GPS, Map and Google Earth

Although most of my posting are GPS related, I also want to post a basic navigation knowledge. You can use a full feature in your GPS if you know a basic navigation skill. Map and compass is the part of basic navigation, lets start with compass:

A compass, is a navigational instrument for finding directions on the Earth. It consists of a magnetized pointer free to align itself accurately with Earth's magnetic field, which is of great assistance in navigation. The face of the compass generally highlights the cardinal points of north, south, east and west.

Fundamentally, the classic compass is any magnetically sensitive device able to indicate the direction of the magnetic north of a planet's magnetosphere. Often compasses are built as a stand-alone sealed instrument with a magnetized bar or needle turning freely upon a pivot, or floating in a fluid, thus able to point in a northerly and southerly direction

There are various type of compass available in the market, generally, those can be divide to:
- small pocket compass
- liquid filled lensatic compass
- silva’s models orienteering compass
- military prism compass
- geological compass
- other compass

Both of the above compass are very common use by kids or boy scout for their basic navigation knowledge. The pocket compass is very simple with needle always pointed toward north. The lensatic is more precise and acurate, we can read up to 10 or 5 degree bearing acuracy through its lense.

Silva is a brand name of compass manufacturer, however later become a trade mark of orientering compass. It can be very simple like a rectangle plastic with round compass in the midle, up to a quite complicated orientering compass equipped with mirror, ruler, build in loupe, and sometimes with clinometer. The Prism compass premarily used by the military. This is my favorite compass, we can read less than 5 degree bearing through its prism. The liquid inside make the compass easy to stabilize. The ring is use to your thumb position when you are piping through the prism.

Like as Silva, Brunton’s compass is always associated with geological compass, there is some other monufacture produce geological compas i.e. Tamaya, Suntoo; however Brunton brand is the famous one. Geological compass equipped with: mirror, balance plate (some of them not), horizontal nivo, clinometer with nivo to measure rocks bedding strike and dip. Since I am a professional geologist, I’m very familiar with this type of compass.

Compass Reading Tips
- Hold the compass level
- Read the correct end of the needle (this one need more explaination, its depent of type of compass we use, I’ll write in other post)
- Keep the compass away from metal objects or other object that can influence a compass magnetic needle