.h"
#include "cpl_string.h"
#include "ogr_core.h"
#include "ogr_p.h"
#include "ogr_spatialref.h"

/************************************************************************/
/*  GCTP projection codes.                                              */
/************************************************************************/

constexpr long GEO = 0L;      // Geographic
constexpr long UTM = 1L;      // Universal Transverse Mercator (UTM)
constexpr long SPCS = 2L;     // State Plane Coordinates
constexpr long ALBERS = 3L;   // Albers Conical Equal Area
constexpr long LAMCC = 4L;    // Lambert Conformal Conic
constexpr long MERCAT = 5L;   // Mercator
constexpr long PS = 6L;       // Polar Stereographic
constexpr long POLYC = 7L;    // Polyconic
constexpr long EQUIDC = 8L;   // Equidistant Conic
constexpr long TM = 9L;       // Transverse Mercator
constexpr long STEREO = 10L;  // Stereographic
constexpr long LAMAZ = 11L;   // Lambert Azimuthal Equal Area
constexpr long AZMEQD = 12L;  // Azimuthal Equidistant
constexpr long GNOMON = 13L;  // Gnomonic
constexpr long ORTHO = 14L;   // Orthographic
// constexpr long GVNSP  = 15L;  // General Vertical Near-Side Perspective
constexpr long SNSOID = 16L;  // Sinusiodal
constexpr long EQRECT = 17L;  // Equirectangular
constexpr long MILLER = 18L;  // Miller Cylindrical
constexpr long VGRINT = 19L;  // Van der Grinten
constexpr long HOM = 20L;     // (Hotine) Oblique Mercator
constexpr long ROBIN = 21L;   // Robinson
// constexpr long SOM    = 22L;  // Space Oblique Mercator (SOM)
// constexpr long ALASKA = 23L;  // Alaska Conformal
// constexpr long GOODE  = 24L;  // Interrupted Goode Homolosine
constexpr long MOLL = 25L;  // Mollweide
// constexpr long IMOLL  = 26L;  // Interrupted Mollweide
// constexpr long HAMMER = 27L;  // Hammer
constexpr long WAGIV = 28L;   // Wagner IV
constexpr long WAGVII = 29L;  // Wagner VII
// constexpr long OBEQA  = 30L;  // Oblated Equal Area
// constexpr long ISINUS1 = 31L; // Integerized Sinusoidal Grid (the same as 99)
// constexpr long CEA    = 97L;  // Cylindrical Equal Area (Grid corners set
// in meters for EASE grid)
// constexpr long BCEA   = 98L;  // Cylindrical Equal Area (Grid corners set
// in DMS degs for EASE grid)
// constexpr long ISINUS = 99L;  // Integerized Sinusoidal Grid
// (added by Raj Gejjagaraguppe ARC for MODIS)

/************************************************************************/
/*  GCTP ellipsoid codes.                                               */
/************************************************************************/

constexpr long CLARKE1866 = 0L;
// constexpr long CLARKE1880         = 1L;
// constexpr long BESSEL             = 2L;
// constexpr long INTERNATIONAL1967  = 3L;
// constexpr long INTERNATIONAL1909  = 4L;
// constexpr long WGS72              = 5L;
// constexpr long EVEREST            = 6L;
// constexpr long WGS66              = 7L;
constexpr long GRS1980 = 8L;
// constexpr long AIRY               = 9L;
// constexpr long MODIFIED_EVEREST   = 10L;
// constexpr long MODIFIED_AIRY      = 11L;
constexpr long WGS84 = 12L;
// constexpr long SOUTHEAST_ASIA     = 13L;
// constexpr long AUSTRALIAN_NATIONAL= 14L;
// constexpr long KRASSOVSKY         = 15L;
// constexpr long HOUGH              = 16L;
// constexpr long MERCURY1960        = 17L;
// constexpr long MODIFIED_MERCURY   = 18L;
// constexpr long SPHERE             = 19L;

/************************************************************************/
/*  Correspondence between GCTP and EPSG ellipsoid codes.               */
/************************************************************************/

constexpr int aoEllips[] = {
    7008,  // Clarke, 1866 (NAD1927)
    7034,  // Clarke, 1880
    7004,  // Bessel, 1841
    0,     // FIXME: New International, 1967 --- skipped
    7022,  // International, 1924 (Hayford, 1909) XXX?
    7043,  // WGS, 1972
    7042,  // Everest, 1830
    7025,  // FIXME: WGS, 1966
    7019,  // GRS, 1980 (NAD1983)
    7001,  // Airy, 1830
    7018,  // Modified Everest
    7002,  // Modified Airy
    7030,  // WGS, 1984 (GPS)
    0,     // FIXME: Southeast Asia --- skipped
    7003,  // Australian National, 1965
    7024,  // Krassovsky, 1940
    7053,  // Hough
    0,     // FIXME: Mercury, 1960 --- skipped
    0,     // FIXME: Modified Mercury, 1968 --- skipped
    7047,  // Sphere, rad 6370997 m (normal sphere)
    7006,  // Bessel, 1841 (Namibia)
    7016,  // Everest (Sabah & Sarawak)
    7044,  // Everest, 1956
    7056,  // Everest, Malaysia 1969
    7018,  // Everest, Malay & Singapr 1948
    0,     // FIXME: Everest, Pakistan --- skipped
    7022,  // Hayford (International 1924) XXX?
    7020,  // Helmert 1906
    7021,  // Indonesian, 1974
    7036,  // South American, 1969
    0      // FIXME: WGS 60 --- skipped
};

