TDM Location Management System
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Contents |
LOCATION INFORMATION
INTRODUCTION
In ICIS, location information is stored to record the origin or destination of germplasm or the location of sites where information or data on germplasm was collected. Locations may be very small precise sites such as fields or plots or quite large places like countries or even regions.
A distinction is made between (a) locations named for administrative or political reasons unrelated to germplasm, such as towns, provinces and countries, and (b) locations that have been used in a particular way for germplasm, such as locations where germplasm trials have been conducted or germplasm has been collected. ICIS provides for hierarchical classification of locations by country and three sub-national administrative levels. This classification may be used to help identify the administrative setting of locations used for germplasm.
A distinction is also made between location information and environmental data. Location concerns geographic position and relationships and does not concern environmental characterization such as climate and soil chemistry and land use. Such data are stored in DMS or specialist databases, not in the location management system.
ICIS stores location information in a set of tables duplicated in the central and local databases. This information is managed by the Location Management Module (LMM) described in Chapter 9. One aspect of this management is unique identification of locations, which is handled in exactly the same way as for germplasm (2.4) with local location IDs and descriptor types being negative until they are updated to the central database when unique positive identifiers are assigned.
Primary Location Information
The primary objectives for storing location data are to describe locations with sufficient precision to permit a researcher, with no additional knowledge, to relocate a specified location and to link the location to spatially referenced data such as soil maps or climate databases. The primary information stored in the location table is therefore a location name, and the primary hierarchy of country, province, district, and municipality. The last three sub-divisions are not uniquely defined for all countries and so are referred to as first, second and third sub-national divisions in order to be more generic.
The LOCATION Table
| Columns - Long Name (Name) | Description | Type | Length (bytes) |
|---|---|---|---|
| LOCATION_ID (LOCID) | The unique identifier of the location. | Long | 4 |
| LOCATION_TYPE (LTYPE) | Specifies the type of location. This may be an administrative or political category (e.g., Country, Province, District, Town, etc) or some other category related to the use of the location for germplasm (e.g. nursery test site or germplasm collection site). Links to types defined in the UDFLDS table.
For locations used for germplasm, sometimes the only information available may be admin/political information. For example, a germplasm sample may have been collected from somewhere in the province of Palawan in the Philippines, and no other information is available on the collecting location. In this case, two location records are required: one for the province named Palawan (with LTYPE= the code specified in UDFLDS for province), and one for the collecting location (with LTYPE=the code specified in UDFLDS for collecting location); and the record for the collecting location would have SNL1ID= the LOCID of the record for the province. | Integer | 2 |
| NO_LATLONG (NLLP) | Number of LAT-LONG points in the polygon describing the Location. Zero if no LAT-LONG | Integer | 2 |
| PREF_LOC_NAME (LNAME) | Preferred name of the location.
To enable data validation, names of administrative locations should conform to those used in digital gazetteers. No standard naming conventions are available for locations used for germplasm. A location may be assigned a coded ID (such as BUR010), or it may have a text description (such as 2km E of Los Baños), or it may not be named at all. There is no requirement to assign a name to an unnamed location: it may be precisely identified by its latitude-longitude coordinates (in table GEOREF), or it may be loosely defined (through SNL1ID, SNL2ID or SNL1ID) by the administrative location in which it occurs. In particular, the name of the containing administrative region should not normally be replicated to the record used for a location of a germplasm location. In the example above where a germplasm sample was collected from Palawan in the Philippines, the location record describing the collecting location would have no name; and the province name would be obtained by looking up the LNAME of the LOCID pointed to by SNL1ID. | Character | 60 |
| ABBREV_LOC_NAME (LABBR) | Preferred abbreviated name of the location | Character | 8 |
| SUBNAT _LEVEL3 (SNL3ID) | Name of third level of political subdivision within country (e.g. Township or Vereda). | Long | 4 |
| SUBNAT _LEVEL2 (SNL2ID) | Name of second level of political subdivision within country (e.g. Municipality or County). | Long | 4 |
| SUBNAT _LEVEL1 (SNL1ID) | Name of first level of political subdivision within country (e.g. State, Province Department) | Long | 4 |
| COUNTRY_CODE (CNTRYID) | Country code linked to COUNTRY lookup table | Long | 4 |
| LOCATION_REPLACE (LRPLCE) | Own LOCID for deletion, replacement LOCID for replaced records, zero otherwise | Long | 4 |
Secondary Location Information
Additional information about locations is stored in user defined descriptors which are defined in the USER DEFINED FIELDS (UDFLDS) table (3.6.1). Care should be taken to ensure that only descriptors relating to location are stored. This requires attention to the distinction between location and environmental data made earlier. Values of descriptors are stored in the LOCATION DESCRIPTOR TABLE. One example of a location descriptor might be a description of a route to the location with reference to more readily located sites.
The LOCATION DESCRIPTOR TABLE (LOCDES)
| Columns - Long Name (Name) | Description | Type | Length (bytes) |
|---|---|---|---|
| LOCDES_ID (LDID) | Identifier for location descriptor | Long | 4 |
| LOCATION_ID (LOCID) | Identifier for the location | Long | 4 |
| DESCRIPTOR_TYPE (DTYPE) | Descriptor type, links to the UDFLDS table | Integer | 2 |
| USER_ID (DUID) | Identifies the ICIS user who entered the value. | Integer | 2 |
| DESCRIPTOR_VALUE (DVAL) | Specific value assigned by a user to the location. | Text | 255 |
| DESCRIPTOR_DATE (DDATE) | Date the value was assigned. | Long | 4 |
| DESCRIPTOR_REF (DREF) | Reference for descriptor source, links to BIBREFS table | Long | 4 |
Georeferencing Locations
The best way to specify locations is through geo-referenced polygons, but this is not always feasible. Providing an accurate definition of a location as the clockwise polygon joining a number of lat-lon points (NLLP) provides the possibility of linking to GIS software. In most cases a single lat-lon point (NLLP=1) is given.
Description of the GEOREFERENCE (GEOREF) Table
| Columns - Long Name (Name) | Description | Type | Length (bytes) |
|---|---|---|---|
| LOCATION_ID (LOCID) | Identifies the location. Link to the LOCATIONS table. | Long | 4 |
| LATLON_POINT_NUMBER (LLPN) | The lat-lon point (1 to NLLP). | Integer | 2 |
| LATITUDE (LAT) | Latitude in decimal degrees (+ for North, - for South, -1E36 for missing). | Real | 8 |
| LONGITUDE (LON) | Longitude in decimal degrees (+ for East, - for West, -1E36 for missing). | Real | 8 |
| ALTITUDE (ALT) | Altitude (m above sea level, -1E36 for missing) | Real | 4 |
