GeoCSV: Unterschied zwischen den Versionen

Version vom 1. Mai 2015, 13:22 Uhr

Specification of the tabular file format CSV (Comma Separated Values) with a geometry extension!

CSV file format specification

About the content:

• First row contains attribute names separated by a => delimiter.
• Following rows are contains values separated by a => delimiter.
• Delimiter is semicolon (;) by default.
• Strings are enclosed by parantheses, to allow delimiters inside (e.g. "string").
• Data types (if supported from source or target system): See CSVT file format specification.
• All rows have same number of attributes.
• Calculations are possible in fields of type String (like "=A1+B1")

About file extensions, encoding and compression:

• Proposed file extension is .CSV (or .csv).
• Compression in format .ZIP (or .zip) is also possible and encouraged.
• Encoding is UTF-8 by default.
• End-of-lines are: CR, LF or CR/LF.
• Line Breaks in (String) fields are disallowed.

GeoCSV file format specification

GeoCSV is based on CSV. The extension comes with two variants: Options easting/northing and Options WKT.

Option "easting/northing" (longitude/latitude, similar to x/y in mathematics):

• Geometry Point type as two neighboring columns of type Float: one containing the easting coordinate, and one containing northing coordinate separated by the common delimiter.
• Example for the two easting/northing columnts "8.8249;47.2274".
• This option supports only Points.

Option WKT:

• It' one single column of type String containing a constructor, like for example: "POINT (8.8249 47.2274)".
• This option supports Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon.
• WKT ("Well Known Text") is originally defined by the Open Geospatial Consortium (OGC) and described in their Simple Feature Access specification (also ISO SQL/MM). See e.g. http://en.wikipedia.org/wiki/Well-known_text

Common restrictions:

• Coordinate system is WGS84 (EPSG:4326) by default.
• There is only one geometry column allowed per sheet.
• All geometry values within one table are in the same coordinate reference system (CRS).

CSVT file format specification

Field/column types, case insensitive (if supported from source or target system):

• Integer
• Real
• String
• Date ("YYYY-MM-DD"), Time ("HH:MM:SS+nn") and DateTime (YYYY-MM-DD HH:MM:SS+nn)
• (Lon/Lat)
• (WKT)

Notes:

• The geometry types are a kind of subtype: easting and northing values are stored as float, option WKT is stored in one column of type String.
• See also http://www.gdal.org/drv_csv.html section with .csvt extension.

Software

• Desktop
  • LibreOffice / OpenOffice
  • Excel
  • OGR
  • QGIS
• Online:
  • GeoConverter
  • CSV-to-GeoJSON: convertcsv.com, csv2geojson
  • GeoJSON-to-CSV: convertcsv.com

Examples

CSV type file 'example1.csvt':

Integer;String,Real,String,WKT

CSV file 'example1.csv:

id;name;amount;remarks;geom
1;Kevin;2.1;Rapperswil;point(8.8249 47.2274)
2;Eva;2.2;Zürich;point(8.5435 47.3768)
3;"Jimmy;Muff";2.3;Berne;point(7.4397 46.9487)

...can be shown as following table:

Note the remarks string in row 2 and the empty string in row 3.