#define NUMBER_OF_ELLIPSOIDS static_cast<int>(CPL_ARRAYSIZE(aoEllips))

/************************************************************************/
/*                         OSRImportFromUSGS()                          */
/************************************************************************/

/**
 * \brief Import coordinate system from USGS projection definition.
 *
 * This function is the same as OGRSpatialReference::importFromUSGS().
 */
OGRErr OSRImportFromUSGS(OGRSpatialReferenceH hSRS, long iProjsys, long iZone,
                         double *padfPrjParams, long iDatum)

{
    VALIDATE_POINTER1(hSRS, "OSRImportFromUSGS", OGRERR_FAILURE);

    return OGRSpatialReference::FromHandle(hSRS)->importFromUSGS(
        iProjsys, iZone, padfPrjParams, iDatum);
}

static double OGRSpatialReferenceUSGSUnpackNoOp(double dfVal)
{
    return dfVal;
}

static double OGRSpatialReferenceUSGSUnpackRadian(double dfVal)
{
    return dfVal * 180.0 / M_PI;
}

/************************************************************************/
/*                          importFromUSGS()                            */
/************************************************************************/

/**
\brief Import coordinate system from USGS projection definition.

This method will import projection definition in style, used by USGS GCTP
software. GCTP operates on angles in packed DMS format (see
CPLDecToPackedDMS() function for details), so all angle values (latitudes,
longitudes, azimuths, etc.) specified in the padfPrjParams array should
be in the packed DMS format, unless bAnglesInPackedDMSFormat is set to FALSE.
 *
This function is the equivalent of the C function OSRImportFromUSGS().
Note that the bAnglesInPackedDMSFormat parameter is only present in the C++
method. The C function assumes bAnglesInPackedFormat = TRUE.

@param iProjSys Input projection system code, used in GCTP.

@param iZone Input zone for UTM and State Plane projection systems. For
Southern Hemisphere UTM use a negative zone code. iZone ignored for all
other projections.

@param padfPrjParams Array of 15 coordinate system parameters. These
parameters differs for different projections.

\verbatim
Projection Transformation Package Projection Parameters:

----------------------------------------------------------------------------
                        |                    Array Element
 Code & Projection Id   |---------------------------------------------------
                        |   0  |   1  |  2   |  3   |   4   |    5    |6 | 7
----------------------------------------------------------------------------
 0 Geographic           |      |      |      |      |       |         |  |
 1 U T M                |Lon/Z |Lat/Z |      |      |       |         |  |
 2 State Plane          |      |      |      |      |       |         |  |
 3 Albers Equal Area    |SMajor|SMinor|STDPR1|STDPR2|CentMer|OriginLat|FE|FN
 4 Lambert Conformal C  |SMajor|SMinor|STDPR1|STDPR2|CentMer|OriginLat|FE|FN
 5 Mercator             |SMajor|SMinor|      |      |CentMer|TrueScale|FE|FN
 6 Polar Stereographic  |SMajor|SMinor|      |      |LongPol|TrueScale|FE|FN
 7 Polyconic            |SMajor|SMinor|      |      |CentMer|OriginLat|FE|FN
 8 Equid. Conic A       |SMajor|SMinor|STDPAR|      |CentMer|OriginLat|FE|FN
   Equid. Conic B       |SMajor|SMinor|STDPR1|STDPR2|CentMer|OriginLat|FE|FN
 9 Transverse Mercator  |SMajor|SMinor|Factor|      |CentMer|OriginLat|FE|FN
10 Stereographic        |Sphere|      |      |      |CentLon|CenterLat|FE|FN
11 Lambert Azimuthal    |Sphere|      |      |      |CentLon|CenterLat|FE|FN
12 Azimuthal            |Sphere|      |      |      |CentLon|CenterLat|FE|FN
13 Gnomonic             |Sphere|      |      |      |CentLon|CenterLat|FE|FN
14 Orthographic         |Sphere|      |      |      |CentLon|CenterLat|FE|FN
15 Gen. Vert. Near Per  |Sphere|      |Height|      |CentLon|CenterLat|FE|FN
16 Sinusoidal           |Sphere|      |      |      |CentMer|         |FE|FN
17 Equirectangular      |Sphere|      |      |      |CentMer|TrueScale|FE|FN
18 Miller Cylindrical   |Sphere|      |      |      |CentMer|         |FE|FN
19 Van der Grinten      |Sphere|      |      |      |CentMer|OriginLat|FE|FN
20 Hotin Oblique Merc A |SMajor|SMinor|Factor|      |       |OriginLat|FE|FN
   Hotin Oblique Merc B |SMajor|SMinor|Factor|AziAng|AzmthPt|OriginLat|FE|FN
21 Robinson             |Sphere|      |      |      |CentMer|         |FE|FN
22 Space Oblique Merc A |SMajor|SMinor|      |IncAng|AscLong|         |FE|FN
   Space Oblique Merc B |SMajor|SMinor|Satnum|Path  |       |         |FE|FN
23 Alaska Conformal     |SMajor|SMinor|      |      |       |         |FE|FN
24 Interrupted Goode    |Sphere|      |      |      |       |         |  |
25 Mollweide            |Sphere|      |      |      |CentMer|         |FE|FN
26 Interrupt Mollweide  |Sphere|      |      |      |       |         |  |
27 Hammer               |Sphere|      |      |      |CentMer|         |FE|FN
28 Wagner IV            |Sphere|      |      |      |CentMer|         |FE|FN
29 Wagner VII           |Sphere|      |      |      |CentMer|         |FE|FN
30 Oblated Equal Area   |Sphere|      |Shapem|Shapen|CentLon|CenterLat|FE|FN
----------------------------------------------------------------------------

