2.1. Visualisation of spatio-temporal data

2.1.1. Static data

PCRaster includes the Aguila software for visualisation of spatio-temporal stochastic data. With Aguila, you can easily explore large multi-dimensional data sets. For the exercises below, you will need to look up some options in the Aguila manual, available at https://pcraster.geo.uu.nl/pcraster/latest/documentation/pcraster_aguila/index.html.

You will use the data from an Alpine area that will also be used for the construction of the distributed model in the dynamic modelling exercises.

Aguila is started from a command shell. On Linux or Mac this would be a standard terminal window, on Microsoft Windows you need to open the command prompt. Open a command shell and go to the directory containing your data for the exercises. Type cd to change directories. In the directory, you will find the folder snowmelt containing the data for the visualisation practical. In this directory, display the digitial elevation model and another map with Aguila:

aguila dem.map anArea.map <Enter>

Use the menu items (or right click on the legend to get more options) to zoom in/out, to change the color palette, and to change the drawing mode to contours. Also try changing the number of classes shown (or number of contours).

Question: What is shown on anArea.map?

  1. True cells represent the higher part of the study area.

  2. Idem, lower part.

Correct answers: a.

Feedback: None.

You can also combine multiple maps in one view:

aguila anArea.map + dem.map <Enter>

The second map is draped over the first map. Make dem.map transparent by changing its display mode to contours. Now you are able to see both maps in one view.

2.1.2. Temporal spatial data

Temporal spatial data can be animated in PCRaster. The dataset contains a timeseries of maps with the amount of precipitation (m/day) in the area. It consists of 181 maps, each map contains precipitation for one day. The first map represents July 1st. Type dir <Enter> (or ls if you are on Unix) to get a list with all files in your dataset. You will see it contains the files precip00.001 up to precip00.181. These are the precipitation maps. To display them, type:

aguila --timesteps=[1,181,1] precip <Enter>

Animate the maps by clicking on the yellow menu item at the top of the view. Create a time series plot by right clicking on the legend, selecting ‘Show time series’. The time series is plotted for the current cursor position on the map (so you can get a time series for any location, try it!).

Now, type:

aguila --timesteps=[60,181,10] precip <Enter>

Animate. It has opened a subset of maps now, i.e. map 60, 70, 80,.. up to 180. So the first value (60) that you provide between the square brackets is the first time step to be shown, the second value (181) is the last step, and the third value (10) is the number of time step between the maps that are shown.

Question: Compare the precipitation pattern with the elevation map (open them in one view, using a single Aguila command). What is the relation between precipitation and elevation?

  1. There is no relation.

  2. The higher the elevation, the higher the precipitation.

  3. The lower the elevation, the higher the precipitation.

Correct answers: b

Feedback: None

2.1.3. Temporal non-spatial data

You can also use observed timeseries of data in Aguila, e.g. observed precipitation at a meteo station. Such data are non-spatial (single location, or sometimes multiple locations). Have a look at the contents of a rainfaill timeseries included in the data set by typing:

type precip.tss

(on a Unix system you will use less). The time series file is an ASCII file (just like for instance python programs being ASCII files) and thus can be displayed with the standard command type. You could also open it in an ascii editor. The first column contains the time steps numbers (here each time step represents a day), the second column the observed value (here: precipitation in m/day). Display the timeseries by typing:

aguila precip.tss