/******************************************************************************
 *
 * Project:  OpenGIS Simple Features Reference Implementation
 * Purpose:  OGRSpatialReference translation to/from PCI georeferencing
 *           information.
 * Author:   Andrey Kiselev, dron@ak4719.spb.edu
 *
 ******************************************************************************
 * Copyright (c) 2003, Andrey Kiselev <dron@ak4719.spb.edu>
 * Copyright (c) 2009-2011, Even Rouault <even dot rouault at spatialys.com>
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/

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

#include <cctype>
#include <cstdio>
#include <cstdlib>
#include <cstring>

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

// PCI uses a 16-character string for coordinate system and datum/ellipsoid.
constexpr int knProjSize = 16;

struct PCIDatums
{
    const char *pszPCIDatum;
    int nEPSGCode;
};

static const PCIDatums asDatums[] = {
    {"D-01", 4267},  // NAD27 (USA, NADCON)
    {"D-03", 4267},  // NAD27 (Canada, NTv1)
    {"D-02", 4269},  // NAD83 (USA, NADCON)
    {"D-04", 4269},  // NAD83 (Canada, NTv1)
    {"D000", 4326},  // WGS 1984
    {"D001", 4322},  // WGS 1972
    {"D008", 4296},  // Sudan
    {"D013", 4601},  // Antigua Island Astro 1943
    {"D029", 4202},  // Australian Geodetic 1966
    {"D030", 4203},  // Australian Geodetic 1984
    {"D033", 4216},  // Bermuda 1957
    {"D034", 4165},  // Bissau
    {"D036", 4219},  // Bukit Rimpah
    {"D038", 4221},  // Campo Inchauspe
    {"D040", 4222},  // Cape
    {"D042", 4223},  // Carthage
    {"D044", 4224},  // Chua Astro
    {"D045", 4225},  // Corrego Alegre
    {"D046", 4155},  // Dabola (Guinea)
    {"D066", 4272},  // Geodetic Datum 1949 (New Zealand)
    {"D071", 4255},  // Herat North (Afghanistan)
    {"D077", 4239},  // Indian 1954 (Thailand, Vietnam)
    {"D078", 4240},  // Indian 1975 (Thailand)
    {"D083", 4244},  // Kandawala (Sri Lanka)
    {"D085", 4245},  // Kertau 1948 (West Malaysia & Singapore)
    {"D088", 4250},  // Leigon (Ghana)
    {"D089", 4251},  // Liberia 1964 (Liberia)
    {"D092", 4256},  // Mahe 1971 (Mahe Island)
    {"D093", 4262},  // Massawa (Ethiopia (Eritrea))
    {"D094", 4261},  // Merchich (Morocco)
    {"D098",
     4604},  // Montserrat Island Astro 1958 (Montserrat (Leeward Islands))
    {"D110", 4267},  // NAD27 / Alaska
    {"D139", 4282},  // Pointe Noire 1948 (Congo)
    {"D140", 4615},  // Porto Santo 1936 (Porto Santo, Madeira Islands)
    {"D151", 4139},  // Puerto Rico (Puerto Rico, Virgin Islands)
    {"D153", 4287},  // Qornoq (Greenland (South))
    {"D158", 4292},  // Sapper Hill 1943 (East Falkland Island)
    {"D159", 4293},  // Schwarzeck (Namibia)
    {"D160", 4616},  // Selvagem Grande 1938 (Salvage Islands)
    {"D176", 4297},  // Tananarive Observatory 1925 (Madagascar)
    {"D177", 4298},  // Timbalai 1948 (Brunei, East Malaysia (Sabah, Sarawak))
    {"D187", 4309},  // Yacare (Uruguay)
    {"D188", 4311},  // Zanderij (Suriname)
    {"D401", 4124},  // RT90 (Sweden)
    {"D501", 4312},  // MGI (Hermannskogel, Austria)
    {nullptr, 0}};

static const PCIDatums asEllips[] = {
    {"E000", 7008},  // Clarke, 1866 (NAD1927)
    {"E001", 7034},  // Clarke, 1880
    {"E002", 7004},  // Bessel, 1841
    {"E004", 7022},  // International, 1924 (Hayford, 1909)
    {"E005", 7043},  // WGS, 1972
    {"E006", 7042},  // Everest, 1830
    {"E008", 7019},  // GRS, 1980 (NAD1983)
    {"E009", 7001},  // Airy, 1830
    {"E010", 7018},  // Modified Everest
    {"E011", 7002},  // Modified Airy
    {"E012", 7030},  // WGS, 1984 (GPS)
    {"E014", 7003},  // Australian National, 1965
    {"E015", 7024},  // Krassovsky, 1940
    {"E016", 7053},  // Hough
    {"E019", 7052},  // normal sphere
    {"E333", 7046},  // Bessel 1841 (Japan By Law)
    {"E900", 7006},  // Bessel, 1841 (Namibia)
    {"E901", 7044},  // Everest, 1956
    {"E902", 7056},  // Everest, 1969
    {"E903", 7016},  // Everest (Sabah & Sarawak)
    {"E904", 7020},  // Helmert, 1906
    {"E907", 7036},  // South American, 1969
    {"E910", 7041},  // ATS77
    {nullptr, 0}};

/************************************************************************/
/*                         OSRImportFromPCI()                           */
/************************************************************************/

/**
 * \brief Import coordinate system from PCI projection definition.
 *
 * This function is the same as OGRSpatialReference::importFromPCI().
 */

