Cartographical Whispers

Dr Nigel TroddCoventry University

Your (very simple) AIM:

construct a map of the area between the library and

Coventry Cathedral

You will need Blank A4 sheet Ruled A4 sheet x2 Acetate sheet Graph paper Pencil and / or Colour pens Ruler or other straight edge Common sense

Start exercise

Task 1Draw a sketch map of the area on

one of the blank A4 sheets

buildings roads, footpaths railway lines rivers bridges parks, cemeteries and open spaces trees & street furniture Etc.

Pass to a neighbour

Task 2Identify the entity type of each phenomenon – is it a

Point Line Area

Record this information on the sketch map

Pass your list of entity types and the original map to a neighbour

Task 3

Create a vector map using the original sketch map annotated by entity type

Draw the map on an acetate sheet

Pass the original map, list of entity types and vector map to a neighbour

Task 4Choose one feature and convert its’ vector map to a raster map

Use graph paper for your raster map Allocate a code to each cell You may find it sensible to code blocks

of cells. If you do, make sure that you only code square blocks.

Pass the original map, vector and raster maps to a neighbour

Task 5Create vector and raster data files Use the graph paper to establish a coordinate system Raster file – you will need to record information on

the array size and cell resolution as well as the presence / absence of a feature in a cell.

Vector file - identify the coordinates of nodes & points of all objects in a feature class. Your data file will also list object identifiers and number of coordinate pairs to ‘close’ an object.

remember: raster files assume an origin in the top left (row 0, column 0), vector files in the bottom left.

Pass all maps and lists to the original cartographer

Task 6 Do the maps look anything like your

original sketch? Have the features been correctly

identified and accurately located? How are complex features represented

e.g. bridges, trees in open spaces, pathways alongside roads?

What do you think are the main sources of uncertainty?

Summary

Digital model of the real world:

geographical phenomena spatial entities data models & data structures