Texas Advanced Computing Center - Visualization

VAST 2008 Challenge
Mini Challenge 2:  Migrant Boats (geo-temporal analysis)

Authors and Affiliations:

Jaya Sreevalsan-Nair, Texas Advanced Computing Center, jaya@tacc.utexas.edu  [PRIMARY contact]
Weijia Xu, Texas Advanced Computing Center

Student team: NO

Tool(s):

We developed our own visualization tool using OpenGL and C++  in  July 2008 to analyze the data presented in this challenge.  The tool helps us visualize the temporal and geographical patterns that the migrant boats have been using.  The tools has interactive features for looking at the launch sites from the  island, successful landing sites and interdiction points, for specific time periods. We also employ Computational Geometry Algorithms Library (CGAL) for computing  features of various selected point-sets  either landing sites or interdiction sites. Our tool also can show the trends the various U.S.Coast Guard ships have been following, and how the  patterns of the  migrant boats and USCG learn and evolve  over time. We have used textures of Florida  and Isla del Sueno maps to give a reference of latitude and longitude. Time is plotted in the z axis to the project the landing and interdiction points in three-dimensional space.

Two Page Summary:   NO

ANSWERS:

Boat-1 Characterize the choice of landing sites and their evolution over the three years.

Detailed Answer:

Initially the landing sites were chosen to be along the coast of Florida. Over time, they have tended to move northwards owing to the pattern of the interdictions in mid-latitudes. The regions of interdictions have tended to expand as well, but the regions of landing sites have expanded even further. Given below are the bounding boxes (the bottom left and top right corners) of the interdiction points and landing points (each corner of the bounding box is represented as (longitude, latitude)).

Year: Bounding box of interdiction: Area of the bounding box (assuming latitude-longitude mesh as a grid)
2005: (-81.8208, 24.0632), (-79.2672, 25.9186) : 4.73794944
2006: (-82.7533, 23.4135), (-79.5271, 26.638)   : 10.4028819
2007: (-83.2201, 23.2945), (-79.3664, 28.1035) : 18.5324433

Year: Bounding box of interdiction: Area of the bounding box (assuming latitude-longitude mesh as a grid)
2005: (-82.1222, 24.5384), (-80.1009, 26.0972)  :  3.13677324
2006: (-86.7137, 21.2016), (-80.3158, 29.1763)  : 51.02133313
2007: (-86.8028, 21.2138), (-80.0277, 29.3211)  : 54.92776823

Inference from this analysis is that the expanse of the landing points have increased much rapidly over time, and the increase in the expanse of the interdiction points is much slower. However as shown in the image, the trend of the interdiction points are slowing moving towards that of the landing points.

Figure 1-1: (Left) Using z-axis to plot time to plot all the interdiction and landing points. One can see the clusters of points in the second and third quarters of each year, indicating increased activations during that time. (Center) Black lines indicate the traces of each of the interdicting USCG over a period of time. The points indicate only the landing points over time. y-axis indicates the latitude. This image shows how the concentration of USCG increases in the second and third quarters of the year, over time, as is the trend of migrant boats. However, one can see how the expanse of interdictions across latitudes is much lower than that of landing. The migrants have cleverly learnt to seek northern and southern destinations for successful landings. (Right) The violet lines and points indicate the moving least square fitting line and centroid of the landing points over the years; and the red indicates the same for the interdiction points. It again indicates how the trend of interdictions are moving towards that of the landing points, but in a much slower fashion. The southward movement of the centroid of the landing points indicate how the migrants are taking the southern route more frequently, which has not yet been intercepted by U.S.Coast Guard. In all images, orange points indicate Go Fast boats, yellow are Raft and peach-colored are Rustic.

Figure 1-2: (Left) Interdiction points and (Right) landing points between Florida coast and Isla del Sueno in 2005-07. Orange points indicate Go Fast boats, yellow are Raft and peach-colored are Rustic. These images show how most of the interdictions happen in the zone between the island and the Florida coast, and interestingly the landing points form the Florida coastline, and are expanding northwards. The later attempts of landing are made in destinations south-west of the island. This is either an anomaly or new destinations and routes are being experimented with.

Figure 1-3: Launching directions for (Left) interdiction points, and (Right) landing points for 2005-07. Successful routes tend to be repeated. The launches from northwestern part of the island to either western coast of Florida or the southwestern routes have higher success rates. Hence the landing points are chosen based on successful routes in the past as well.


 

Boat-2  Characterize the geographical patterns of interdiction over the three years

Short Answer:
As shown in Figure 2-1, the centroid of interceptions moves slowly towards the centroid of landings over time. However the direction of movement of centroid of interceptions is the same as that of the landings. The linear least square fitting line of the interceptions changes from positive to negative slope, indicating the interceptions are slowly aping the trend of the landings and are getting scattered, though still concentrated highly in the zone between the Florida coast and the Isla del Sueno coast. The bounding box of interception points has increased in expanse over time, and has been increasing in leftward and northward. However their increase of areas of bounding box is very slow in 2005-06; however it is accelerating steadily in 2006-07.

 Figure 2-1: The violet lines and points indicate the moving least square fitting line and centroid of the landing points over the years; and the red indicates the same for the interdiction points. It  indicates how the trend of interdictions are moving towards that of the landing points, but in a much slower fashion. Orange points indicate Go Fast boats, yellow are Raft and peach-colored are Rustic.

Boat- 3 What is the successful landing rate over the time period?

Short Answer:
Successful landing rate over the entire time period is 48.03%. The annual successful landing rate over the time period has steadily increased from 30% to 43% to 57% in 2005, 2006 and 2007, respectively. The different types of boats individually show similar behavior. In 2007, the number of successful landings shoot higher than that of interdicted boats. The increase in successful landing rate can be attributed to increase in the number of boats used over the years, and the more intelligent choices of landing northwards and southwards, to beat the U.S. Coast Guard.