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The many stories in a map – V2.0

About 18 years ago I wrote an article with a similar title – minus the “version 2.0” (Quarry 8[9]: September 2000). That article described how a geological map could be translated into a map showing potential sources of aggregate.

Over my career I have translated quite a few geological maps into aggregate potential maps. There is a world of difference between how I translated geological maps back in the day (prior to the 2000 article) and the way I translate maps these days.

{{quote-A:R-W:300-Q:"Translating geological map units into aggregate potential requires a wealth of experience, the ability to research the literature to learn about rocks where your experience is limited, and a systematic methodology to put everything together."}}Translating geological maps into aggregate potential maps is no easy task. However, the mechanical process has been made much simpler with the advent of reasonably priced geographic information systems (GIS), powerful personal computers and the availability of high quality digital data.

The first step in any geological map transformation is finding a good geological map to use as the source of data. Back in the day, this involved library searches, visits to book and map stores and calls to organisations such as state geological surveys. Today the web contains digital geological maps for all states in the United States.

The geological data commonly will be combined with other data such as topography, hydrology, state and local boundaries, highways, pit and quarry locations and so forth. If that is the case, the next step is to bring all the information to the same scale and same map projection. Back in the day, this was a big deal. Today all the differences can (almost) be fixed with a click of the computer mouse.

However, the one thing computers do not yet possess is the knowledge required to translate a map unit from geology to aggregate potential. A geological map uses different colours and symbols to communicate important information about the distribution of rocks and unconsolidated materials at and near the Earth’s surface. Each colour (map unit) commonly consists of three or more related rock types or sediment types that can be distinguished from adjacent geological map units.

{{image2-a:r-w:300}}Translating geological map units into aggregate potential requires a wealth of experience, the ability to research the literature to learn about rocks where your experience is limited, and a systematic methodology to put everything together.

When I translate a geological map into an aggregate resource map, I determine what rock types likely comprise the map unit. I then assign a relative potential value to that map unit based on what those rock types are and whether one, two or all rock types have the properties to make a suitable aggregate. I then assign a confidence value to that map unit. Finally, I test my interpretations by comparing my derivative map units with the locations of existing or historic aggregate operations.

Actually, there is much more to translating a geological map into an aggregate potential map than revealed here, and it takes time to make a good translation. Time is money, and there is only so much time that can be spent on the translation process before the cost outweighs the benefits.

The good news is that computers and GIS save the translator a huge amount of time – time that can be spent on the “knowledge” side of the process. The bottom line is that today – taking the same amount of time – we can make aggregate potential maps far superior to those made in the “good old days”.

A lot has changed in two decades. I wonder what v3.0 has in store for us!

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