Digital Initiatives at LAC

Digital Policies, Guidelines and Tools

Library and Archives Canada
Local Digital Format Registry (LDFR)
File Format Guidelines for Preservation and Long-term Access
Version 1.0

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2.9 Content Category: Geospatial

Geospatial data consists of spatially defined geographic data that are analyzed through the use of Geographic Information System (GIS) software, image processing systems, or similar types of modeling software and technology. Geographic and spatial data comes in a variety of formats, some of which can be used in GIS software applications. The most popular formats that are used in the Canadian federal government appear below.

2.9.1 Recommended

2.9.1.1 TC 211 ISO 19115 Geographic Information - Metadata (NAP – Metadata) (North American Profile)⁵¹

Geospatial data is defined as data with implicit or explicit reference to a location relative to the Earth. This standard establishes the information infrastructure to support the discovery and use of geospatial information and to enable information sharing among departments, with other jurisdictions, and with the private sector.

Geospatial data important to social, economic and cultural well-being is produced or used by federal departments, the provinces, territories, and others. This includes mapping products to support activities such as search and rescue, geospatial intelligence, and fire fighting. Standardization is essential in this context. It allows data from one source to be easily used with those from another source to create a richer and more useful product. The Standard on Geospatial Data adopts measures that have been endorsed by federal departments, provincial and territorial governments, as well as by academic and private sector participants in the Canadian Geospatial Data Infrastructure.

This standard will allow departments to share data and maximize utility of existing mapping and related products. Departments will also be able to exploit commercially available tools and software in common use around the world to discover, access and use geospatial data. This will result in significant efficiencies in the sharing and use of public sector mapping products. More broadly, it will support departments' mandated programs and services, allowing them to address and respond to economic, environmental and societal challenges more effectively.

2.9.2 Acceptable for transfer

2.9.2.1 Canadian Council on Geomatics Interchange Format (CCOGIF)

This standard specifies the format for the exchange of digital spatial data among Canadian survey and mapping agencies. CCOGIF provides a national standard that preserves the accuracy and content of the exchanged information, and is machine and language independent.

2.9.2.2 Digital Elevation Model (DEM)

A DEM data file consists of an array of terrain elevation samples for ground positions at regular intervals. It is used to create 3D graphics that display the slope, aspect and terrain profiles of a given area. The USGS DEM standard was recently altered to conform to the SDTS format.

2.9.2.3 Digital Line Graphics – level 3 (DIG-3)

The DLG standard was originally developed by the U.S. Geological Survey (USGS) as a National Mapping Program (NMP) standard for the digital representation of many of the country’s traditional 7.5-minute quadrangle cartographic paper maps. The format was created to define topological (i.e., spatial relationships between the data elements) vector-based line data such as roads, rivers and boundaries.

The DLG format is one of the more efficient and widely recognized data formats used for the distribution of vector data. DLG-3 is gradually being replaced by the Spatial Data Transfer Standard (SDTS) interchange format (see below) in the United States Government.

Preservation: The DLG-3 format will be used as a preservation format only if the geospatial content is provided in this format and is not available in a recommended format.

2.9.2.4 Environmental Systems Research Institute (ESRI) Export Format – (E00)

E00 is an interchange data format that was developed by Environmental Systems Research Institute (ESRI) to enable users to move data into and out of its geographic information system (GIS) software package known as ARC/INFO.

A single E00 file describes a complete ARC/INFO coverage. An E00 file is actually an archive of smaller sub-files. Standard sub-files, which have fixed names and are comprised of a fixed data format that does not change from coverage to coverage. The second includes Info sub-files that contain user-defined attribute information.

Preservation: The E00 format will be used as a preservation format only if the geospatial content is provided in this format and is not available in a recommended format.

2.9.2.5 Environmental Systems Research Institute (ESRI) SHape File Format (SHP)

ESRI introduced the Shapefile to provide GIS users with a simple and effective means to disseminate geospatial information, as an alternative to the E00 export file format.

“While the term "shapefile" is quite common, a "shapefile" is actually a set of several files”⁵². Three individual files are normally mandatory to store the core data that comprises a shapefile. There are a further eight optional files which store primarily index data to improve performance. Each individual file should conform to the MS DOS 8.3 filenaming⁵³ convention (8  character filename prefix, fullstop, 3 character filename suffix such as shapefil.shp) in order to be compatible with past applications that handle shapefiles, though many recent software applications work fine with longer file names. For this same reason, all files should be located in the same folder.

Mandatory files:

• .shp — shape format; the feature geometry itself
• .shx — shape index format; a positional index of the feature geometry to allow seeking forwards and backwards quickly
• .dbf — attribute format; columnar attributes for each shape, in dBase III format

Optional files:

• .prj — projection format; the coordinate system and projection information, a plain text file describing the projection using well-known text⁵⁴ format
• .sbn and .sbx — a spatial index⁵⁵ of the features
• .fbn and .fbx — a spatial index of the features for shapefiles that are read-only
• .ain and .aih — an attribute index of the active fields in a table or a theme's attribute table
• .ixs — a geocoding index for read-write shapefiles
• .mxs — a geocoding index for read-write shapefiles (ODB format)
• .atx — an attribute index for the .dbf file in the form of shapefile.columnname.atx (ArcGIS 8 and later)
• .shp.xml — metadata in XML format
• .cpg — used to specify the code page⁵⁶ (only for .dbf) for identifying the character encoding to be used.

The Shapefile is the de facto standard for geospatial data exchange and desktop GIS applications. The openly published Shapefile format is based upon a non-proprietary geospatial data structure.

Preservation: The SHP format will be used as a preservation format only if the geospatial content is provided in this format and is not available in a recommended format.

2.9.2.6 International Hydrographic Organization (IHO) S-57, Edition 3.1

The S-57: IHO Transfer Standard for Digital Hydrographic Data, Edition 3.1 was officially made available in November 2000. IHO S-57 is a standard that describes a data format for the transfer of digital hydrographic data. The standard is based on the ISO/IEC 8211:1994 specification for a data descriptive file for information exchange.

The interchange standard is a media and content independent standard which allows users to name and describe data fields containing both character and binary data. Data structures in the S-57 format can be encoded in either binary or ASCII. The data structure is a tree with a finite number of levels: each file comprises records, each record fields, each field sub-fields.

Preservation: The S-57 format will be used as a preservation format only if the geospatial content is provided in this format and is not available in a recommended format.

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⁵¹ Please refer to www.tbs-sct.gc.ca/pol/doc-eng.aspx?id=16553 for additional information.

⁵² http://en.wikipedia.org/wiki/Shapefile

⁵³ http://en.wikipedia.org/wiki/8.3_filename

⁵⁴ http://en.wikipedia.org/wiki/Well-known_text

⁵⁵ http://en.wikipedia.org/wiki/Spatial_index

⁵⁶ http://en.wikipedia.org/wiki/Code_page

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