Movement on maps: Beyond the travel record¶
Look at this map.... Did you notice that there changes along the x axis?
Charles Joseph Minard’s visualization of Napoleon’s Russian campaign of 1812, (Tufte, 1983)
Content¶
- Definition and purpose of flow maps
- Different types of flow maps (charts)
- Cartographic design principles (suggestions and limitations)
- Examples in real world data: Fluvial Engineering
Definition¶
It is a type of thematic map, with the main purpose of represent, with the purpose of representing movement. For some author (Dodge et al., 2008), is a kind of hybrid map: a base map with flow diagram.
Common characteristics in visual variables:
- Shape: Dot and lines
- Orientation, Size and Colour: Depends on the attribute of the data, weight and frequency
Types¶
- Sankey Diagrams
- Chords
- Origin Destination (OD)- Flow maps
- Streamlines, streaklines and Pathlines
In [11]:
# OD Matrix, available on https://plotly.com/python/lines-on-maps/
print('OD Dataset size {}'.format(df_flight_paths.shape))
df_flight_paths.head()
OD Dataset size (178, 8)
Out[11]:
| start_lat | start_lon | end_lat | end_lon | airline | airport1 | airport2 | cnt | |
|---|---|---|---|---|---|---|---|---|
| 0 | 32.895951 | -97.037200 | 35.040222 | -106.609194 | AA | DFW | ABQ | 444 |
| 1 | 41.979595 | -87.904464 | 30.194533 | -97.669872 | AA | ORD | AUS | 166 |
| 2 | 32.895951 | -97.037200 | 41.938874 | -72.683228 | AA | DFW | BDL | 162 |
| 3 | 18.439417 | -66.001833 | 41.938874 | -72.683228 | AA | SJU | BDL | 56 |
| 4 | 32.895951 | -97.037200 | 33.562943 | -86.753550 | AA | DFW | BHM | 168 |
In [3]:
fig.update_layout(title_text = 'Feb. 2011 American Airline flight paths<br>(Hover for airport names)',
showlegend = False,
geo = dict(scope = 'north america',
projection_type = 'azimuthal equal area',
showland = True,
landcolor = 'rgb(243, 243, 243)',
countrycolor = 'rgb(204, 204, 204)',
),
)
fig.show()
Vector Fields Visualization¶
- Streamlines: Line which connects velocity vectors at an instance in time. It is like a snapshot.
- Streakline: A curved line formed by a string of fluid particles which have passed through a certain point.
- Pathlines: Also called particle tracking, it is a path which a fluid particle traces
In [58]:
fig = plt.figure(figsize=(15,5))
gs = gridspec.GridSpec(nrows=1, ncols=3)
# Varying density along a streamline
ax0 = fig.add_subplot(gs[0, 0])
ax0.streamplot(X, Y, U, V, density=[0.5, 1])
ax0.set_title('Varying Density')
# Varying line width along a streamline
ax1 = fig.add_subplot(gs[0, 1])
lw = 5*speed / speed.max()
ax1.streamplot(X, Y, U, V, density=0.6, color='k', linewidth=lw)
ax1.set_title('Varying Line Width')
# With a obstacle "Masking"
ax2 = fig.add_subplot(gs[0,2])
ax2.streamplot(X, Y, U, V, color='r')
ax2.set_title('Streamplot with Masking')
ax2.imshow(~mask, extent=(-w, w, -w, w), alpha=0.5,
interpolation='nearest', cmap='gray', aspect='auto')
plt.show()
Suggestions and Limitations¶
based on Jenny et al., 2018 and Andrienko et al., 2008
- Curved vs. straight lines: People prefer circular arcs for graphs drawings. Less likely to create ambiguous analyses
- Arrows vs. tapered flows: There is no consensus on which is better, it depends on the amount of data and the importance of the destination for the map.
- Flows between areas vs. flows between nodes: Was found that flows between clear nodes in OD instead of non amarked areas result in lower error rates.
Geometry design tips, available on Jenny et al., 2018)
Current limitations and methodologies available on Andrienko et al., 2008¶
An Application in Fluvial Engineering¶
Groynes in fluvial erosion, image avaiable on Buczyńska et al., 2018
In [46]:
%%html
<iframe src="https://aamontalvo.github.io/MagangueEsp2/index.html" width="900" height="800"></iframe>
References¶
- Andrienko, G., Andrienko, N., Dykes, J., Fabrikant, S.I. & Wachowicz, M. (2008) Geovisualization of Dynamics, Movement and Change: Key Issues and Developing Approaches in Visualization Research. Information Visualization, 7(3-4), 173–180. Available from: https://doi.org/10.1057/ivs.2008.23.
- Buczyńska, E., Szlauer-Łukaszewska, A., Czachorowski, S. & Buczyński, P. (2018) Human impact on large rivers: the influence of groynes of the River Oder on larval assemblages of caddisflies (Trichoptera). Hydrobiologia, 819(1), 177–195. Available from: https://doi.org/10.1007/s10750-018-3636-6.
- Dodge, S., Weibel, R. & Lautenschütz, A.-K. (2008) Towards a taxonomy of movement patterns // Towards a taxonomy of movement patterns. Available from: https://journals.sagepub.com/doi/epdf/10.1057/PALGRAVE.IVS.9500182 [Accessed 20 March 2023].
- Jenny, B., Stephen, D.M., Muehlenhaus, I., Marston, B.E., Sharma, R. & Zhang, E. et al. (2018) Design principles for origin-destination flow maps. Cartography and Geographic Information Science, 45(1), 62–75. Available from: https://doi.org/10.1080/15230406.2016.1262280.
- Tufte, E. (1983) The visual display of quantitive information. Graphic Press.
Movement on maps: Beyond the travel recordLook at this map.... Did you notice that there changes along the x axis?
Charles Joseph Minard’s visualization of Napoleon’s Russian campaign of 1812, (Tufte, 1983)