Creating a User-Defined Centrus Spatial Database

To create a user-defined Centrus spatial database, choose a format that is supported by the module you want to use to perform a spatial analysis. The following formats are supported by one or more Spectrum™ Technology Platform modules. See User-Defined Centrus Databases for a listing of the specific formats that each module supports.

ESRI Shapefile

An ESRI shapefile (.SHP) can contain points, lines, and polygons. For more information on the shapefile format, see:

http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf

MapInfo MIF/MID

The MIF/MID format is comprised of two files, one with an extension of MIF, the other with the same name, but the extension MID. The MapInfo Interchange Format (MIF) file contains the actual points that represent the objects, while the MID file contains the text information about the objects. For a complete description of the format, see:

http://resource.mapinfo.com/static/files/document/1074660800077/interchange_file.pdf

MIF files contain a tokenized header, followed by a DATA section. The comma delimiter is required. If a DELIMITER token is present in the file, the file is not imported.

The next part of the file header contains the definitions of the columns in the MIF file. Feature names, as well as numeric data about the features, are stored here. One of these columns is used as the identifier to store with the object.

The column definitions begin with the COLUMN token, followed by the number of columns in the MIF file. Following the COLUMN token is a single line entry for each column. The first entry on the line is the column name, the second is the column type. The following example indicates three columns in the MIF file:

COLUMN 3 FEAT_NAME char (15) POPULATION integer AREA decimal (8,4)

Any column type can be used as the name, but char is the most common, since that represents a string. The number in parentheses following char indicates the largest string (which cannot exceed 127 characters). For a complete listing of column types, contact MapInfo.

The token DATA indicates that the header is complete, and the listing of objects follows. For each object, a number of attributes may be listed, such as PEN and BRUSH. These settings are ignored. MapInfo supports a variety of object types, though only a few are used to represent geographical objects. Three object types are supported—Region, Polyline, and Point.

In a MIF file, latitude/longitude coordinates must be represented in decimal degrees, with up to six decimals of precision. Longitude is the x coordinate, and latitude is the y coordinate. Western longitudes and southern latitudes are always negated. This means that for the U.S., longitudes are negated, while latitudes are positive. User coordinates are entered as whole numbers, as the decimal portion is ignored.

Region Definition

A region consists of one or more polygons. Each polygon is uniquely defined. In a MIF/MID file, you do not need to "close" a polygon. The last point in the polygon automatically attaches to the first point in a polygon with a line segment. The format for a region object is as follows:

REGION #pgons numpts1 x1 y1 x2 y2 . . numpts2 x1 y1 x2 y2 . .

Polyline Definition

A polyline (PLINE) is a line that contains any number of points to define its shape. The number of points in the line follows the PLINE identifier. Below is the format for a PLINE object.

PLINE numpts x1 y1 x2 y2 . .

Point Definition

A point is defined as a single coordinate pair. Below is the format for a point object.

POINT x y

MID files list the data, such as name, for objects defined in the MIF file. There is one entry in the MID file for each object in the MIF file. The entry in the MID file must be in the same order as the objects appear in the MIF file. The data in the MID file is delimited by commas, unless otherwise configured by the DELIMITER statement in the MIF file. The comma is the only supported delimiter.

As an example, recall the column definitions used earlier in the MIF file:

COLUMN 3 FEAT_NAME char (15) POPULATION integer AREA decimal (8,4)

With this column definition, and assuming comma delimiters, sample entries in the MID file appear as:

First Feature,180232,1000.2345 California,4345105,56023.3569 Last Feature,12643,136.4000

Note: Columns are separated by a single comma. There is no header or other information contained in the MIF file.

MapInfo TAB

The MapInfo .TAB file format is used by MapInfo Professional. For more information, see the MapInfo Professional User Guide.

DBF

The DBF format is a common database format. Spectrum™ Technology Platform only supports point data in DBF format. If you want to create a user-defined spatial file of lines or polygons, you must use the shapefile format.

The DBF file must contain longitude and latitude fields using the following names:

Note: The field types must be Character, Date, Numeric, or Float.

Microsoft Access Database

Database files created with Microsoft Access can be used with Spectrum™ Technology Platform if they can contain point data only. User-defined spatial file of lines or polygons must use the shapefile format.

The .MDB file must contain fields using the following names:

The file may also include other fields. Field names must not be longer than 10 characters.

Note: The field types must be Character, Date, Numeric, or Float.

Text/CSV

Text files (.TXT) and comma-delimited files (.CSV) can contain points only, not polygons. If you want to create a user-defined spatial file of lines or polygons, you must use the shapefile format.

The file may also include other fields. Field names must not be longer than 10 characters.