Shapefile is a common GIS format developed for vector datasets that should work with most GIS applications.
Files within each Shapefile download
Your Shapefile download will contain a range of different file formats, which each do a different kind of work within your application. These may include:
- .shp: this file represents the feature geometry - i.e. the points, lines and polygons in spatial dataset.
- .shx: this file represents the ‘shape index position,’ and is used to search forward and backwards.
- .dbf: this is the database file, which contains attribute data and object IDs.
- .prj: this file will contain the projection information.
- .cpg: this identifies the character encoding for the .dbf database file.
Attribute names for Shapefile exports
Because attributes are held within the DB4 file format, .dfp, attribute names for Shapefiles can only be 10 characters long. For exports of datasets with longer attribute headers, Koordinates assigns a unique attribute name at the moment of import.
Note also that Shapefiles cannot store null values, and cannot store both a data and a time in a single field.
Text attribute limits
Text attributes for Shapefile data are limited to 254 characters. When you export a layer to Shapefile that has text attributes of longer than 254 characters, we truncate any affected fields, which means that will you lose some information.
Download limits for Shapefiles
Download limits for Shapefile are determined by the limits of two of its constituent file formats:
- .dbf has a download limit of 2GB.
- .shp and .shx has a download limit of 2GB.
When a user's export exceeds 2GB, we split the file into clusters. These clusters are pre-assigned when data is imported to the platform, and are split along the primary axis of the data layer. This means that your export may be split into multiple smaller shapefiles, depending on how many of these pre-assigned clusters are crossed by your chosen extent.
Esri's spatial index
For performance reasons, Koordinates does not support Esri's spatial index for either import or export.
Projections for Shapefile exports are stored in a .prj file. Projections are in EPSG, which is an international database of projections that assigns a unique number to a range of projections. The EPSG number within the .prj file will be recognised by many GIS software applications, which will accordingly know the projection in which to display the data.
For data imports, Koordinates requires publishers to provide an EPSG.
As noted above, Shapefile is a geospatial vector format. However, if there are tables in your collection, it will be exported as .dbf - the database file that contains attribute data and object IDs for Shapefiles.