OGRErr OSRImportFromPCI(OGRSpatialReferenceH hSRS, const char *pszProj,
                        const char *pszUnits, double *padfPrjParams)

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

    return OGRSpatialReference::FromHandle(hSRS)->importFromPCI(
        pszProj, pszUnits, padfPrjParams);
}

/************************************************************************/
/*                          importFromPCI()                             */
/************************************************************************/

/**
 * \brief Import coordinate system from PCI projection definition.
 *
 * PCI software uses 16-character string to specify coordinate system
 * and datum/ellipsoid. You should supply at least this string to the
 * importFromPCI() function.
 *
 * This function is the equivalent of the C function OSRImportFromPCI().
 *
 * @param pszProj NULL terminated string containing the definition. Looks
 * like "pppppppppppp Ennn" or "pppppppppppp Dnnn", where "pppppppppppp" is
 * a projection code, "Ennn" is an ellipsoid code, "Dnnn" a datum code.
 *
 * @param pszUnits Grid units code ("DEGREE" or "METRE"). If NULL "METRE" will
 * be used.
 *
 * @param padfPrjParams Array of 17 coordinate system parameters:
 *
 * [0]  Spheroid semi major axis
 * [1]  Spheroid semi minor axis
 * [2]  Reference Longitude
 * [3]  Reference Latitude
 * [4]  First Standard Parallel
 * [5]  Second Standard Parallel
 * [6]  False Easting
 * [7]  False Northing
 * [8]  Scale Factor
 * [9]  Height above sphere surface
 * [10] Longitude of 1st point on center line
 * [11] Latitude of 1st point on center line
 * [12] Longitude of 2nd point on center line
 * [13] Latitude of 2nd point on center line
 * [14] Azimuth east of north for center line
 * [15] Landsat satellite number
 * [16] Landsat path number
 *
 * Particular projection uses different parameters, unused ones may be set to
 * zero. If NULL is supplied instead of an array pointer, default values will be
 * used (i.e., zeroes).
 *
 * @return OGRERR_NONE on success or an error code in case of failure.
 */

OGRErr OGRSpatialReference::importFromPCI(const char *pszProj,
                                          const char *pszUnits,
                                          const double *padfPrjParams)

{
    Clear();

    if (pszProj == nullptr ||
        CPLStrnlen(pszProj, knProjSize) < static_cast<size_t>(knProjSize))
    {
        return OGRERR_CORRUPT_DATA;
    }

    CPLDebug("OSR_PCI", "Trying to import projection \"%s\"", pszProj);

    /* -------------------------------------------------------------------- */
    /*      Use safe defaults if projection parameters are not supplied.    */
    /* -------------------------------------------------------------------- */
    static const double adfZeroedPrjParams[17] = {0};
    if (padfPrjParams == nullptr)
    {
        padfPrjParams = adfZeroedPrjParams;
    }

    /* -------------------------------------------------------------------- */
    /*      Extract and "normalize" the earthmodel to look like E001,       */
    /*      D-02 or D109.                                                   */
    /* -------------------------------------------------------------------- */
    char szEarthModel[5] = {};

    strcpy(szEarthModel, "");
    const char *pszEM = pszProj + strlen(pszProj) - 1;
    while (pszEM != pszProj)
    {
        if (*pszEM == 'e' || *pszEM == 'E' || *pszEM == 'd' || *pszEM == 'D')
        {
            int nCode = atoi(pszEM + 1);

            if (nCode >= -99 && nCode <= 999)
                snprintf(szEarthModel, sizeof(szEarthModel), "%c%03d",
                         CPLToupper(static_cast<unsigned char>(*pszEM)), nCode);

            break;
        }

        pszEM--;
    }

    const bool bIsNAD27 = EQUAL(pszEM, "E000") || EQUAL(pszEM, "D-01") ||
                          EQUAL(pszEM, "D-03") || EQUAL(pszEM, "D-07") ||
                          EQUAL(pszEM, "D-09") || EQUAL(pszEM, "D-11") ||
                          EQUAL(pszEM, "D-13") || EQUAL(pszEM, "D-17");

