A vector is a line that has a start, direction and end

whereas a raster is a collection of dots or pixels.

Thus a vector image or drawing is created using lots of lines. Even a curve is constructed using straight lines. Just lots of them

A raster image or drawing is created purely with dots. Thousands upon thousands of them. Each with their own colour.

Geo-referencing can be thought of as repositioning, re

scaling or rotating an image or plan to corresspond with its real life scale and co-ordinate locaton on our planet's surface. Of course this still takes place on a screen, the only difference being your image (in this case a map) now has a place relative to the aerial photography from Google Earth.

A software program that can create, manage and analyze data that is geographically linked.

Most GiS work with layers with a layer being a type of data. For example a road layer contains line data. A land boundary layer contains polygons or shapes. A tree layer contains points and so on. Now think of these layers like transparencies sitting on top of each other. Layers that are all linked by a common location.

QGiS (previously known as Quantum GiS) is a free and open-source cross-platform

GiS application that supports viewing, editing, and analysis of geospatial data.

Known for its processing abilities QGiS is widely recognised as one of, if not the best GiS package available. Portable Mapper's core functionality relies on QGiS.

With the world being round (well almost) that does create some difficulties for those producing maps. So to make life easier most countries have their own flat plane projected co-ordinate system like a flat piece of card sitting on top of a sphere.

Here in Great Britain we use the British National Grid. Often refered to as BNG or more correctly EPSG:27700.

Each square on the map is 100 x 100km with the bottom left of SV in Cornwall being 0,0. With co-ordinates being traditional written as 6 figure Eastings (bottom numbers) and 6 figure Northings (numbers on right).

You've probably heard this term a lot but if you want to know a little more about it then please read on.

GPS is an abbreviation for Global Positioning System and it's found on our everyday items such as in cars and on our mobile phones. GPS works through a technique called trilateration where time, location, velocity and elevation are calculated. Similar to triangulation where the angle is used but in this case it's velocity.

At least 4 satellites orbiting the earth are required, each sending a signal to your GPS device. Each signal recording the time taken to travel at a certain velocity (speed). And with time and velocity known, you can then calculate the distance. Distance = Velocity x Time. Knowing the distance from 4 separate satellites allows an approximate location on the earth's surface. More satelittes equals higher accuracy.