Industry News

XYZ is for Cartesian co-ordinates

Pits and quarries, or anything else, for that matter, can be located on the earth in a number of ways. When selecting a method, it is important to use unique identifiers. Let?s look at two suburban communities and see how we can differentiate them.

Suburb#1 is called Anthem. Suburb#2 is called Anthem.
Suburb#1 was built by a nationally known developer. Suburb #2 was built by the
same developer.
Suburb#1 is located about 24 kilometres north of a major US metropolitan area. Suburb#2 ? Ditto.
Suburb#1 is located at Exit 229 from the major north/south interstate serving the area. Suburb# 2 ? Ditto.
Suburb#1 gets much of its aggregate from a nearby river valley. Suburb#2 – Ditto.
About 80 per cent of the aggregate used by the state in which Suburb#1 is located is sand and gravel; about 20 per cent is crushed stone. Suburb#2 ? Ditto.

The annual per capita consumption of aggregate in the state in which Suburb#1 is located is about 6.5 tonnes. Suburb#2 ? Ditto.

These identifiers are not helping distinguish the two suburbs. Fortunately, there are more precise techniques to describe locations. Some people, especially when using geographic information systems (GIS), utilise three Cartesian co-ordinates (X, Y, and Z) to specify locations on the earth?s surface where X is the longitude, Y is the latitude, and Z is the altitude of the point. The co-ordinates for Suburb#1 are: X = -105? 02?’ 30?; Y = 39? 59?’ 47?; Z = 5180. The co-ordinates for Suburb#2 are: X = -112? 08?’ 08?; Y = 33? 51?’ 55?; Z = 1860.

The third Cartesian co-ordinate ? Z ? does not always refer to the altitude of the land surface. Sometimes, such as in mine planning software, Z refers to the height above or below the land surface. For example, the alluvial gravels of the river near Suburb#2 occur as three distinct alluvial deposits. The upper deposit (Z = 0 to -4.5 metres) consists of an even mix of sand and gravel and generally meets the specification for durability and abrasion resistance after processing.

The middle deposit (Z = -4.5m to 9.1m) is slightly more clayey with larger sized gravel and slightly more coarse sand than the overlying deposit. It is lower quality than the upper deposit and waste factors increase by about three per cent.

The bottom deposit (Z = -9.1m to about -13.7m) is the lowest deposits that could be extracted without extensive inter-burden removal. However, it generally does not make construction grade aggregate unless it is blended with other, higher quality, material.

If you are wondering where on earth I am talking about, Suburb#1 is Anthem at Broomfield, Colorado, and Suburb#2 is Anthem at Phoenix, Arizona. I chose these two places to use as an example because, by the time you read this article, I will have retired from the US Geological Survey and my wife Pam, our dog Rosie and I will have moved from Suburb#1 to Suburb#2 where we will live directly across the street from our daughter (and only child) Kimberly, our son-in-law (more like our son) Rob, and grandkids Donovan (8) and Delaney (7).

So I guess I could have employed texting shorthand and titled this article:
XYZ – Xit #229. Y? Catch some Zs.
Author?s note: The past 24 articles have taken you from A to Z. Now it is my turn to go to AZ.

Leave a Reply

Send this to a friend