      ----------------------------------------------------
                              |      Array Element       |
        Code & Projection Id  |---------------------------
                              |  8  |  9 |  10 | 11 | 12 |
      ----------------------------------------------------
       0 Geographic           |     |    |     |    |    |
       1 U T M                |     |    |     |    |    |
       2 State Plane          |     |    |     |    |    |
       3 Albers Equal Area    |     |    |     |    |    |
       4 Lambert Conformal C  |     |    |     |    |    |
       5 Mercator             |     |    |     |    |    |
       6 Polar Stereographic  |     |    |     |    |    |
       7 Polyconic            |     |    |     |    |    |
       8 Equid. Conic A       |zero |    |     |    |    |
         Equid. Conic B       |one  |    |     |    |    |
       9 Transverse Mercator  |     |    |     |    |    |
      10 Stereographic        |     |    |     |    |    |
      11 Lambert Azimuthal    |     |    |     |    |    |
      12 Azimuthal            |     |    |     |    |    |
      13 Gnomonic             |     |    |     |    |    |
      14 Orthographic         |     |    |     |    |    |
      15 Gen. Vert. Near Per  |     |    |     |    |    |
      16 Sinusoidal           |     |    |     |    |    |
      17 Equirectangular      |     |    |     |    |    |
      18 Miller Cylindrical   |     |    |     |    |    |
      19 Van der Grinten      |     |    |     |    |    |
      20 Hotin Oblique Merc A |Long1|Lat1|Long2|Lat2|zero|
         Hotin Oblique Merc B |     |    |     |    |one |
      21 Robinson             |     |    |     |    |    |
      22 Space Oblique Merc A |PSRev|LRat|PFlag|    |zero|
         Space Oblique Merc B |     |    |     |    |one |
      23 Alaska Conformal     |     |    |     |    |    |
      24 Interrupted Goode    |     |    |     |    |    |
      25 Mollweide            |     |    |     |    |    |
      26 Interrupt Mollweide  |     |    |     |    |    |
      27 Hammer               |     |    |     |    |    |
      28 Wagner IV            |     |    |     |    |    |
      29 Wagner VII           |     |    |     |    |    |
      30 Oblated Equal Area   |Angle|    |     |    |    |
      ----------------------------------------------------

  where

   Lon/Z     Longitude of any point in the UTM zone or zero.  If zero,
             a zone code must be specified.
   Lat/Z     Latitude of any point in the UTM zone or zero.  If zero, a
             zone code must be specified.
   SMajor    Semi-major axis of ellipsoid.  If zero, Clarke 1866 in meters
             is assumed.
   SMinor    Eccentricity squared of the ellipsoid if less than zero,
             if zero, a spherical form is assumed, or if greater than
             zero, the semi-minor axis of ellipsoid.
   Sphere    Radius of reference sphere.  If zero, 6370997 meters is used.
   STDPAR    Latitude of the standard parallel
   STDPR1    Latitude of the first standard parallel
   STDPR2    Latitude of the second standard parallel
   CentMer   Longitude of the central meridian
   OriginLat Latitude of the projection origin
   FE        False easting in the same units as the semi-major axis
   FN        False northing in the same units as the semi-major axis
   TrueScale Latitude of true scale
   LongPol   Longitude down below pole of map
   Factor    Scale factor at central meridian (Transverse Mercator) or
             center of projection (Hotine Oblique Mercator)
   CentLon   Longitude of center of projection
   CenterLat Latitude of center of projection
   Height    Height of perspective point
   Long1     Longitude of first point on center line (Hotine Oblique
             Mercator, format A)
   Long2     Longitude of second point on center line (Hotine Oblique
             Mercator, format A)
   Lat1      Latitude of first point on center line (Hotine Oblique
             Mercator, format A)
   Lat2      Latitude of second point on center line (Hotine Oblique
             Mercator, format A)
   AziAng    Azimuth angle east of north of center line (Hotine Oblique
             Mercator, format B)
   AzmthPt   Longitude of point on central meridian where azimuth occurs
             (Hotine Oblique Mercator, format B)
   IncAng    Inclination of orbit at ascending node, counter-clockwise
             from equator (SOM, format A)
   AscLong   Longitude of ascending orbit at equator (SOM, format A)
   PSRev     Period of satellite revolution in minutes (SOM, format A)
   LRat      Landsat ratio to compensate for confusion at northern end
             of orbit (SOM, format A -- use 0.5201613)
   PFlag     End of path flag for Landsat:  0 = start of path,
             1 = end of path (SOM, format A)
   Satnum    Landsat Satellite Number (SOM, format B)
   Path      Landsat Path Number (Use WRS-1 for Landsat 1, 2 and 3 and
             WRS-2 for Landsat 4, 5 and 6.)  (SOM, format B)
   Shapem    Oblated Equal Area oval shape parameter m
   Shapen    Oblated Equal Area oval shape parameter n
   Angle     Oblated Equal Area oval rotation angle

