BC Environment Standard Projection

BC Environment GIS Working Group has chosen a standard projection and datum for all spatial data stored in ARC/INFO.

The projection is Albers Equal Area Conic, with parameters of :

The datum is NAD83, based on the GRS80 ellipsoid.


ARC/INFO data stored in geographics (ie coordinates are in Longitude/Latitude) may need extra processing when converting Long/Lat to Albers.


This tutorial explains some of the issues involved in choosing a map projection, and characteristics of the commonly-used ones.

Projection choice

The Albers Equal Area Conic projection was chosen because :

Parameter choice

Datum choice

The NAD83 datum is preferable to NAD27 in British Columbia, and is also used as the base for Terrain Resources Inventory Mapping (TRIM) by Surveys and Resource Mapping Branch of BC Lands. As NAD27 data is added to the corporate spatial database, it is NAD-shifted to NAD83 using the Canadian National Transformation Matrix.

Contact person

If you have any questions, comments, or concerns on this subject, please contact the GIS Technical Analyst.


A subcommittee of the GIS Working Group was formed to decide on a standard projection. Its findings are summarized below.


Snyder, and the ARC/INFO 'User's Guide to Map Projections and Coordinate Management' were used.

Other agencies

A survey of other provincial ministries and agencies found no clear standard.

ARC/INFO limitations

Most of ARC/INFO's analysis functions (eg UNION, the polygon overlay function) do not work across map projections (ie both layers must be stored in the same projection). This made it important that one projection plane be used for all provincial data.

Projection choices

The projections considered and rejected were:

Projection testing

Both Lambert Conformal Conic (two parallels), and Albers Equal Area were tested statistically for distortion of area and distance.

A polygon coverage of the entire province was created, composed of rectangular areas (The 1:20,000 BCGS mapsheet neatlines) in longitude/latitude. This coverage was projected into UTM, Lambert, Polyconic, and Albers. The areas, latitudinal (horizontal) widths, and longitudinal (vertical) heights of the polygons in each projection were calculated. These measurements in each of the three projections were then compared with the corresponding measurements in UTM.

These tables show:

These images illustrate : As the tables and images show, the representation of both area and distance in Albers is much closer to UTM than either Polyconic or Lambert are to UTM.

Shape distortion

The Queen Charlotte Islands and Haines Triangle were plotted at similar scale in both UTM and Albers. The Albers conic projection rotates the data, because it is so far from the central meridian. However, there are no visible differences in the shapes of the features.