Scientists
Research Grants
Scientific Publications
Informatics Research
NSIDC Scientific Expeditions
Scientists blog from Antarctica and provide a glimpse of what it's like to do research in the field. 
What's hot in the news around climate and sea ice and what are scientists talking about now? 
The Canadian Ice Service (CIS) produces digital Arctic regional sea ice charts for marine navigation, climate research, and input to the Global Digital Sea Ice Data Bank (GDSIDB). The ice charts are created through the manual analysis of in situ, satellite, and aerial reconnaissance data. The ice charts have information on ice concentration, stage of development, and ice form, following World Meteorological Organization terminology. These sea ice charts begin in 2006 and cover the following regions of the Canadian Arctic: Northern Canadian waters (Western Arctic, Eastern Arctic, and Hudson Bay) and Southern Canadian waters (Great Lakes and East Coast). Each regional shapefile (.shp) (encoded in SIGRID-3 format) and associated metadata file (.xml) are combined into a tar archive file (.tar) for distribution. All data are available via FTP.
Canadian Ice Service Arctic Regional Sea Ice Charts in SIGRID-3 Format, Version 1
This is the most recent version of these data.
|
Geographic Coverage |
FTP data can be downloaded through a Web browser or command line via FTP. For help downloading data through an FTP client, go to the How to access data using an FTP client support page.
As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.
Canadian Ice Service, . 2009. Canadian Ice Service Arctic Regional Sea Ice Charts in SIGRID-3 Format, Version 1. [Indicate subset used]. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: https://doi.org/10.7265/N51V5BW9. [Date Accessed].The Canadian Ice Service (CIS) is an operational data provider with a primary objective of serving the operational user community. This support results in part in the production of regional ice charts over the Canadian Arctic. The Manual of Standard Procedures for Observing and Reporting Ice Conditions (MANICE) is the authoritative guide produced by the CIS that explains how sea ice charts are produced (Environment Canada 2005).
Detailed Data Description
These data are available in SIGRID-3 format. The SIGRID-3 format includes several files: a shape file (.shp), with associated files (.dbf, .prj, .shx), and a metadata file (.xml). Each set of files is combined into a tar file (.tar) for distribution.
The CIS followed the SIGRID-3 (IOC 2004) instructions for decoding sea ice, but made a few modifications to the SIGRID-3 metadata files (.xml). Review CIS 2006 for a complete description of the differences between the CIS SIGRID-3 format and the official SIGRID-3 format (IOC 2004). These deviations from the CIS SIGRID-3 metadata format (noted almost verbatim from CIS 2006) are listed below:
- The Canadian Ice Service chose to exclude the style sheet reference to the
FGDC_V2.xslfrom the XML due to the possible problems, such as availability and updates, that can be encountered when referencing to off site information. - The
Time_Period_of_Contentis described using the Single Date/Time option since it better represents the valid date and time of the CIS scheduled products. - The CIS
Contact_Addresssection includes the Address and Country elements since they are required at CIS for mailing purposes. - The CIS included
Contact_FacsimileandContact_Electronic_Mail_Addresselements to offer more contacting options to their clients, since this is the only section in the metadata where contact information is found. - Their
Spatial_reference_Informationrefers to Geographic not Polar Stereographic along with its mandatory information as agreed at the last International Ice Charting Working Group meeting in Ottawa. - The CIS included and defined the
COVSHP_and theCOVSHP_IDattribute labels after the Perimeter label, since they are automatically inserted when converting from coverage to shapefile using the ESRI application.
(CIS 2006)
There were also modifications made at the CIS to the coastlines as noted in CIS 2006:
SIGRID-3 files issued from CIS contain coastline vector features which are derived from the Digital Chart of the World (DCW) data set of 1993. The DCW was originally created by the Environmental Systems Research Institute (ESRI) at the request of the US Defense Mapping Agency (DMA) using aeronautical charts at a 1:1,000,000 scale as the primary data source.
CIS introduced a new coastline for the winter of 2008. This was a modified version of the 1:1,000,000 scale data set from World Vector Shoreline Plus (WVS+), 3rd Edition, 2004. WVS+ is a digital database product consisting of country, coastline, and ocean coverage for the entire world. WVS+ was produced by the National Geospatial-Intelligence Agency (NGA), formerly the National Imagery and Mapping Agency (NIMA). The coastline data used in WVS+ was developed using coastal nautical charts produced by the DMA.
The DCW and the WVS+ data set contains vector data which has been customized at CIS to correct gross errors, particularly in the Canadian Arctic and Greenland.
These modified coastlines for North America are incorporated into data products generated by CIS. The underlying reference frame for the data is the World Geodetic System of 1984 (WGS84) using the updated WGS Earth ellipsoid (2004) (CIS 2006).