Array elements 13 and 14 are set to zero. All array elements with blank
fields are set to zero too.
\endverbatim

@param iDatum Input spheroid.<p>

If the datum code is negative, the first two values in the parameter array
(param) are used to define the values as follows:

<ul>

<li> If padfPrjParams[0] is a non-zero value and padfPrjParams[1] is
greater than one, the semimajor axis is set to padfPrjParams[0] and
the semiminor axis is set to padfPrjParams[1].

<li> If padfPrjParams[0] is nonzero and padfPrjParams[1] is greater than
zero but less than or equal to one, the semimajor axis is set to
padfPrjParams[0] and the semiminor axis is computed from the eccentricity
squared value padfPrjParams[1]:<p>

semiminor = sqrt(1.0 - ES)semimajor<p>

where<p>

ES = eccentricity squared

<li> If padfPrjParams[0] is nonzero and padfPrjParams[1] is equal to zero,
the semimajor axis and semiminor axis are set to padfPrjParams[0].

<li> If padfPrjParams[0] equals zero and padfPrjParams[1] is greater than
zero, the default Clarke 1866 is used to assign values to the semimajor
axis and semiminor axis.

<li> If padfPrjParams[0] and padfPrjParams[1] equals zero, the semimajor
axis is set to 6370997.0 and the semiminor axis is set to zero.

</ul>

If a datum code is zero or greater, the semimajor and semiminor axis are
defined by the datum code as found in the following table:

Supported Datums are:
<ul>
<li>0: Clarke 1866 (default)
<li>1: Clarke 1880
<li>2: Bessel
<li>3: International 1967
<li>4: International 1909
<li>5: WGS 72
<li>6: Everest
<li>7: WGS 66
<li>8: GRS 1980/WGS 84
<li>9: Airy
<li>10: Modified Everest
<li>11: Modified Airy
<li>12: WGS 84
<li>13: Southeast Asia
<li>14: Australian National
<li>15: Krassovsky
<li>16: Hough
<li>17: Mercury 1960
<li>18: Modified Mercury 1968
<li>19: Sphere of Radius 6370997 meters
</ul>

@param nUSGSAngleFormat one of USGS_ANGLE_DECIMALDEGREES,
   USGS_ANGLE_PACKEDDMS, or USGS_ANGLE_RADIANS (default is
   USGS_ANGLE_PACKEDDMS).

@return OGRERR_NONE on success or an error code in case of failure.
 */

OGRErr OGRSpatialReference::importFromUSGS(long iProjSys, long iZone,
                                           double *padfPrjParams, long iDatum,
                                           int nUSGSAngleFormat)

{
    if (!padfPrjParams)
        return OGRERR_CORRUPT_DATA;

    double (*pfnUnpackAnglesFn)(double) = nullptr;

    if (nUSGSAngleFormat == USGS_ANGLE_DECIMALDEGREES)
        pfnUnpackAnglesFn = OGRSpatialReferenceUSGSUnpackNoOp;
    else if (nUSGSAngleFormat == USGS_ANGLE_RADIANS)
        pfnUnpackAnglesFn = OGRSpatialReferenceUSGSUnpackRadian;
    else
        pfnUnpackAnglesFn = CPLPackedDMSToDec;

    /* -------------------------------------------------------------------- */
    /*      Operate on the basis of the projection code.                    */
    /* -------------------------------------------------------------------- */
    switch (iProjSys)
    {
        case GEO:
            break;

        case UTM:
        {
            int bNorth = TRUE;

            if (!iZone)
            {
                if (padfPrjParams[2] != 0.0)
                {
                    iZone = static_cast<long>(padfPrjParams[2]);
                }
                else if (padfPrjParams[0] != 0.0 && padfPrjParams[1] != 0.0)
                {
                    const double dfUnpackedAngle =
                        pfnUnpackAnglesFn(padfPrjParams[0]);
                    iZone = static_cast<long>(
                        ((dfUnpackedAngle + 180.0) / 6.0) + 1.0);
                    if (dfUnpackedAngle < 0)
                        bNorth = FALSE;
                }
            }

            if (iZone < -60 || iZone > 60)
                return OGRERR_CORRUPT_DATA;

            if (iZone < 0)
            {
                iZone = -iZone;
                bNorth = FALSE;
            }
            SetUTM(static_cast<int>(iZone), bNorth);
        }
        break;

        case SPCS:
        {
            int bNAD83 = TRUE;

            if (iDatum == 0)
                bNAD83 = FALSE;
            else if (iDatum != 8)
                CPLError(CE_Warning, CPLE_AppDefined,
                         "Wrong datum for State Plane projection %d. "
                         "Should be 0 or 8.",
                         static_cast<int>(iDatum));