    /* -------------------------------------------------------------------- */
    /*      Operate on the basis of the projection name.                    */
    /* -------------------------------------------------------------------- */
    if (STARTS_WITH_CI(pszProj, "LONG/LAT"))
    {
        // TODO(schwehr): A NOP is okay?
    }
    else if (STARTS_WITH_CI(pszProj, "METER") ||
             STARTS_WITH_CI(pszProj, "METRE"))
    {
        SetLocalCS("METER");
        SetLinearUnits("METER", 1.0);
    }
    else if (STARTS_WITH_CI(pszProj, "FEET") || STARTS_WITH_CI(pszProj, "FOOT"))
    {
        SetLocalCS("FEET");
        SetLinearUnits("FEET", CPLAtof(SRS_UL_FOOT_CONV));
    }
    else if (STARTS_WITH_CI(pszProj, "ACEA"))
    {
        SetACEA(padfPrjParams[4], padfPrjParams[5], padfPrjParams[3],
                padfPrjParams[2], padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "AE"))
    {
        SetAE(padfPrjParams[3], padfPrjParams[2], padfPrjParams[6],
              padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "CASS "))
    {
        SetCS(padfPrjParams[3], padfPrjParams[2], padfPrjParams[6],
              padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "EC"))
    {
        SetEC(padfPrjParams[4], padfPrjParams[5], padfPrjParams[3],
              padfPrjParams[2], padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "ER"))
    {
        // PCI and GCTP don't support natural origin lat.
        SetEquirectangular2(0.0, padfPrjParams[2], padfPrjParams[3],
                            padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "GNO"))
    {
        SetGnomonic(padfPrjParams[3], padfPrjParams[2], padfPrjParams[6],
                    padfPrjParams[7]);
    }
    // FIXME: GVNP --- General Vertical Near- Side Perspective skipped.
    // FIXME: GOOD -- Our Goode's is not the interrupted version from PCI.
    else if (STARTS_WITH_CI(pszProj, "LAEA"))
    {
        SetLAEA(padfPrjParams[3], padfPrjParams[2], padfPrjParams[6],
                padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "LCC "))
    {
        SetLCC(padfPrjParams[4], padfPrjParams[5], padfPrjParams[3],
               padfPrjParams[2], padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "LCC_1SP "))
    {
        SetLCC1SP(padfPrjParams[3], padfPrjParams[2], padfPrjParams[8],
                  padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "MC"))
    {
        SetMC(padfPrjParams[3], padfPrjParams[2], padfPrjParams[6],
              padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "MER"))
    {
        if (EQUAL(pszEM, "D894") && padfPrjParams[3] == 0 &&
            padfPrjParams[2] == 0 && padfPrjParams[8] == 1.0 &&
            padfPrjParams[6] == 0 && padfPrjParams[7] == 0)
        {
            // Special case for Web Mercator
            return importFromEPSG(3857);
        }
        SetMercator(padfPrjParams[3], padfPrjParams[2],
                    (padfPrjParams[8] != 0.0) ? padfPrjParams[8] : 1.0,
                    padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "OG"))
    {
        SetOrthographic(padfPrjParams[3], padfPrjParams[2], padfPrjParams[6],
                        padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "OM "))
    {
        if (padfPrjParams[10] == 0.0 && padfPrjParams[11] == 0.0 &&
            padfPrjParams[12] == 0.0 && padfPrjParams[13] == 0.0)
        {
            SetHOM(padfPrjParams[3], padfPrjParams[2], padfPrjParams[14],
                   padfPrjParams[14],  // Use azimuth for grid angle.
                   padfPrjParams[8], padfPrjParams[6], padfPrjParams[7]);
        }
        else
        {
            SetHOM2PNO(padfPrjParams[3], padfPrjParams[11], padfPrjParams[10],
                       padfPrjParams[13], padfPrjParams[12], padfPrjParams[8],
                       padfPrjParams[6], padfPrjParams[7]);
        }
    }
    else if (STARTS_WITH_CI(pszProj, "PC"))
    {
        SetPolyconic(padfPrjParams[3], padfPrjParams[2], padfPrjParams[6],
                     padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "PS"))
    {
        SetPS(padfPrjParams[3], padfPrjParams[2],
              (padfPrjParams[8] != 0.0) ? padfPrjParams[8] : 1.0,
              padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "ROB"))
    {
        SetRobinson(padfPrjParams[2], padfPrjParams[6], padfPrjParams[7]);
    }

    else if (STARTS_WITH_CI(pszProj, "SGDO"))
    {
        SetOS(padfPrjParams[3], padfPrjParams[2],
              (padfPrjParams[8] != 0.0) ? padfPrjParams[8] : 1.0,
              padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "SG"))
    {
        SetStereographic(padfPrjParams[3], padfPrjParams[2],
                         (padfPrjParams[8] != 0.0) ? padfPrjParams[8] : 1.0,
                         padfPrjParams[6], padfPrjParams[7]);
    }
    else if (STARTS_WITH_CI(pszProj, "SIN"))
    {
        SetSinusoidal(padfPrjParams[2], padfPrjParams[6], padfPrjParams[7]);
    }
    // FIXME: SOM --- Space Oblique Mercator skipped.
    else if (STARTS_WITH_CI(pszProj, "SPCS"))
    {
        const int iZone =
            static_cast<int>(CPLScanLong(const_cast<char *>(pszProj) + 5, 4));

        SetStatePlane(iZone, !bIsNAD27);
        SetLinearUnitsAndUpdateParameters(SRS_UL_METER, 1.0);
    }
    else if (STARTS_WITH_CI(pszProj, "SPIF"))
    {
        const int iZone =
            static_cast<int>(CPLScanLong(const_cast<char *>(pszProj) + 5, 4));

        SetStatePlane(iZone, !bIsNAD27);
        SetLinearUnitsAndUpdateParameters(SRS_UL_FOOT,
                                          CPLAtof(SRS_UL_FOOT_CONV));
    }
    else if (STARTS_WITH_CI(pszProj, "SPAF"))
    {
        const int iZone =
            static_cast<int>(CPLScanLong(const_cast<char *>(pszProj) + 5, 4));

        SetStatePlane(iZone, !bIsNAD27);
        SetLinearUnitsAndUpdateParameters(SRS_UL_US_FOOT,
                                          CPLAtof(SRS_UL_US_FOOT_CONV));
    }
    else if (STARTS_WITH_CI(pszProj, "TM"))
    {
        SetTM(padfPrjParams[3], padfPrjParams[2],
              (padfPrjParams[8] != 0.0) ? padfPrjParams[8] : 1.0,
              padfPrjParams[6], padfPrjParams[7]);
    }

    else if (STARTS_WITH_CI(pszProj, "UTM"))
    {
        bool bNorth = true;

        int iZone =
            static_cast<int>(CPLScanLong(const_cast<char *>(pszProj) + 4, 5));
        if (iZone < 0)
        {
            iZone = -iZone;
            bNorth = false;
        }

