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MARC PROPOSAL NO. 2010-08

DATE: May 17, 2010
REVISED:

NAME: Encoding Scheme of Coordinate Data in Field 034 (Coded Cartographic Mathematical Data) of the MARC 21 Bibliographic and Authority Formats

SOURCE: Library of Congress

SUMMARY: This paper proposes adding a subfield to field 034 to specify the type of encoding scheme used to express coordinate data.

KEYWORDS: Field 034 (BD, AD); Coded Cartographic Mathematical Data (BD, AD); Geographic coordinates (BD, AD); Coordinate encoding scheme (BD, AD)

RELATED:

STATUS/COMMENTS:
5/17/10 – Made available to the MARC community for discussion.

6/26/10 – Results of MARC Advisory Committee discussion: Rejected. It was not clear whether the format of the coordinates was self-identifying and whether this change was necessary. LC will investigate and bring the proposal back if further research determines the need for this change.

08/26/10 - Results of LC/LAC/BL review - Agreed with the MARBI decision.


Proposal No. 2010-08: Encoding Scheme of Coordinate Data in Field 034

1. BACKGROUND

Field 034 (Coded Cartographic Mathematical Data) is defined in the MARC 21 Bibliographic and Authority formats for Cartographic mathematical data, including scale, projection, and coordinates in coded form. Although there are different methods (i.e.  encodings) to express coordinates, the particular method used is not explicit in the field. Commonly used encodings are degrees, minutes, seconds  and decimal degrees; there is also an encoding used by the US military (“mgrs” or Military grade reference system). Systems can often translate between these encodings, but it would be useful for processing large amounts of data if the information were explicit.  Much attention has been paid to geospatial data on the Internet and coordinates are the mechanism used to place geographic areas in their context and show locations on a map. This paper discusses the possibility of defining such a subfield in field 034.

2. DISCUSSION

2.1 Coordinates in field 034

Field 034 is used in both the Bibliographic and Authority formats for coordinate data. The following subfields are defined in the Bibliographic format:

First indicator
Type of scale
0 - Scale indeterminable/No scale recorded
1 - Single scale
3 - Range of scales

Second indicator
Type of ring
# - Not applicable
0 - Outer ring
1 - Exclusion ring

Subfields
$a - Category of scale (NR)
$b - Constant ratio linear horizontal scale (R)
$c - Constant ratio linear vertical scale (R)
$d - Coordinates - westernmost longitude (NR)
$e - Coordinates - easternmost longitude (NR)
$f - Coordinates - northernmost latitude (NR)
$g - Coordinates - southernmost latitude (NR)
$h - Angular scale (R)
$j - Declination - northern limit (NR)
$k - Declination - southern limit (NR)
$m - Right ascension - eastern limit (NR)
$n - Right ascension - western limit (NR)
$p - Equinox (NR)
$r - Distance from earth (NR)
$s - G-ring latitude (R)
$t - G-ring longitude (R)
$x - Beginning date (NR)
$y - Ending date (NR)
$z - Name of extraterrestrial body (NR)
$2 - Source (NR)
$3 - Materials specified (NR)
$6 - Linkage (NR)
$8 - Field link and sequence number (R)

In the Authority format not all the subfields are defined that are in the Bibliographic format, since scale is not applicable to the place entities described in authority records.

Coordinates are recorded in subfields $d, $e, $f $g, $s and $t. The format specifies the following:

“The coordinates may be recorded in the form hdddmmss (hemisphere-degrees-minutes-seconds), however, other forms are also allowed, such as decimal degrees. The subelements are each right justified and unused positions contain zeros.”

Examples of the two encodings are:
degrees/minutes/seconds: hdddmmss (hemisphere-degrees-minutes-seconds):
034 1# $dW1800000$eE1800000$fN0840000$gS0700000

decimal degrees: hddd.dddddd (hemisphere-degrees.decimal degrees):
034 1# $dE079.533265$eE086.216635$fS012.583377$gS020.419532

decimal degrees: +-ddd.dddddd (hemisphere[+/-]-degrees.decimal degrees) (“+” for N and E, “-“ for S and W; the plus sign is optional):
034 1# $aa$d+079.533265$e+086.216635$f-012.583377$g-020.419532
Or without the +
034 1# $aa$d079.533265$e086.216635$f-012.583377$g-020.419532

2.2 Defining a subfield for encoding method in field 034

It is preferable to give data about the encoding scheme for coordinates in a controlled form so that they can be interpreted and processed without human intervention.  The information is similar to what is defined in subfield $2 (Source of date) in field 046 (Special Coded Dates), which specifies the date encoding scheme as a code taken from Date and Time Scheme Source Codes.  However, subfield $2 is already defined in field 034 as Source, which identifies the source of information using codes from Cartographic Data Source Codes.

A new subfield could be defined as Coordinate encoding scheme. It is suggested that subfield $7 be used, which has been defined as a control subfield in field 533 (Reproduction note) and 76X-78X (Linking entry fields).  A scheme source code list will be established for the information in a coded form. For instance code “dd” could be used for Decimal degrees and code “dms” for Degrees, minutes, seconds.

3. PROPOSED CHANGES

In the MARC 21 Bibliographic and Authority formats in field 034 (Coded Cartographic Mathematical Data):

Define $7 (Coordinate encoding scheme) as follows:
Code that identifies the encoding scheme for the coordinate data in subfields $d, $e, $f, $g, $s and $t. Code from: Coordinate Scheme Source Codes.


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