            SetStatePlane(static_cast<int>(iZone), bNAD83);
        }
        break;

        case ALBERS:
            SetACEA(pfnUnpackAnglesFn(padfPrjParams[2]),
                    pfnUnpackAnglesFn(padfPrjParams[3]),
                    pfnUnpackAnglesFn(padfPrjParams[5]),
                    pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                    padfPrjParams[7]);
            break;

        case LAMCC:
            SetLCC(pfnUnpackAnglesFn(padfPrjParams[2]),
                   pfnUnpackAnglesFn(padfPrjParams[3]),
                   pfnUnpackAnglesFn(padfPrjParams[5]),
                   pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                   padfPrjParams[7]);
            break;

        case MERCAT:
            SetMercator(pfnUnpackAnglesFn(padfPrjParams[5]),
                        pfnUnpackAnglesFn(padfPrjParams[4]), 1.0,
                        padfPrjParams[6], padfPrjParams[7]);
            break;

        case PS:
            SetPS(pfnUnpackAnglesFn(padfPrjParams[5]),
                  pfnUnpackAnglesFn(padfPrjParams[4]), 1.0, padfPrjParams[6],
                  padfPrjParams[7]);

            break;

        case POLYC:
            SetPolyconic(pfnUnpackAnglesFn(padfPrjParams[5]),
                         pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                         padfPrjParams[7]);
            break;

        case EQUIDC:
            if (padfPrjParams[8] != 0.0)
            {
                SetEC(pfnUnpackAnglesFn(padfPrjParams[2]),
                      pfnUnpackAnglesFn(padfPrjParams[3]),
                      pfnUnpackAnglesFn(padfPrjParams[5]),
                      pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                      padfPrjParams[7]);
            }
            else
            {
                SetEC(pfnUnpackAnglesFn(padfPrjParams[2]),
                      pfnUnpackAnglesFn(padfPrjParams[2]),
                      pfnUnpackAnglesFn(padfPrjParams[5]),
                      pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                      padfPrjParams[7]);
            }
            break;

        case TM:
            SetTM(pfnUnpackAnglesFn(padfPrjParams[5]),
                  pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[2],
                  padfPrjParams[6], padfPrjParams[7]);
            break;

        case STEREO:
            SetStereographic(pfnUnpackAnglesFn(padfPrjParams[5]),
                             pfnUnpackAnglesFn(padfPrjParams[4]), 1.0,
                             padfPrjParams[6], padfPrjParams[7]);
            break;

        case LAMAZ:
            SetLAEA(pfnUnpackAnglesFn(padfPrjParams[5]),
                    pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                    padfPrjParams[7]);
            break;

        case AZMEQD:
            SetAE(pfnUnpackAnglesFn(padfPrjParams[5]),
                  pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                  padfPrjParams[7]);
            break;

        case GNOMON:
            SetGnomonic(pfnUnpackAnglesFn(padfPrjParams[5]),
                        pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                        padfPrjParams[7]);
            break;

        case ORTHO:
            SetOrthographic(pfnUnpackAnglesFn(padfPrjParams[5]),
                            pfnUnpackAnglesFn(padfPrjParams[4]),
                            padfPrjParams[6], padfPrjParams[7]);
            break;

            // FIXME: GVNSP --- General Vertical Near-Side Perspective skipped.

        case SNSOID:
            SetSinusoidal(pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                          padfPrjParams[7]);
            break;

        case EQRECT:
            SetEquirectangular2(0.0, pfnUnpackAnglesFn(padfPrjParams[4]),
                                pfnUnpackAnglesFn(padfPrjParams[5]),
                                padfPrjParams[6], padfPrjParams[7]);
            break;

        case MILLER:
            SetMC(pfnUnpackAnglesFn(padfPrjParams[5]),
                  pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                  padfPrjParams[7]);
            break;

        case VGRINT:
            SetVDG(pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                   padfPrjParams[7]);
            break;

        case HOM:
            if (padfPrjParams[12] != 0.0)
            {
                SetHOM(pfnUnpackAnglesFn(padfPrjParams[5]),
                       pfnUnpackAnglesFn(padfPrjParams[4]),
                       pfnUnpackAnglesFn(padfPrjParams[3]), 0.0,
                       padfPrjParams[2], padfPrjParams[6], padfPrjParams[7]);
            }
            else
            {
                SetHOM2PNO(pfnUnpackAnglesFn(padfPrjParams[5]),
                           pfnUnpackAnglesFn(padfPrjParams[9]),
                           pfnUnpackAnglesFn(padfPrjParams[8]),
                           pfnUnpackAnglesFn(padfPrjParams[11]),
                           pfnUnpackAnglesFn(padfPrjParams[10]),
                           padfPrjParams[2], padfPrjParams[6],
                           padfPrjParams[7]);
            }
            break;

        case ROBIN:
            SetRobinson(pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                        padfPrjParams[7]);
            break;