        // Check for a zone letter. PCI uses, accidentally, MGRS
        // type row lettering in its UTM projection.
        char byZoneID = 0;

        if (strlen(pszProj) > 10 && pszProj[10] != ' ')
            byZoneID = pszProj[10];

        // Determine if the MGRS zone falls above or below the equator.
        if (byZoneID != 0)
        {
            CPLDebug("OSR_PCI", "Found MGRS zone in UTM projection string: %c",
                     byZoneID);

            if (byZoneID >= 'N' && byZoneID <= 'X')
            {
                bNorth = true;
            }
            else if (byZoneID >= 'C' && byZoneID <= 'M')
            {
                bNorth = false;
            }
            else
            {
                // Yikes.  Most likely we got something that was not really
                // an MGRS zone code so we ignore it.
            }
        }

        SetUTM(iZone, bNorth);
    }
    else if (STARTS_WITH_CI(pszProj, "VDG"))
    {
        SetVDG(padfPrjParams[2], padfPrjParams[6], padfPrjParams[7]);
    }
    else
    {
        CPLDebug("OSR_PCI", "Unsupported projection: %s", pszProj);
        SetLocalCS(pszProj);
    }

    /* ==================================================================== */
    /*      Translate the datum/spheroid.                                   */
    /* ==================================================================== */

    /* -------------------------------------------------------------------- */
    /*      We have an earthmodel string, look it up in the datum list.     */
    /* -------------------------------------------------------------------- */
    if (strlen(szEarthModel) > 0 &&
        (GetRoot() == nullptr || IsProjected() || IsGeographic()))
    {
        const PCIDatums *pasDatum = asDatums;

        // Search for matching datum.
        while (pasDatum->pszPCIDatum)
        {
            if (EQUALN(szEarthModel, pasDatum->pszPCIDatum, 4))
            {
                OGRSpatialReference oGCS;
                oGCS.importFromEPSG(pasDatum->nEPSGCode);
                CopyGeogCSFrom(&oGCS);
                break;
            }
            pasDatum++;
        }

        /* --------------------------------------------------------------------
         */
        /*      If we did not find a datum definition in our in-code EPSG */
        /*      lookup table, then try fetching from the pci_datum.txt */
        /*      file. */
        /* --------------------------------------------------------------------
         */
        char **papszDatumDefn = nullptr;

        if (!pasDatum->pszPCIDatum && szEarthModel[0] == 'D')
        {
            const char *pszDatumCSV = CSVFilename("pci_datum.txt");
            VSILFILE *fp = pszDatumCSV ? VSIFOpenL(pszDatumCSV, "r") : nullptr;

            if (fp != nullptr)
            {
                char **papszLineItems = nullptr;

                while ((papszLineItems = CSVReadParseLineL(fp)) != nullptr)
                {
                    if (CSLCount(papszLineItems) > 3 &&
                        EQUALN(papszLineItems[0], szEarthModel,
                               sizeof(szEarthModel) - 1))
                    {
                        papszDatumDefn = papszLineItems;
                        strncpy(szEarthModel, papszLineItems[2],
                                sizeof(szEarthModel) - 1);
                        break;
                    }
                    CSLDestroy(papszLineItems);
                }

                VSIFCloseL(fp);
            }
        }

        /* --------------------------------------------------------------------
         */
        /*      If not, look in the ellipsoid/EPSG matching list. */
        /* --------------------------------------------------------------------
         */
        if (!pasDatum->pszPCIDatum)  // No matching; search for ellipsoids.
        {
            char *pszName = nullptr;
            double dfSemiMajor = 0.0;
            double dfInvFlattening = 0.0;
            int nEPSGCode = 0;

            pasDatum = asEllips;

            while (pasDatum->pszPCIDatum)
            {
                if (EQUALN(szEarthModel, pasDatum->pszPCIDatum, 4))
                {
                    nEPSGCode = pasDatum->nEPSGCode;
                    CPL_IGNORE_RET_VAL(
                        OSRGetEllipsoidInfo(pasDatum->nEPSGCode, &pszName,
                                            &dfSemiMajor, &dfInvFlattening));
                    break;
                }
                pasDatum++;
            }

            /* --------------------------------------------------------------------
             */
            /*      If we don't find it in that list, do a lookup in the */
            /*      pci_ellips.txt file. */
            /* --------------------------------------------------------------------
             */
            if (!pasDatum->pszPCIDatum && szEarthModel[0] == 'E')
            {
                const char *pszCSV = CSVFilename("pci_ellips.txt");
                VSILFILE *fp = pszCSV ? VSIFOpenL(pszCSV, "r") : nullptr;

                if (fp != nullptr)
                {
                    char **papszLineItems = nullptr;

                    while ((papszLineItems = CSVReadParseLineL(fp)) != nullptr)
                    {
                        if (CSLCount(papszLineItems) > 3 &&
                            EQUALN(papszLineItems[0], szEarthModel, 4))
                        {
                            dfSemiMajor = CPLAtof(papszLineItems[2]);
                            const double dfSemiMinor =
                                CPLAtof(papszLineItems[3]);
                            dfInvFlattening =
                                OSRCalcInvFlattening(dfSemiMajor, dfSemiMinor);
                            break;
                        }
                        CSLDestroy(papszLineItems);
                    }
                    CSLDestroy(papszLineItems);