SIGRID-3 Defined
Egg code that depicts ice in an area by total concentration, partial concentration, stage of development, and form of ice. Image courtesy of Environment Canada. Used with permission.
Originally, operational data centers denoted ice characteristics by grouping the ice with similar characteristics into polygons. Within each area or polygon, ice was identified by an egg code. The egg code, termed this way because of its shape, was a way to map the ice characteristics such as total ice concentration, partial concentrations, stage of development, and form of ice on a paper map. Figure 1 shows the ice categories included in the egg code. This method worked well, but then the digital era emerged and operational centers shifted their focus from paper charts to digital ice charts and used GIS techniques to process data and produce ice charts. With this digital transformation came a shift from the paper egg codes to a digital representation of sea ice conditions.
The operational data centers needed a way to incorporate the information from the paper charts to a digital format. In the 1980s, a Sea Ice Grid (SIGRID) format was developed (Thomson 1981) and adopted as a World Meteorological Organization (WMO) standard shortly thereafter. This format has evolved over time with the latest version, which is now a vector format, called SIGRID-3 (IOC 2004). For a more complete history of the egg code and ice chart digitization, including a summary of the SIGRID-3 format, see the History of Ice Chart Digitization section of the National Ice Center Arctic Sea Ice Charts and Climatologies in Gridded Format documentation and the material at the Global Digital Sea Ice Data Bank site.
The SIGRID-3 look-up table converts the ice codes into meaningful sea ice characteristics. For example, in Figure 2, the Total Ice Concentration (CT) value of 80 translates to a CT of 8/10 (IOC 2004).
This example shows how the egg code parameters (CT, CA, CB) in Figure 1 are mapped to individual SIGRID-3 codes. Before 30 May 2018, the data files contained two extra columns called COVSHP and COVSHP_ID. These columns were not required to read the data, so they were removed from the data files beginning 30 May 2018.
Tar files range in size from 340 KB to 4.2 MB.
The data files in this data set are available via FTP. The top level of the directory structure, G02171, is divided into five main directories (one for each region of this data set): East_Coast, Eastern_Arctic, Great_Lakes, Hudson_Bay, and Western_Arctic. Refer to Figure 4. Each region directory is further broken down by the four-digit year. Refer to Figure 5. Within each year is the tar file that contains the shapefile and the associated metadata file.
Tar file
The tar files are named according to the following convention and as described in Table 1:
cis_SGRDRXX_YYYYMMDD_pl_v.tar
Within each tar (.tar) file, there are four files that constitute a shapefile (.shp, .shx, .dbf, and .prj) and an associated metadata file (.xml).
Shapefile and Metadata File
The shapefiles and their associated metadata files are named according to the following convention and as described in Table 2:
cis_SGRDRXX_YYYYMMDD_pl_v.xxx
Where:
| Variable | Description |
|---|---|
| cis | Denotes that this file is from the Canadian Ice Service |
| SGRD | SIGRID-3 format |
| RXX | Region name abbreviation GL: Great Lakes EC: East Coast WA: Western Arctic EA: Eastern Arctic HB: Hudson Bay) |
| YYYY | 4-digit year |
| MM | 2-digit month |
| DD | 2-digit day |
| pl | Feature type (pl: polygon) |
| v | Version number. Permits multiple charts per day a: 1st version b: 2nd version and so forth |
| .xxx | File extension (.shp, .shx, .dbf, .prj, and .xml) |
Note: In some cases, the original files needed to be replaced with newer files. These newer files have the following file naming convention:cis_SGRDREA_YYYYMMDD_pl_v_YYYYMMDDTTTTTT.tar The later variables (YYYYMMDDTTTTTT) contain a timestamp. The time stamp is GMT and corresponds to the time that the file was created.
The parameters include total ice concentration, partial concentration, stage of development, and ice form. Sea ice thickness can be assessed using stage of development as a proxy for thickness (NIC 2006).
Sample Data Record
This section contains some sample data records including a sample of two SIGRID-3 shapefiles: One for the Great Lakes Region (Figure 6) and one for the Hudson Bay Region (Figure 7). Further, the beginning portion of a metadata file is also displayed (Figure 8).
The symbology was modified to correspond to some images in the National Ice Center Climatology data set. The results show the varying ice concentration around the Great Lakes.
The symbology was modified to correspond to some images in the National Ice Center Climatology data set. The results show the varying ice concentration in the Hudson Bay.
Each shapefile contains an associated metadata file. The metadata files for the various regions are very similar. They differ only on these specific metadata fields: <bounding> (coordinates), <pubdate>, <title>, and <caldate>. Here is the beginning portion of metadata from cis_SGRDRHB_20080324_pl_a.xml that corresponds to Figure 2.
