Many different things can be measured in fieldwork, for example the velocityThe speed of an object in a particular direction. of a river, the number of cars or the amount of litter in a particular location.
Numbers can also appear in other forms:
Nominal data - these are numbers that appear as categories, eg 1 = yes and 2 = no.
Ordinal data - these numbers have an order, eg the rank order of cities by population size. It is known that city 1 is more populated than city 2 and 3, but it is not known how many more people there are, as the spacing between each city is not equal.
Interval data - these numbers are similar to ordinal, but the difference between each number is equal, eg temperature is measured in degrees centigrade.
Ratio data - this is when there is a relationship between two sets of numbers, eg number of people per doctor.