            // FIXME: SOM --- Space Oblique Mercator skipped.
            // FIXME: ALASKA --- Alaska Conformal skipped.
            // FIXME: GOODE --- Interrupted Goode skipped.

        case MOLL:
            SetMollweide(pfnUnpackAnglesFn(padfPrjParams[4]), padfPrjParams[6],
                         padfPrjParams[7]);
            break;

            // FIXME: IMOLL --- Interrupted Mollweide skipped.
            // FIXME: HAMMER --- Hammer skipped.

        case WAGIV:
            SetWagner(4, 0.0, padfPrjParams[6], padfPrjParams[7]);
            break;

        case WAGVII:
            SetWagner(7, 0.0, padfPrjParams[6], padfPrjParams[7]);
            break;

            // FIXME: OBEQA --- Oblated Equal Area skipped.
            // FIXME: ISINUS1 --- Integerized Sinusoidal Grid (the same as 99).
            // FIXME: CEA --- Cylindrical Equal Area skipped (Grid corners set
            // in meters for EASE grid).
            // FIXME: BCEA --- Cylindrical Equal Area skipped (Grid corners set
            // in DMS degs for EASE grid).
            // FIXME: ISINUS --- Integrized Sinusoidal skipped.

        default:
            CPLDebug("OSR_USGS", "Unsupported projection: %ld", iProjSys);
            SetLocalCS(
                CPLString().Printf("GCTP projection number %ld", iProjSys));
            break;
    }

    /* -------------------------------------------------------------------- */
    /*      Try to translate the datum/spheroid.                            */
    /* -------------------------------------------------------------------- */

    if (!IsLocal())
    {
        char *pszName = nullptr;
        double dfSemiMajor = 0.0;
        double dfInvFlattening = 0.0;

        if (iDatum < 0)  // Use specified ellipsoid parameters.
        {
            if (padfPrjParams[0] > 0.0)
            {
                if (padfPrjParams[1] > 1.0)
                {
                    dfInvFlattening = OSRCalcInvFlattening(padfPrjParams[0],
                                                           padfPrjParams[1]);
                }
                else if (padfPrjParams[1] > 0.0)
                {
                    dfInvFlattening =
                        1.0 / (1.0 - sqrt(1.0 - padfPrjParams[1]));
                }
                else
                {
                    dfInvFlattening = 0.0;
                }

                SetGeogCS("Unknown datum based upon the custom spheroid",
                          "Not specified (based on custom spheroid)",
                          "Custom spheroid", padfPrjParams[0], dfInvFlattening,
                          nullptr, 0, nullptr, 0);
            }
            else if (padfPrjParams[1] > 0.0)  // Clarke 1866.
            {
                if (OSRGetEllipsoidInfo(7008, &pszName, &dfSemiMajor,
                                        &dfInvFlattening) == OGRERR_NONE)
                {
                    SetGeogCS(
                        CPLString().Printf(
                            "Unknown datum based upon the %s ellipsoid",
                            pszName),
                        CPLString().Printf(
                            "Not specified (based on %s spheroid)", pszName),
                        pszName, dfSemiMajor, dfInvFlattening, nullptr, 0.0,
                        nullptr, 0.0);
                    SetAuthority("SPHEROID", "EPSG", 7008);
                }
            }
            else  // Sphere, rad 6370997 m
            {
                if (OSRGetEllipsoidInfo(7047, &pszName, &dfSemiMajor,
                                        &dfInvFlattening) == OGRERR_NONE)
                {
                    SetGeogCS(
                        CPLString().Printf(
                            "Unknown datum based upon the %s ellipsoid",
                            pszName),
                        CPLString().Printf(
                            "Not specified (based on %s spheroid)", pszName),
                        pszName, dfSemiMajor, dfInvFlattening, nullptr, 0.0,
                        nullptr, 0.0);
                    SetAuthority("SPHEROID", "EPSG", 7047);
                }
            }
        }
        else if (iDatum < NUMBER_OF_ELLIPSOIDS && aoEllips[iDatum])
        {
            if (OSRGetEllipsoidInfo(aoEllips[iDatum], &pszName, &dfSemiMajor,
                                    &dfInvFlattening) == OGRERR_NONE)
            {
                SetGeogCS(
                    CPLString().Printf(
                        "Unknown datum based upon the %s ellipsoid", pszName),
                    CPLString().Printf("Not specified (based on %s spheroid)",
                                       pszName),
                    pszName, dfSemiMajor, dfInvFlattening, nullptr, 0.0,
                    nullptr, 0.0);
                SetAuthority("SPHEROID", "EPSG", aoEllips[iDatum]);
            }
            else
            {
                CPLError(CE_Warning, CPLE_AppDefined,
                         "Failed to lookup datum code %d. "
                         "Falling back to use WGS84.",
                         static_cast<int>(iDatum));
                SetWellKnownGeogCS("WGS84");
            }
        }
        else
        {
            CPLError(CE_Warning, CPLE_AppDefined,
                     "Wrong datum code %d. Supported datums 0--%d only.  "
                     "Setting WGS84 as a fallback.",
                     static_cast<int>(iDatum), NUMBER_OF_ELLIPSOIDS);
            SetWellKnownGeogCS("WGS84");
        }

