1. Features that make a map
Houzhai Catchment
Title
Legend
Scale
Projection
Graticule/North Arrow
Data
Labels

2. Projection Systems – why you care
Geographic Coordinate Systems
A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define locations on the earth.
e.g. WGS84
Projected Coordinate Systems
A projected coordinate system is defined on a flat, two-dimensional surface. In a projected coordinate system, locations are identified by x,y coordinates on a grid, with the origin at the center of the grid
e.g. OSGB 1936 / British National Grid

3. Projected coordinate systems – projectable surfaces
e.g. Universal Transverse Mercator (UTM) coordinate system
Equal distance
Conformal (no angular deformation)
Equal area

4. The process of transforming part of a non-planar surface to a planar map results in distortion of at least one of the spatial properties of distance, scale, direction, angle, shape, and area. Several hundred projections have been developed which preserve one or more of these properties.
Choice of map projection should account for location and area of the shape to be mapped, geometric properties most valuable to the data, and mapping purposes
Conformality: No angular deformation occurs. This projection class is important for navigation charts, topographical maps, and military maps
Equivalence (equal-area): Any area on the Earth will occupy the same area on the 2D projection. This property is most valuable to distribution mapping (eg. population statistics), where an accurate impression of density is important.
Equidistance: The scale in one direction is always correct, eg. the lines of latitude or longitude are always the same length as on the Earth. Equidistant maps preserve neither angles or area (hence are never conformal or equivalent), but can provide a good compromise in that maximum angular deformation and maximum area deformation are less than that of equal-area and conformal maps respectively.
Minimum-error representation: A minimum error map aims to minimise the sum of the squares of scale errors across the map. An absolute minimum-error map will minimise the sum of all errors, and is a special property in itself, but minimum-error representations may be combined with another special property as a compromise.
Snyder’s decision tree
1. ‘Shape’
Predominant east-west extent
Predominant north-south extent
Predominant oblique extent (eg.:North America, South America, Atlantic Ocean)
Equal extent in all directions (eg. Europe, Africa, Asia, Australia, Antarctica, Pacific Ocean, Indian Ocean, Arctic Ocean, Antarctic Ocean)
Location – centered on poles/equator/mid-latitude
Then pick projection based on special property of interest

5. Raster Data Vector Data
Raster models are useful for storing data that varies continuously.
e.g. elevation surfaces, temperature, spectral response, digital aerial photographs, satellite imagery, scanned maps
Area of map is divided into a grid of cells
Each cell is assigned a value
High data volume – slow to load/analyse
Many different file types count as rasters, e.g.
.img, .tiff, .gtiff
A representation of the world using points, lines, and polygons
E.g. Roads, buildings, fences, property boundaries
Points, lines, or polygons defined by geographic coordinates
Low data volume – fast to load/analyse
accurate geographic location of data is maintained
Attributes can be attached to classes
Standard file formats: .shp (point, line, polygon)

6. Making your own map
Software
QGIS
Open-source, available on Windows, Mac, Linux
Esri ArcMap
Commercial, available at uni
Sources of free spatial data (remember to reference!)
World
United Kingdom
Roam capability
GIS download

7. Skye example Datasets Operations
Backdrop map  1: raster
Vector data  OS Open map local
Also google maps, bing, open street map all available as a basemap under Web  Open layers plugin
Also many other layers available in both raster and vector format e.g. geology, land cover, digital elevation models (DEM).
Check projection system
Check data source
Operations
Adding datasets to the QGIS catalogue: for every tile, specify projection system ‘OSGB 1936’
.tiff files for the backdrop map
.shp files for the woodland data
Combining .tiff tiles into one raster:
raster ->miscellaneous  merge  select relevant .tiff files from directory
Change colour palette: properties  style
Select ONLY the woodland on Skye (note there are 100s of ways to do this)
Layer  create new layer  shapefile  polygon  add to map  toggle editing  draw polygon . .  save edits  toggle editing  change transparency in properties  style
Vector  geoprocessing tools  clip  input layer is woodland, clip layer is polygon  save as new layer
Making a sampling grid within the woodland and export coordinates of grid
Vector  research tools  Random points/regular grid (whatever you want)  Skye woodland layer as input, save as new shapefile Skye grid
Get coordinates of points: Vector  geometry tools  export/add geometry columns  input Skye grid, save out as new shapefile or it will crash (QGIS doesn’t like overwriting shapefiles)
Export: right click on layer, save as, csv.

8. Other useful things Re-projecting datasets
Raster: Raster  Projections  Warp (reproject)
Vector: Right click on layer  save as  define new coordinate reference system
Importing datasets (e.g. list of points from a GPS)
QGIS accepts a lot of file formats
Layer  add layer  add delimited text layer
You can define the projection system that your coordinates are in after you have imported it under Properties  coordinate reference system but if you want to change the projection system you will need to follow the procedure above (save as a new file).