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Integrating ACUF and GEBCO Gazetteers Into Marine Regions Pg

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Integrating ACUF and GEBCO Gazetteers Into Marine Regions Pg Integrating ACUF and GEBCO gazetteers into Marine Regions 1. Introduction ACUF (Advisory Committee on Undersea Features) is part of the United States Board on Geographic Names (BGN), and was established This report summarises the approach to recommend standardization policy for undertaken to integrate ACUF and GEBCO data names of undersea features. into Marine Regions, highlighting the different issues encountered and how these have been The GEBCO (General Bathymetric Chart of the managed. The purpose of Marine Regions is to Oceans) Sub-Committee on Undersea Feature Names (SCUFN) maintains and makes available a create a standard, relational list of geographic digital gazetteer of the names, generic names, coupled with information and maps of feature type and geographic position of the geographic location of these features. features on the sea floor. 2. Methodology: the Geo-object approach In the Marine Regions database each geographic entity, a Geo-object, is defined by: - The coordinates (lat-long, calculated if the feature is a polygon, polyline or multipoint). - The place type (bay, trench, seamount, anchorage, etc.). - But it can have different names (synonym in original language, etc.). Coordinates (lat-long) Place type Place name(s) Geo-object = + x=17.13° Cape Johnson Guyot y=-177.25° Cape Johnson Tablemount With this in mind and with the purpose of detecting the geo-objects which might be already present in the Marine Regions database, different scenarios have been identified which are summarised in the table below. We therefore have to look at each of these attributes (place type, place name and coordinates) for every record within ACUF and GEBCO datasets and compare them to the Marine Regions records. pg. 1 Coord. Place Place Feature Action (x,y) type name Same This is a record that already exists in Marine 1 Equal Equal Equal feature Regions. Add context and synonym if relevant. Probably This could be a synonym of an existing feature (to 2 Equal Equal Different same be added if relevant). It can also be a different feature feature. Some discrepancy in coordinates can be expected Probably for the same feature. Add context and synonym if 3 Similar Equal Equal same relevant. It can also be a different feature, and a feature new geo-object has to be created. Multipoint/ Probably A special case for features not represented as points 4 Polyline/ Equal Equal same in GEBCO, when the calculated central point does Polygon feature not match the ACUF coordinates. Different 5 Equal Different Equal A new geo-object has to be created. feature Different A new geo-object needs to be added to Marine 6 Different Equal Equal feature Regions. 7 Similar Equal Different ?? Needs to be checked 2.1. Place types The definition of marine features is not always straightforward and in some instances a different synonym can be used to express the same type of feature (e.g. guyot and tablemount). It is necessary to standardise the place types used by the different gazetteers. The definitions of the different feature types provided by ACUF and GEBCO have been compared and matched to those in MR. Some issues have been found in relation to the compatibility or consistency between the definitions provided by the three gazetteers, which are detailed in Appendix 1d. Besides, the cases in which certain place types are not used anymore, they are used but a definition is not given or the place type assigned seems incorrect have been documented (Appendix 1a, 1b and 1c). 2.2. Place names 2.1.1. ACUF Different synonyms for the same feature appear in the ACUF dataset has separate records that share the same value for the [UFI] field (Undersea Feature Identifier). The table has been compressed by inserting the synonyms and their unique attributes into adjacent columns (figure below) by a series of iterative queries, basing the join in the [UFI] field. This way the number of records is reduced from 10196 to 5027. Integrating ACUF and GEBCO gazetteers into Marine Regions pg. 2 In Marine Regions, for each geographic entity and the available synonyms the place name language is provided. Within the ACUF records, the synonym appears with a language code associated in some cases. In others, however, the language will have to be added manually if known (whether it is a new geo-object or a synonym of an existing feature), or the ‘Uncertain language’ code will be added. 2.2.2. GEBCO The place name of the features imported from GEBCO are obtained by joining the fields [Specific term] and [Generic term]. Although the specific term might appear in the original language (e.g. Agulhas; Portuguese), the generic term is always in English (e.g. Agulhas bank, Agulhas ridge). 