ST_GeomFromMARC21

Takes MARC21/XML geographic data as input and returns a PostGIS geometry object.

                        geometry
                        ST_GeomFromMARC21

                        text
                        marcxml

## Description

This function creates a PostGIS geometry from a MARC21/XML record, which can contain a `POINT` or a `POLYGON`. In case of multiple geographic data entries in the same MARC21/XML record, a `MULTIPOINT` or `MULTIPOLYGON` will be returned. If the record contains mixed geometry types, a `GEOMETRYCOLLECTION` will be returned. It returns NULL if the MARC21/XML record does not contain any geographic data (datafield:034).

LOC MARC21/XML versions supported:

- MARC21/XML 1.1

Availability: 3.3.0, requires libxml2 2.6+

The MARC21/XML Coded Cartographic Mathematical Data currently does not provide any means to describe the Spatial Reference System of the encoded coordinates, so this function will always return a geometry with `SRID 0`.

Returned `POLYGON` geometries will always be clockwise oriented.

## Examples

Converting MARC21/XML geographic data containing a single `POINT` encoded as `hddd.dddddd`

                SELECT
                  ST_AsText(
                    ST_GeomFromMARC21('
                        <record xmlns="http://www.loc.gov/MARC21/slim">
                            <leader>00000nz a2200000nc 4500</leader>
                            <controlfield tag="001">040277569</controlfield>
                            <datafield tag="034" ind1=" " ind2=" ">
                                <subfield code="d">W004.500000</subfield>
                                <subfield code="e">W004.500000</subfield>
                                <subfield code="f">N054.250000</subfield>
                                <subfield code="g">N054.250000</subfield>
                            </datafield>
                        </record>'));

                st_astext
                -------------------
                POINT(-4.5 54.25)
                (1 row)

Converting MARC21/XML geographic data containing a single `POLYGON` encoded as `hdddmmss`

                SELECT
                  ST_AsText(
                    ST_GeomFromMARC21('
                        <record xmlns="http://www.loc.gov/MARC21/slim">
                            <leader>01062cem a2200241 a 4500</leader>
                            <controlfield tag="001">   84696781 </controlfield>
                            <datafield tag="034" ind1="1" ind2=" ">
                                <subfield code="a">a</subfield>
                                <subfield code="b">50000</subfield>
                                <subfield code="d">E0130600</subfield>
                                <subfield code="e">E0133100</subfield>
                                <subfield code="f">N0523900</subfield>
                                <subfield code="g">N0522300</subfield>
                            </datafield>
                        </record>'));

                st_astext
                -----------------------------------------------------------------------------------------------------------------------
                POLYGON((13.1 52.65,13.516666666666667 52.65,13.516666666666667 52.38333333333333,13.1 52.38333333333333,13.1 52.65))
                (1 row)

Converting MARC21/XML geographic data containing a `POLYGON` and a `POINT`:

                SELECT
                  ST_AsText(
                    ST_GeomFromMARC21('
                <record xmlns="http://www.loc.gov/MARC21/slim">
                    <datafield tag="034" ind1="1" ind2=" ">
                        <subfield code="a">a</subfield>
                        <subfield code="b">50000</subfield>
                        <subfield code="d">E0130600</subfield>
                        <subfield code="e">E0133100</subfield>
                        <subfield code="f">N0523900</subfield>
                        <subfield code="g">N0522300</subfield>
                    </datafield>
                    <datafield tag="034" ind1=" " ind2=" ">
                        <subfield code="d">W004.500000</subfield>
                        <subfield code="e">W004.500000</subfield>
                        <subfield code="f">N054.250000</subfield>
                        <subfield code="g">N054.250000</subfield>
                    </datafield>
                </record>'));
                                                                                          st_astext
                -------------------------------------------------------------------------------------------------------------------------------------------------------------
                 GEOMETRYCOLLECTION(POLYGON((13.1 52.65,13.516666666666667 52.65,13.516666666666667 52.38333333333333,13.1 52.38333333333333,13.1 52.65)),POINT(-4.5 54.25))
                (1 row)

## See Also

ST_AsMARC21