                    VSIFCloseL(fp);
                }
            }

            /* --------------------------------------------------------------------
             */
            /*      Custom spheroid? */
            /* --------------------------------------------------------------------
             */
            if (dfSemiMajor == 0.0 && STARTS_WITH_CI(szEarthModel, "E999") &&
                padfPrjParams[0] != 0.0)
            {
                dfSemiMajor = padfPrjParams[0];
                double dfSemiMinor = padfPrjParams[1];
                dfInvFlattening =
                    OSRCalcInvFlattening(dfSemiMajor, dfSemiMinor);
            }

            /* --------------------------------------------------------------------
             */
            /*      If nothing else, fall back to WGS84 parameters. */
            /* --------------------------------------------------------------------
             */
            if (dfSemiMajor == 0.0)
            {
                dfSemiMajor = SRS_WGS84_SEMIMAJOR;
                dfInvFlattening = SRS_WGS84_INVFLATTENING;
            }

            /* --------------------------------------------------------------------
             */
            /*      Now try to put this all together into a GEOGCS definition.
             */
            /* --------------------------------------------------------------------
             */

            CPLString osEllipseName;
            if (pszName)
                osEllipseName = pszName;
            else
                osEllipseName.Printf("Unknown - PCI %s", szEarthModel);
            CPLFree(pszName);

            CPLString osDatumName;
            if (papszDatumDefn)
                osDatumName = papszDatumDefn[1];
            else
                osDatumName.Printf("Unknown - PCI %s", szEarthModel);

            const CPLString osGCSName = osDatumName;

            SetGeogCS(osGCSName, osDatumName, osEllipseName, dfSemiMajor,
                      dfInvFlattening);

            // Do we have an ellipsoid EPSG code?
            if (nEPSGCode != 0)
                SetAuthority("SPHEROID", "EPSG", nEPSGCode);

            // Do we have 7 datum shift parameters?
            if (papszDatumDefn != nullptr && CSLCount(papszDatumDefn) >= 15 &&
                CPLAtof(papszDatumDefn[14]) != 0.0)
            {
                double dfScale = CPLAtof(papszDatumDefn[14]);

                // we want scale in parts per million off 1.0
                // but pci uses a mix of forms.
                if (dfScale >= 0.999 && dfScale <= 1.001)
                    dfScale = (dfScale - 1.0) * 1000000.0;

                SetTOWGS84(
                    CPLAtof(papszDatumDefn[3]), CPLAtof(papszDatumDefn[4]),
                    CPLAtof(papszDatumDefn[5]), CPLAtof(papszDatumDefn[11]),
                    CPLAtof(papszDatumDefn[12]), CPLAtof(papszDatumDefn[13]),
                    dfScale);
            }

            // Do we have 7 datum shift parameters?
            else if (papszDatumDefn != nullptr &&
                     CSLCount(papszDatumDefn) == 11 &&
                     (CPLAtof(papszDatumDefn[3]) != 0.0 ||
                      CPLAtof(papszDatumDefn[4]) != 0.0 ||
                      CPLAtof(papszDatumDefn[5]) != 0.0))
            {
                SetTOWGS84(CPLAtof(papszDatumDefn[3]),
                           CPLAtof(papszDatumDefn[4]),
                           CPLAtof(papszDatumDefn[5]));
            }
        }

        CSLDestroy(papszDatumDefn);
    }

    /* -------------------------------------------------------------------- */
    /*      Grid units translation                                          */
    /* -------------------------------------------------------------------- */
    if ((IsLocal() || IsProjected()) && pszUnits)
    {
        if (EQUAL(pszUnits, "METRE"))
            SetLinearUnits(SRS_UL_METER, 1.0);
        else if (EQUAL(pszUnits, "DEGREE"))
            SetAngularUnits(SRS_UA_DEGREE, CPLAtof(SRS_UA_DEGREE_CONV));
        else
            SetLinearUnits(SRS_UL_METER, 1.0);
    }

    return OGRERR_NONE;
}

/************************************************************************/
/*                          OSRExportToPCI()                            */
/************************************************************************/
/**
 * \brief Export coordinate system in PCI projection definition.
 *
 * This function is the same as OGRSpatialReference::exportToPCI().
 */
OGRErr OSRExportToPCI(OGRSpatialReferenceH hSRS, char **ppszProj,
                      char **ppszUnits, double **ppadfPrjParams)

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

    *ppszProj = nullptr;
    *ppszUnits = nullptr;
    *ppadfPrjParams = nullptr;

    return OGRSpatialReference::FromHandle(hSRS)->exportToPCI(
        ppszProj, ppszUnits, ppadfPrjParams);
}

/************************************************************************/
/*                           exportToPCI()                              */
/************************************************************************/

/**
 * \brief Export coordinate system in PCI projection definition.
 *
 * Converts the loaded coordinate reference system into PCI projection
 * definition to the extent possible. The strings returned in ppszProj,
 * ppszUnits and ppadfPrjParams array should be deallocated by the caller
 * with CPLFree() when no longer needed.
 *
 * LOCAL_CS coordinate systems are not translatable.  An empty string
 * will be returned along with OGRERR_NONE.
 *
 * This method is the equivalent of the C function OSRExportToPCI().
 *
 * @param ppszProj pointer to which dynamically allocated PCI projection
 * definition will be assigned.
 *
 * @param ppszUnits pointer to which dynamically allocated units definition
 * will be assigned.
 *
 * @param ppadfPrjParams pointer to which dynamically allocated array of
 * 17 projection parameters will be assigned. See importFromPCI() for the list
 * of parameters.
 *
 * @return OGRERR_NONE on success or an error code on failure.
 */

