Friday, May 26, 2017

Instruments For Navigation & Surveying

February 29, 2016 by  
Filed under Technology

When we think of professions, typically people garner up images of workers they see every day. This includes our own co-workers as well as people such as bank tellers, waiters, insurance providers, doctors, lawyers and so on. Surveyors aren’t workers that people might think of daily, but these individuals are quite important to society, and they use a wide variety of unique tools and instruments, such as the surveyor’s compass, theodolites and the Jacob staff.

There are many different types of compasses aside from the tiny handheld device that you might be familiar with from your scouting days. The compass in general is simply a device that identifies the direction of magnetic north in relation to the location of the compass. Obviously, this is quite helpful for navigation, but the surveyor’s compass goes a bit further than a regular compass. The surveyor’s compass or circumferentor not only provides the location of magnetic north, it also can be used to measure angles in the horizontal plane.

We all know what a typical compasses looks like, it’s simple a round device that is labeled with direction and features a magnetic needle. This needle is the part that points to magnetic north to help hikers and navigators and others determine direction. With a surveyor’s compasses, additional tools are added to help with measurement. A sighting device is mounted onto the surveyor’s compass and placed onto the north-south axis. From there, you would mount this compass onto some form of tripod and sometimes on a Jacob staff prior to use.

This Jacob staff, which is named in honor of the biblical Jacob, has several uses and is sometimes called by other names. This device dates back to the 1300s and was invented by a mathematician who used the Jacob staff for mathematical calculations, such as measuring distances. Often this was a tool used by sailors and astronomers. When we discuss the Jacob staff as it pertains to surveying, this was simply a rod on which a surveyor’s compass is mounted. Often it would be placed into the ground to help hold the compass steady and can still be used that way today.

While it’s not uncommon to see a surveyor’s compass mounted to a Jacob staff, other types of compasses can be mounted to the Jacob staff as well as other tools. For instance, you might place a level on a Jacob staff, such as an Abney level. This type of level is a device used by land surveyors, and it includes a sighting tube as well as a protractor scale. Another item that one might place on a Jacob staff is the graphometer, which also resembles a protractor and is used for angle measuring.

In some cases, surveyors might prefer using a tripod instead of a Jacob staff. This is particularly true when the device being used is quite heavy. When using a theodolite, for instance, a tripod is the standard option for mounting. Theodolites, which measure both horizontal and vertical angles, are perhaps the most commonly used surveying devices today.

Carey Bourdier loves writing about precision scientific instruments. For more details about alignment tools such as a maple wood Jacob Staff, go to the Warren Knight site now.

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