This data set covers the Canadian Arctic regions including Northern Canadian waters (Western Arctic, Eastern Arctic, and Hudson Bay) and Southern Canadian waters (Great Lakes and East Coast). Figure 3 displays these regions.
Note: The specific geographic coordinates for each region are listed in the metadata associated with that region.
This map shows the spatial coverage of the Canadian Arctic regions for both the Northern Canadian waters and the Southern Canadian waters. Image courtesy of the Canadian Ice Service.
Because this data set is provided as vector shapefiles, there is no inherent resolution.
Projection
NSIDC adds a projection (.prj) file to each tar file received from CIS. NSIDC renames the projection file to correspond to the shapefile file name in each tar file. For example: cis_SGRDRHB_20061211_pl_a.shp and cis_SGRDRHB_20061211_pl_a.prj.
Shapefiles from 01 March 2006 through 24 July 2011 use the following projection in the projection file (.prj):
GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0], UNIT["Degree",0.0174532925199433]]
Shapefiles after 24 July 2011, use the following projection in the projection file (.prj):
PROJCS["WGS_1984_Lambert_Conformal_Conic",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]], PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["False_Easting",0.0], PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-100.0],PARAMETER["Standard_Parallel_1",49.0], PARAMETER["Standard_Parallel_2",77.0],PARAMETER["Latitude_Of_Origin",40.0],UNIT["Meter",1.0]]
Temporal coverage spans from 2006 to the present. The start date of the data for each region differs. See Table 1 for a list of start dates by region. Data begin in 2006 when production of the ice charts in SIGRID-3 format began. Users should note that the CIS has produced regional ice charts since 1968 in .e00 format, but these files are not included in this SIGRID-3 data set.
| Region | Start Date of Data |
|---|---|
| Western Arctic | May 2006 |
| Eastern Arctic | June 2006 |
| Hudson Bay | May 2006 |
| Great Lakes | Dec 2006 |
| East Coast | May 2006 |
The temporal resolution is as follows:
- Northern Canadian waters: Weekly (summer) and bi-weekly (winter)
- Southern Canadian waters: Weekly (winter); files are not produced in the summer
Each ice chart contains up to 72 hours of input data. For example, a chart dated 16 October 2006 may contain data from the previous three days, as noted in each metadata file.
Software and Tools
The shapefiles can be read using GIS software and the tar files can be opened using tar extraction software.
Data Acquisition and Processing
Data Processing
The CIS uses the operational Ice Service Integrated System (ISIS) to create the regional ice charts based on MANICE procedures (Environment Canada 2005). The CIS takes input from various sources such as satellites, aerial reconnaissance, and ship reports based on data availability. They create coverages and then convert the coverages to shapefiles with corresponding metadata. Each metadata (.xml) file lists the sources used. Users should note that this list of sources is comprehensive and lists all possible data sources, not just the data sources that directly relate to that shapefile.
Error Sources
Not all potential sources of error have been identified. Users can look at MANICE (Environment Canada 2005) for more information. There are potential errors introduced with the manual assimilation process. See the section on Other Related Data Collections and References and Related Publications for more information.
Quality Assessment
A full quality assessment of this data set was not completed. However, the metadata files state the following:
"The reliability and accuracy of the data set is directly related to the availability, resolution and the effects of atmospheric (cloud, daylight, etc.) and ground (snow, rain, sea state, etc.) conditions on the source information. The source information is incorporated in the Regional Ice Analysis if the source information publication or acquisition date is plus or minus three days of the Regional Ice Analysis publication date. The only exception is the Regional Ice Analysis source information where we use the previous publication date".
References and Related Publications
Contacts and Acknowledgments
Dan Fequet
Canadian Ice Service
Environment Canada
373 Sussex Drive, Block E
Ottawa, Ontario K1A0H3
We thank Richard Chagnon and Dan Fequet from the Canadian Ice Service for providing this data set to NSIDC.
Distribution of the data set from NSIDC is supported by funding from NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) and the National Geophysical Data Center (NGDC).
Document Information
Document Authors
L. Ballagh prepared this document based on SIGRID-3 guidelines (IOC 2004), CIS SIGRID-3 implementation (CIS 2006), the metadata files, and on correspondence with R. Chagnon and F. Fetterer. Document edited by A. Windnagel.
Document Creation Date
October 2009
Document Revision Date
May 2018: A. Windnagel updated Figure 2 to describe the change in format for data starting 30 May 2018.
January 2011: A. Windnagel implented changes requested by Dan Fequet.
July 2010: A. Windnagel added a paper to the related publications section.
NSIDC User Services
Phone: 1 303 492-6199
Email: nsidc@nsidc.org