        CPLFree(pszName);
    }

    /* -------------------------------------------------------------------- */
    /*      Grid units translation                                          */
    /* -------------------------------------------------------------------- */
    if (IsLocal() || IsProjected())
        SetLinearUnits(SRS_UL_METER, 1.0);

    return OGRERR_NONE;
}

/************************************************************************/
/*                          OSRExportToUSGS()                           */
/************************************************************************/
/**
 * \brief Export coordinate system in USGS GCTP projection definition.
 *
 * This function is the same as OGRSpatialReference::exportToUSGS().
 */

OGRErr OSRExportToUSGS(OGRSpatialReferenceH hSRS, long *piProjSys, long *piZone,
                       double **ppadfPrjParams, long *piDatum)

{
    VALIDATE_POINTER1(hSRS, "OSRExportToUSGS", OGRERR_FAILURE);

    *ppadfPrjParams = nullptr;

    return OGRSpatialReference::FromHandle(hSRS)->exportToUSGS(
        piProjSys, piZone, ppadfPrjParams, piDatum);
}

/************************************************************************/
/*                           exportToUSGS()                             */
/************************************************************************/

/**
 * \brief Export coordinate system in USGS GCTP projection definition.
 *
 * This method is the equivalent of the C function OSRExportToUSGS().
 *
 * @param piProjSys Pointer to variable, where the projection system code will
 * be returned.
 *
 * @param piZone Pointer to variable, where the zone for UTM and State Plane
 * projection systems will be returned.
 *
 * @param ppadfPrjParams Pointer to which dynamically allocated array of
 * 15 projection parameters will be assigned. See importFromUSGS() for
 * the list of parameters. Caller responsible to free this array.
 *
 * @param piDatum Pointer to variable, where the datum code will
 * be returned.
 *
 * @return OGRERR_NONE on success or an error code on failure.
 */

OGRErr OGRSpatialReference::exportToUSGS(long *piProjSys, long *piZone,
                                         double **ppadfPrjParams,
                                         long *piDatum) const

{
    const char *pszProjection = GetAttrValue("PROJECTION");

    /* -------------------------------------------------------------------- */
    /*      Fill all projection parameters with zero.                       */
    /* -------------------------------------------------------------------- */
    *ppadfPrjParams = static_cast<double *>(CPLMalloc(15 * sizeof(double)));
    for (int i = 0; i < 15; i++)
        (*ppadfPrjParams)[i] = 0.0;

    *piZone = 0L;

    /* ==================================================================== */
    /*      Handle the projection definition.                               */
    /* ==================================================================== */
    if (IsLocal())
        *piProjSys = GEO;

    else if (pszProjection == nullptr)
    {
#ifdef DEBUG
        CPLDebug("OSR_USGS",
                 "Empty projection definition, considered as Geographic");
#endif
        *piProjSys = GEO;
    }

    else if (EQUAL(pszProjection, SRS_PT_ALBERS_CONIC_EQUAL_AREA))
    {
        *piProjSys = ALBERS;
        (*ppadfPrjParams)[2] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_STANDARD_PARALLEL_1, 0.0));
        (*ppadfPrjParams)[3] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_STANDARD_PARALLEL_2, 0.0));
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_LAMBERT_CONFORMAL_CONIC_2SP))
    {
        *piProjSys = LAMCC;
        (*ppadfPrjParams)[2] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_STANDARD_PARALLEL_1, 0.0));
        (*ppadfPrjParams)[3] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_STANDARD_PARALLEL_2, 0.0));
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_MERCATOR_1SP))
    {
        *piProjSys = MERCAT;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_POLAR_STEREOGRAPHIC))
    {
        *piProjSys = PS;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_POLYCONIC))
    {
        *piProjSys = POLYC;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_EQUIDISTANT_CONIC))
    {
        *piProjSys = EQUIDC;
        (*ppadfPrjParams)[2] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_STANDARD_PARALLEL_1, 0.0));
        (*ppadfPrjParams)[3] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_STANDARD_PARALLEL_2, 0.0));
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
        (*ppadfPrjParams)[8] = 1.0;
    }

    else if (EQUAL(pszProjection, SRS_PT_TRANSVERSE_MERCATOR))
    {
        int bNorth;

        *piZone = GetUTMZone(&bNorth);

        if (*piZone != 0)
        {
            *piProjSys = UTM;
            if (!bNorth)
                *piZone = -*piZone;
        }
        else
        {
            *piProjSys = TM;
            (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
            (*ppadfPrjParams)[4] = CPLDecToPackedDMS(
                GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
            (*ppadfPrjParams)[5] = CPLDecToPackedDMS(
                GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
            (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
            (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
        }
    }