2.3. Coordinates Features in ACUF are represented always as points. However, undersea features in Marine Regions and GEBCO can be represented either as points, multipoints, lines or polygons. This raises some problems with regards to automatizing the comparison of the already existing features in the different gazetteers. Some case examples of the same feature having different coordinates are shown in Appendix 3a and 3b. Integrating ACUF and GEBCO gazetteers into Marine Regions pg. 3 3. Flow chart Integrating ACUF and GEBCO gazetteers into Marine Regions pg. 4 Appendix 1. Issues related to place type definitions and matching. Observations The date of data download: ACUF: 16th May 2014 GEBCO: 8th May 2014 The source for place type and definitions: ACUF: http://geonames.nga.mil/namesgaz/, Look up tables / Designation codes GEBCO: http://www.kosbidb2.co.kr:8080/recommend/ GEBCO place types are shown in the field [Generic Term], whereas for ACUF data these are indicated by a feature designation code in the field [DSG]. Place types and definitions in Marine Regions are undergoing revision. a) The place type exists/is defined but it is not used (does not appear in the records). ACUF GEBCO Abyssal Hill Archipelagic Apron BNCU undersea bench Continental Margin CRSU continental rise Continental Rise FLTU undersea flat Continental shelf FRKU undersea fork Fracture Zone Province FRSU undersea forks Median Valley GLYU undersea gully Mid-Ocean Ridge LDGU undersea ledge Moat LEVU undersea levee Pinnacle MDVU undersea median valley Salt dome MTSU undersea mountains Sand ridge MTU undersea mountain Scarp PKSU undersea peaks Sea valley PLFU undersea platform Shelf break RAVU undersea ravine Zone RMPU undersea ramp Shelf edge RNGU undersea range Submarine valley b) GEBCO. The place type is used but a definition is not given. Several place types have been found for which a definition is not given and that, in most cases, are only used once: Integrating ACUF and GEBCO gazetteers into Marine Regions pg. 5 N˚ of Place type Comments records Basin and ridge province 1 Kobayashi Basin and ridge province Flemish Cap Cap 1 Gap? There is also a place type ‘Sea channel’ (with space) with 1 Seachannel 32 record. Sea channel = Seachannel! Continental Slope 1 Aktivneset Continental Slope Discordance 1 Australian-Antarctic Discordance Eltanin Fracture Zone System Fracture Zone System 1 Fracture zone? Ground 1 Fairweather Ground Pass (Passage?) Flemish Pass 1 Plain (Abyssal plain) Passage? Seabight 1 Porcupine Seabight Marcus-Wake Seamount Group Seamount Group 1 Seamounts? C&GS Seamount Province Seamount Province 3 Gulf of Alaska Seamount Province Baja California Seamount Province c) ACUF. The feature code assigned to the geographic entity seems incorrect. For the meaning of the code and the definition of the each place type a table can be downloaded at http://geonames.nga.mil/namesgaz/. The undersea features are recognisable because the [Feature Class] field is filled with ‘U – Undersea’. However, for the following entities, the feature code assigned does not belong to the Undersea feature class: Feat. Place Feature desig. Definition Records Should be…? type class code That part of a body of water deep CHNM Marine H - -North Sahul enough for navigation through an SEACHANNEL channel Hydrographic Passage area otherwise not suitable. A surface-navigation hazard H - RFSU (Reefs) or RF Reef(s) -Star Reefs composed of consolidated material. Hydrographic RFU (Reef) A surface-navigation hazard H - SHLU (Shoal) or SHOL Shoal(s) composed of unconsolidated -Bellona Bank Hydrographic SHSU (Shoals) material A long, narrow alluvial platform -Kucherov bounded by steeper slopes above T - Terrace TRR Terrace ??? and below, usually overlooking a Hypsographic -Voronov waterbody. Terrace Integrating ACUF and GEBCO gazetteers into Marine Regions pg. 6 d) Incompatible or inconsistent definitions. Place type Hill(s) ID 62 MR Definition An isolated (or group of) elevation(s), smaller than a SEAMOUNT. An area of upland smaller than a mountain but with no specific definition of absolute elevation Place type Hill / Hills GEBCO Definition A distinct elevation generally of irregular shape, less than 1000m above the surrounding relief as measured from the deepest isobath that surrounds most of the feature. Place type Hill / hills ACUF ID HLLU / HLSU Definition an elevation rising generally less than 500 meters Place type Knoll(s) ID 84 MR Definition An elevation somewhat smaller than a SEAMOUNT and of rounded profile, characteristically isolated or as a cluster on the sea floor. A rounded hill of no great elevation. Place type Knoll / Knolls GEBCO Definition A distinct elevation with a rounded profile less than 1000m above the surrounding relief as measured from the deepest isobath that surrounds most of the feature. Place type Knoll / Knolls ID KNLU / KNSU ACUF Definition an elevation rising generally more than 500 meters and less than 1,000 meters and of limited extent across the summit Place type Sill ID 113 Definition A sea floor barrier of relatively shallow depth restricting water movement between MR BASINS. • An intrusive body of solidified magma, that has been ejected as a near-horizontal sheet between the bedding-planes of the crustal rocks • A submarine bar or ridge across the mouth of a fjord Place type Sill GEBCO Definition The sloping region that deepens from a SHELF to the point where there is a general decrease in gradient.
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