Why should we collect geospatial data just once?
For some time, many SDI strategies, plans and visions for geomatics have contained the following catchy phrase about data: “collect once and use many times”. While this aphorism has served the geomatics community well in the past, it gives the wrong impression about data maintenance. The phrase implies that geospatial data needs to be collected only once and never again. In fact, most data needs to be refreshed on a specific schedule because the real world is continually changing over time and the data needs to be recollected to reflect these changes. So how can we reword this catch phrase?
The Canadian Geomatics Accord, which was signed by many federal and provincial agency heads in 2007 related to geospatial data sharing, states as a principle of operation: ”Data should be collected only once, closest to the source and in the most efficient way possible.” As a second principle of operation it states: “Data should be integrated both horizontally and vertically across jurisdictions, to reduce duplication of efforts and to promote the concept of collect data once, use many times.” This accord expired in 2012 and is currently being renewed.
The first common principle of the European INSPIRE SDI states: “Data should be collected only once and kept where it can be maintained most effectively.” In an economic benefits document, Land Information New Zealand states: “This can be achieved through using a spatial data infrastructure to ‘collect once, use many times’.” The UK Location Programme states: “Data should be collected only once and then re-used, subject to re-use of public sector information regulations.” The United Nations Initiative on Global Geospatial Information Management indicates: “The principle of 'collect once - use for multiple tasks’ demands collaboration.”
While most geomatics experts and practitioners in Canada and around the world would understand what is meant here, non-geomatics managers and executives (who are often making decisions regarding programs and funding) do not understand the nuance. I’ve even heard the following statement: “Well you have collected the data once, why do you need to collect it again?” Clearly the wrong message is being sent with the wording “collect once”.
The Esri Canada Community Map is a zoomable Web map with nearly 20 different map scales. Some of the data for the same geographic location was collected by different organizations at different times and at different scales. Is this really “collect once”? Remote sensing imagery is often collected according to the orbital pattern of the satellite at many different times, but at the same location. So this means that the satellite is not collecting the data only once.
Figure 1: Geospatial data collected for the same location at different times
The aphorism “collect once” unfortunately does not mean that the data is collected only once ever. It means that the data is collected at a particular time once and usually under the guidance of a single organization. In practice, data for the same location may be collected again and again according to a data revision cycle or the scale of the data collection.
So what’s the solution to this catchphrase confusion - this declaration dilemma? One can’t say “collect the data forever” as this also sends the wrong message. How about “collect as needed” or “collect on a schedule”, but neither of these are catchy phrases like “collect once.”
What’s clear is that the wording needs to be changed. What’s not clear is what it should be changed to. In the past, geomatics was the realm of the geomatics professional who understood the phrase. Today, geospatial data has broad based usage and is sometimes managed by individuals who are not and who need not be geomatics experts. What’s important now is that any new wording we choose for public messaging about SDIs be not only catchy and concise but also clear.
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