So how do you construct and maintain a national basemap?

December 9, 2013 Gordon Plunkett

Natural Resources Canada's Mapping Information Branch recently received a prestigious award for completing the initial mapping of all of Canada at 1:50,000 scale, but another big job still lies ahead of them.

The Mapping Information Branch of Natural Resources Canada (NRCan) was recently awarded the Royal Canadian Geographical Society’s (RCGS) Gold Medal for the completion of the topographic mapping of Canada at the 1:50,000 scale. The RCGS reported that the completion of this mapping represents a major milestone in the history of cartography in Canada. They went on to indicate that the rapid mapping of over 1,600 topographic maps in the last three years marks the culmination of a century of mapmaking. As of today, the whole of the Canadian landmass has been mapped at least once at the 1:50,000 scale.

This is, in fact, a major milestone for Canadians. Hardcopy paper maps are still in use today for a variety of purposes. With Canada being the second largest country in the world by area, NRCan's production of over 10,000 different topographic maps for a country the size of Canada is an enormous piece of work. Congratulations to NRCan on this exceptional achievement and prestigious award.

Figure 1: Natural Resources Canada has won a prestigious award for mapping Canada. From left to right: Paul Ruest (RCGS), Yvan Désy & Sylvain Lemay (NRCan) and Governor General David Johnston

While the usefulness of hardcopy maps today is not in question, there's also a significant broader use for the information contained on these maps within the growing digital community. GIS can make use of this foundation data as a base for presenting information pertaining to situational awareness, community planning, environmental monitoring, demographic analysis plus many other applications that require study over large areas.

Before GIS, individual hardcopy maps were a convenient way to store, retrieve and use geographic information. However, because of the large storage capacities of GIS, the artificial splitting of the country into numerous map sheet areas is no longer required. Stitching these maps together is what's termed as creating seamless coverage, and NRCan is now working on this task.

However, at NRCan, this poses a problem because these thousands of maps were created over many decades and the technology, standards and quality have changed significantly over that period. Thus, it's not possible to just copy the individual digital map files into a GIS database as there will be significant differences between adjoining maps. For example, Canada changed from the imperial measurement system to the metric system, so some maps are still imperial-based while newer ones are metric-based.

Also, there's the task of aligning features at the map boundaries, which is often called edge matching. This issue occurs in the border areas of adjacent maps where some map objects, which cross the map edge, will likely not perfectly match or align. These objects include contour lines, roads, rivers and boundaries, for example. However, these objects all need to be aligned across the map edges (plus the object attributes need to be adjusted) in order to create a seamless national coverage.

Over and above the technical issues of creating a seamless national basemap, the major problem now is how does NRCan keep this data up to date? How can this map data be updated, now that the entire country has been mapped at the 1:50,000 scale at least once?

Winning the Royal Canadian Geographical Society 2013 Gold Award is quite an accomplishment for NRCan, but perhaps the work of keeping this national treasure of map data up to date is going to be the real test.

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About the Author

Gordon Plunkett

Gordon Plunkett is the Spatial Data Infrastructure (SDI) Director at Esri Canada. He has more than 30 years of experience in GIS and Remote Sensing in both the public and private sectors. He currently sits as a member of the Community Map of Canada Steering Committee, GeoAlliance Canada Interim Board of Directors, the Open Geospatial Consortium (OGC) Technical Committee, the Canadian General Standards Board (CGSB) Committee on Geomatics, the University of Laval Convergence Network Advisory Committee and the Advisory Board to the Carleton University Geomatics and Cartographic Research Centre. During his career, Gordon has worked on projects in more than 20 countries and has contributed to numerous scientific conferences and publications. At Esri Canada, he is responsible for developing and supporting the company’s SDI vision, initiatives and outreach, including producing content for the SDI blog.

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