Geographic information systems and mapping agricultural land

what do GIS programs allow us to do?

analyse and understand spatial data.

what is spatial data?

information on the geographic location of ‘things’

what’s the 1st law of geography?

everything is related to everything else but near things are more related than distant things.

what is the most common way to measure the location of places worldwide?

longitude and latitude

what can knowing the size of farms allow for?

calculating area based government payments.

what can knowing field area allow for?

calculating seed volumes for seed rates.

what have government agencies used spatial data and GIS for?

to allocate funds

what 3 examples of spatial data are there?

• area of habitats on farms,

• length of streamside corridor,

• number of mature trees.

what are field parcels outlined with and why?

red boundaries to be easily identified

what will selected field parcels be outlined with?

a blue border

what are most permanent features shown with?

red hatching

what do red dots represent?

scree, rock outcrops, boulders and sand.

what are the 2 main types of data?

spatial date and raster data.

what is raster data in GIS?

grid of discrete cells or pixels that represent on, above or below the earth’s surface. each cell in the raster grid is the same size, and cells are often rectangular.

what is raster data very good at representing?

continuous data.

what are the 4 main properties of raster data?

1. cell co-ordinate (usually lower left hand corner),

2. resolution (or grain = ‘size’ of the cells/pixels),

3. value of the data in the cells,

4. which coordinate system used.

what is the xll?

the value of lower left hand corner of the x-axis = 0

what is the yll?

the value of the lower left hand corner of the y-axis = -1

when colours are seen, what is the data actually stored as?

a grid of numbers. the software converts the numbers to colours for our benefit.

what is vector data?

data used to represent geographic objects through geometric shapes. It can be categorised into points, lines or polygons.