    else if (EQUAL(pszProjection, SRS_PT_STEREOGRAPHIC))
    {
        *piProjSys = STEREO;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_LAMBERT_AZIMUTHAL_EQUAL_AREA))
    {
        *piProjSys = LAMAZ;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_AZIMUTHAL_EQUIDISTANT))
    {
        *piProjSys = AZMEQD;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LONGITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_GNOMONIC))
    {
        *piProjSys = GNOMON;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_ORTHOGRAPHIC))
    {
        *piProjSys = ORTHO;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_SINUSOIDAL))
    {
        *piProjSys = SNSOID;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LONGITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_EQUIRECTANGULAR))
    {
        *piProjSys = EQRECT;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_STANDARD_PARALLEL_1, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_MILLER_CYLINDRICAL))
    {
        *piProjSys = MILLER;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LONGITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_VANDERGRINTEN))
    {
        *piProjSys = VGRINT;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LONGITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_HOTINE_OBLIQUE_MERCATOR))
    {
        *piProjSys = HOM;
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
        (*ppadfPrjParams)[3] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_AZIMUTH, 0.0));
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LONGITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
        (*ppadfPrjParams)[12] = 1.0;
    }

    else if (EQUAL(pszProjection,
                   SRS_PT_HOTINE_OBLIQUE_MERCATOR_TWO_POINT_NATURAL_ORIGIN))
    {
        *piProjSys = HOM;
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
        (*ppadfPrjParams)[5] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
        (*ppadfPrjParams)[8] = CPLDecToPackedDMS(
            GetNormProjParm(SRS_PP_LONGITUDE_OF_POINT_1, 0.0));
        (*ppadfPrjParams)[9] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_POINT_1, 0.0));
        (*ppadfPrjParams)[10] = CPLDecToPackedDMS(
            GetNormProjParm(SRS_PP_LONGITUDE_OF_POINT_2, 0.0));
        (*ppadfPrjParams)[11] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LATITUDE_OF_POINT_2, 0.0));
        (*ppadfPrjParams)[12] = 0.0;
    }

    else if (EQUAL(pszProjection, SRS_PT_ROBINSON))
    {
        *piProjSys = ROBIN;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_LONGITUDE_OF_CENTER, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_MOLLWEIDE))
    {
        *piProjSys = MOLL;
        (*ppadfPrjParams)[4] =
            CPLDecToPackedDMS(GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0));
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_WAGNER_IV))
    {
        *piProjSys = WAGIV;
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }

    else if (EQUAL(pszProjection, SRS_PT_WAGNER_VII))
    {
        *piProjSys = WAGVII;
        (*ppadfPrjParams)[6] = GetNormProjParm(SRS_PP_FALSE_EASTING, 0.0);
        (*ppadfPrjParams)[7] = GetNormProjParm(SRS_PP_FALSE_NORTHING, 0.0);
    }
    // Projection unsupported by GCTP.
    else
    {
        CPLDebug("OSR_USGS",
                 "Projection \"%s\" unsupported by USGS GCTP. "
                 "Geographic system will be used.",
                 pszProjection);
        *piProjSys = GEO;
    }

    /* -------------------------------------------------------------------- */
    /*      Translate the datum.                                            */
    /* -------------------------------------------------------------------- */
    const char *pszDatum = GetAttrValue("DATUM");

    if (pszDatum)
    {
        if (EQUAL(pszDatum, SRS_DN_NAD27))
        {
            *piDatum = CLARKE1866;
        }
        else if (EQUAL(pszDatum, SRS_DN_NAD83))
        {
            *piDatum = GRS1980;
        }
        else if (EQUAL(pszDatum, SRS_DN_WGS84))
        {
            *piDatum = WGS84;
        }
        // If not found well known datum, translate ellipsoid.
        else
        {
            const double dfSemiMajor = GetSemiMajor();
            const double dfInvFlattening = GetInvFlattening();

#ifdef DEBUG
            CPLDebug("OSR_USGS",
                     "Datum \"%s\" unsupported by USGS GCTP. "
                     "Try to translate ellipsoid definition.",
                     pszDatum);
#endif

            int i = 0;  // Used after for.
            for (; i < NUMBER_OF_ELLIPSOIDS; i++)
            {
                double dfSM = 0.0;
                double dfIF = 0.0;

                if (OSRGetEllipsoidInfo(aoEllips[i], nullptr, &dfSM, &dfIF) ==
                        OGRERR_NONE &&
                    CPLIsEqual(dfSemiMajor, dfSM) &&
                    CPLIsEqual(dfInvFlattening, dfIF))
                {
                    *piDatum = i;
                    break;
                }
            }

            if (i == NUMBER_OF_ELLIPSOIDS)  // Didn't found matches; set
            {                               // custom ellipsoid parameters.
#ifdef DEBUG
                CPLDebug("OSR_USGS",
                         "Ellipsoid \"%s\" unsupported by USGS GCTP. "
                         "Custom ellipsoid definition will be used.",
                         pszDatum);
#endif
                *piDatum = -1;
                (*ppadfPrjParams)[0] = dfSemiMajor;
                if (std::abs(dfInvFlattening) < 0.000000000001)
                {
                    (*ppadfPrjParams)[1] = dfSemiMajor;
                }
                else
                {
                    (*ppadfPrjParams)[1] =
                        dfSemiMajor * (1.0 - 1.0 / dfInvFlattening);
                }
            }
        }
    }
    else
    {
        *piDatum = -1;
    }

    return OGRERR_NONE;
}