OGRErr OGRSpatialReference::exportToPCI(char **ppszProj, char **ppszUnits,
                                        double **ppadfPrjParams) const

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

    /* -------------------------------------------------------------------- */
    /*      Fill all projection parameters with zero.                       */
    /* -------------------------------------------------------------------- */
    *ppadfPrjParams = static_cast<double *>(CPLMalloc(17 * sizeof(double)));
    for (int i = 0; i < 17; i++)
        (*ppadfPrjParams)[i] = 0.0;

/* -------------------------------------------------------------------- */
/*      Get the prime meridian info.                                    */
/* -------------------------------------------------------------------- */
#if 0
    const OGR_SRSNode *poPRIMEM = GetAttrNode( "PRIMEM" );
    double dfFromGreenwich = 0.0;

    if( poPRIMEM != NULL && poPRIMEM->GetChildCount() >= 2
        && CPLAtof(poPRIMEM->GetChild(1)->GetValue()) != 0.0 )
    {
        dfFromGreenwich = CPLAtof(poPRIMEM->GetChild(1)->GetValue());
    }
#endif

    /* ==================================================================== */
    /*      Handle the projection definition.                               */
    /* ==================================================================== */
    char szProj[knProjSize + 1] = {};

    if (IsLocal())
    {
        if (GetLinearUnits() > 0.30479999 && GetLinearUnits() < 0.3048010)
            CPLPrintStringFill(szProj, "FEET", knProjSize);
        else
            CPLPrintStringFill(szProj, "METER", knProjSize);
    }
    else if (pszProjection == nullptr)
    {
        CPLPrintStringFill(szProj, "LONG/LAT", knProjSize);
    }
    else if (EQUAL(pszProjection, SRS_PT_ALBERS_CONIC_EQUAL_AREA))
    {
        CPLPrintStringFill(szProj, "ACEA", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0);
        (*ppadfPrjParams)[4] = GetNormProjParm(SRS_PP_STANDARD_PARALLEL_1, 0.0);
        (*ppadfPrjParams)[5] = GetNormProjParm(SRS_PP_STANDARD_PARALLEL_2, 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))
    {
        CPLPrintStringFill(szProj, "AE", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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_CASSINI_SOLDNER))
    {
        CPLPrintStringFill(szProj, "CASS", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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))
    {
        CPLPrintStringFill(szProj, "EC", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_LONGITUDE_OF_CENTER, 0.0);
        (*ppadfPrjParams)[3] = GetNormProjParm(SRS_PP_LATITUDE_OF_CENTER, 0.0);
        (*ppadfPrjParams)[4] = GetNormProjParm(SRS_PP_STANDARD_PARALLEL_1, 0.0);
        (*ppadfPrjParams)[5] = GetNormProjParm(SRS_PP_STANDARD_PARALLEL_2, 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))
    {
        CPLPrintStringFill(szProj, "ER", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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_GNOMONIC))
    {
        CPLPrintStringFill(szProj, "GNO", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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))
    {
        CPLPrintStringFill(szProj, "LAEA", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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))
    {
        CPLPrintStringFill(szProj, "LCC", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0);
        (*ppadfPrjParams)[4] = GetNormProjParm(SRS_PP_STANDARD_PARALLEL_1, 0.0);
        (*ppadfPrjParams)[5] = GetNormProjParm(SRS_PP_STANDARD_PARALLEL_2, 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_1SP))
    {
        CPLPrintStringFill(szProj, "LCC_1SP", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = GetNormProjParm(SRS_PP_LATITUDE_OF_ORIGIN, 0.0);
        (*ppadfPrjParams)[8] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
        (*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))
    {
        CPLPrintStringFill(szProj, "MC", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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))
    {
        CPLPrintStringFill(szProj, "MER", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
    }
    else if (EQUAL(pszProjection, SRS_PT_ORTHOGRAPHIC))
    {
        CPLPrintStringFill(szProj, "OG", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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_HOTINE_OBLIQUE_MERCATOR))
    {
        CPLPrintStringFill(szProj, "OM", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_LONGITUDE_OF_CENTER, 0.0);
        (*ppadfPrjParams)[3] = GetNormProjParm(SRS_PP_LATITUDE_OF_CENTER, 0.0);
        (*ppadfPrjParams)[14] = GetNormProjParm(SRS_PP_AZIMUTH, 0.0);
        // Note: Ignoring rectified_grid_angle which has no PCI analog.
        (*ppadfPrjParams)[8] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 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_TWO_POINT_NATURAL_ORIGIN))
    {
        CPLPrintStringFill(szProj, "OM", knProjSize);
        (*ppadfPrjParams)[3] = GetNormProjParm(SRS_PP_LATITUDE_OF_CENTER, 0.0);
        (*ppadfPrjParams)[11] =
            GetNormProjParm(SRS_PP_LATITUDE_OF_POINT_1, 0.0);
        (*ppadfPrjParams)[10] =
            GetNormProjParm(SRS_PP_LONGITUDE_OF_POINT_1, 0.0);
        (*ppadfPrjParams)[13] =
            GetNormProjParm(SRS_PP_LATITUDE_OF_POINT_2, 0.0);
        (*ppadfPrjParams)[12] =
            GetNormProjParm(SRS_PP_LONGITUDE_OF_POINT_2, 0.0);
        (*ppadfPrjParams)[8] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 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))
    {
        CPLPrintStringFill(szProj, "PC", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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))
    {
        CPLPrintStringFill(szProj, "PS", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
    }
    else if (EQUAL(pszProjection, SRS_PT_ROBINSON))
    {
        CPLPrintStringFill(szProj, "ROB", knProjSize);
        (*ppadfPrjParams)[2] = 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_OBLIQUE_STEREOGRAPHIC))
    {
        CPLPrintStringFill(szProj, "SGDO", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
    }
    else if (EQUAL(pszProjection, SRS_PT_STEREOGRAPHIC))
    {
        CPLPrintStringFill(szProj, "SG", knProjSize);
        (*ppadfPrjParams)[2] = GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
        (*ppadfPrjParams)[3] = 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] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
    }
    else if (EQUAL(pszProjection, SRS_PT_SINUSOIDAL))
    {
        CPLPrintStringFill(szProj, "SIN", knProjSize);
        (*ppadfPrjParams)[2] = 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_TRANSVERSE_MERCATOR))
    {
        int bNorth = FALSE;
        int nZone = GetUTMZone(&bNorth);

        if (nZone != 0)
        {
            CPLPrintStringFill(szProj, "UTM", knProjSize);
            if (bNorth)
                CPLPrintInt32(szProj + 5, nZone, 4);
            else
                CPLPrintInt32(szProj + 5, -nZone, 4);
        }
        else
        {
            CPLPrintStringFill(szProj, "TM", knProjSize);
            (*ppadfPrjParams)[2] =
                GetNormProjParm(SRS_PP_CENTRAL_MERIDIAN, 0.0);
            (*ppadfPrjParams)[3] =
                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] = GetNormProjParm(SRS_PP_SCALE_FACTOR, 1.0);
        }
    }
    else if (EQUAL(pszProjection, SRS_PT_VANDERGRINTEN))
    {
        CPLPrintStringFill(szProj, "VDG", knProjSize);
        (*ppadfPrjParams)[2] = 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);
    }
    // Projection unsupported by PCI.
    else
    {
        CPLDebug("OSR_PCI",
                 "Projection \"%s\" unsupported by PCI. "
                 "PIXEL value will be used.",
                 pszProjection);
        CPLPrintStringFill(szProj, "PIXEL", knProjSize);
    }

    /* ==================================================================== */
    /*      Translate the earth model.                                      */
    /* ==================================================================== */

    /* -------------------------------------------------------------------- */
    /*      Is this a well known datum?                                     */
    /* -------------------------------------------------------------------- */
    const char *pszDatum = GetAttrValue("DATUM");
    char szEarthModel[5] = {};

    if (pszDatum == nullptr || strlen(pszDatum) == 0)
    {
        // Do nothing.
    }
    else if (EQUAL(pszDatum, SRS_DN_NAD27))
    {
        CPLPrintStringFill(szEarthModel, "D-01", 4);
    }
    else if (EQUAL(pszDatum, SRS_DN_NAD83))
    {
        CPLPrintStringFill(szEarthModel, "D-02", 4);
    }
    else if (EQUAL(pszDatum, SRS_DN_WGS84))
    {
        CPLPrintStringFill(szEarthModel, "D000", 4);
        if (pszProjection && EQUAL(pszProjection, SRS_PT_MERCATOR_1SP))
        {
            // Special case for Web Mercator
            const char *method_name = "";
            GetWKT2ProjectionMethod(&method_name, nullptr, nullptr);
            if (EQUAL(method_name, "Popular Visualisation Pseudo Mercator"))
            {
                CPLPrintStringFill(szEarthModel, "D894", 4);
            }
        }
    }

    /* -------------------------------------------------------------------- */
    /*      If not a very well known datum, try for an EPSG based           */
    /*      translation.                                                    */
    /* -------------------------------------------------------------------- */
    if (szEarthModel[0] == '\0')
    {
        const char *pszAuthority = GetAuthorityName("GEOGCS");

        if (pszAuthority && EQUAL(pszAuthority, "EPSG"))
        {
            const int nGCS_EPSG = atoi(GetAuthorityCode("GEOGCS"));

            for (int i = 0; asDatums[i].nEPSGCode != 0; i++)
            {
                if (asDatums[i].nEPSGCode == nGCS_EPSG)
                {
                    snprintf(szEarthModel, sizeof(szEarthModel), "%s",
                             asDatums[i].pszPCIDatum);
                    break;
                }
            }
        }
    }

    /* -------------------------------------------------------------------- */
    /*      If we haven't found something yet, try translating the          */
    /*      ellipsoid.                                                      */
    /* -------------------------------------------------------------------- */
    const double dfSemiMajor = GetSemiMajor();
    const double dfInvFlattening = GetInvFlattening();
    if (szEarthModel[0] == '\0')
    {
        const PCIDatums *pasDatum = asEllips;

        while (pasDatum->pszPCIDatum)
        {
            double dfSM = 0.0;
            double dfIF = 0.0;

            if (OSRGetEllipsoidInfo(pasDatum->nEPSGCode, nullptr, &dfSM,
                                    &dfIF) == OGRERR_NONE &&
                CPLIsEqual(dfSemiMajor, dfSM) &&
                CPLIsEqual(dfInvFlattening, dfIF))
            {
                CPLPrintStringFill(szEarthModel, pasDatum->pszPCIDatum, 4);
                break;
            }

            pasDatum++;
        }
    }

    // Try to find in pci_ellips.txt.
    if (szEarthModel[0] == '\0')
    {
        const char *pszCSV = CSVFilename("pci_ellips.txt");
        const double dfSemiMinor =
            OSRCalcSemiMinorFromInvFlattening(dfSemiMajor, dfInvFlattening);

        VSILFILE *fp = pszCSV ? VSIFOpenL(pszCSV, "r") : nullptr;

        if (fp != nullptr)
        {
            char **papszLineItems = nullptr;

            while ((papszLineItems = CSVReadParseLineL(fp)) != nullptr)
            {
                if (CSLCount(papszLineItems) >= 4 &&
                    CPLIsEqual(dfSemiMajor, CPLAtof(papszLineItems[2])) &&
                    CPLIsEqual(dfSemiMinor, CPLAtof(papszLineItems[3])))
                {
                    snprintf(szEarthModel, sizeof(szEarthModel), "%s",
                             papszLineItems[0]);
                    break;
                }

                CSLDestroy(papszLineItems);
            }

            CSLDestroy(papszLineItems);
            VSIFCloseL(fp);
        }
    }

    // Custom ellipsoid parameters.
    if (szEarthModel[0] == '\0')
    {
        CPLPrintStringFill(szEarthModel, "E999", 4);
        (*ppadfPrjParams)[0] = dfSemiMajor;
        (*ppadfPrjParams)[1] =
            OSRCalcSemiMinorFromInvFlattening(dfSemiMajor, dfInvFlattening);
    }

    /* -------------------------------------------------------------------- */
    /*      If we have a non-parameteric ellipsoid, scan the                */
    /*      pci_datum.txt for a match.                                      */
    /* -------------------------------------------------------------------- */
    if (szEarthModel[0] == 'E' && !EQUAL(szEarthModel, "E999") &&
        pszDatum != nullptr)
    {
        const char *pszDatumCSV = CSVFilename("pci_datum.txt");
        double adfTOWGS84[7] = {};
        const bool bHaveTOWGS84 = GetTOWGS84(adfTOWGS84, 7) == OGRERR_NONE;

        VSILFILE *fp = pszDatumCSV ? VSIFOpenL(pszDatumCSV, "r") : nullptr;

        if (fp != nullptr)
        {
            char **papszLineItems = nullptr;

            while ((papszLineItems = CSVReadParseLineL(fp)) != nullptr)
            {
                // Compare based on datum name.  This is mostly for
                // PCI round-tripping.  We won't usually get exact matches
                // from other sources.
                if (CSLCount(papszLineItems) > 3 &&
                    EQUAL(papszLineItems[1], pszDatum) &&
                    EQUAL(papszLineItems[2], szEarthModel))
                {
                    snprintf(szEarthModel, sizeof(szEarthModel), "%s",
                             papszLineItems[0]);
                    break;
                }

                bool bTOWGS84Match = bHaveTOWGS84;

                if (CSLCount(papszLineItems) < 11)
                    bTOWGS84Match = false;

                if (bTOWGS84Match &&
                    (!CPLIsEqual(adfTOWGS84[0], CPLAtof(papszLineItems[3])) ||
                     !CPLIsEqual(adfTOWGS84[1], CPLAtof(papszLineItems[4])) ||
                     !CPLIsEqual(adfTOWGS84[2], CPLAtof(papszLineItems[5]))))
                    bTOWGS84Match = false;

                if (bTOWGS84Match && CSLCount(papszLineItems) >= 15 &&
                    (!CPLIsEqual(adfTOWGS84[3], CPLAtof(papszLineItems[11])) ||
                     !CPLIsEqual(adfTOWGS84[4], CPLAtof(papszLineItems[12])) ||
                     !CPLIsEqual(adfTOWGS84[5], CPLAtof(papszLineItems[13]))))
                    bTOWGS84Match = false;

                if (bTOWGS84Match && CSLCount(papszLineItems) >= 15)
                {
                    double dfScale = CPLAtof(papszLineItems[14]);

                    // Convert to parts per million if is a 1 based scaling.
                    if (dfScale >= 0.999 && dfScale <= 1.001)
                        dfScale = (dfScale - 1.0) * 1000000.0;

                    if (fabs(adfTOWGS84[6] - dfScale) >
                        1e-11 * fabs(adfTOWGS84[6]))
                        bTOWGS84Match = false;
                }

                if (bTOWGS84Match && CSLCount(papszLineItems) < 15 &&
                    (!CPLIsEqual(adfTOWGS84[3], 0.0) ||
                     !CPLIsEqual(adfTOWGS84[4], 0.0) ||
                     !CPLIsEqual(adfTOWGS84[5], 0.0) ||
                     !CPLIsEqual(adfTOWGS84[6], 0.0)))
                    bTOWGS84Match = false;

                if (bTOWGS84Match)
                {
                    snprintf(szEarthModel, sizeof(szEarthModel), "%s",
                             papszLineItems[0]);
                    break;
                }

                CSLDestroy(papszLineItems);
            }

            CSLDestroy(papszLineItems);
            VSIFCloseL(fp);
        }
    }

    CPLPrintStringFill(szProj + 12, szEarthModel, 4);

    CPLDebug("OSR_PCI", "Translated as '%s'", szProj);

    /* -------------------------------------------------------------------- */
    /*      Translate the linear units.                                     */
    /* -------------------------------------------------------------------- */
    const char *pszUnits =
        STARTS_WITH_CI(szProj, "LONG/LAT") ? "DEGREE" : "METRE";

    /* -------------------------------------------------------------------- */
    /*      Report results.                                                 */
    /* -------------------------------------------------------------------- */
    szProj[knProjSize] = '\0';
    *ppszProj = CPLStrdup(szProj);

    *ppszUnits = CPLStrdup(pszUnits);

    return OGRERR_NONE;
}