1. Radu Mariescu-Istodor
Winning the game Playing strategies for O-Mopsi
Lahari Sengupta
Radu Mariescu-Istodor
Pasi Fränti

2. What is O-Mopsi?

3. Classical orienteering
Devices: Map and compass
Targets brought to nature for the event
Motivation:
Orienteering is difficult to create and maintain. Easier with O-Mopsi.
Control points may be lost. Targets might become outdated in O-Mopsi.
Not everyone can play the game at 17:00. In O-Mopsi you can play at any time.
Disadvantages:
Battery, Weather,
Find all controls
In pre-defined order
Fastest wins 3

4. Mopsi orienteering (O-Mopsi)
Smartphone and GPS
Targets real objects
Pictures
of targets
Find all controls
In free order
Fastest wins

5. Challenges of playing ? Orienteering: Knowing your location
Optimizing paths to targets
O-Mopsi:
Finding best order
Optimizing paths to targets ?

6. Winning the game

7. What matters Order of visiting targets Where to start playing
Travelling salesman problem (TSP)
Human strategies: nearest neighbor, clustering
Computer strategies: optimal, optimization
Where to start playing
Remove longest edge from TSP?
Blind selection
Comparison of various heuristics
Navigating to targets
Effects of routing

8. Order of targets

9. Algorithmic problem Minimize total distance
With N targets there are N! possible orders
Variant of travelling salesman problem (TSP)
478 m
280 m
250 m
250 m
228 m
30 m

10. How much it matters? ? 5 km 4 km Nearest target strategy Optimal order3 2
More targets,
harder to solve
Nearest neighbor strategy
XX% longer than optimal (average)
Lahari: - Some calculations of distances of SciFest 2014 easy (min,max,median) - Algorithm variations with Helsinki - Overall, with the function of number of targets and complexity 1
5 km
Optimal order 3 ? 2
4 km 1

11. Effect of starting point

12. Where to start?
Targets not visible before start (if known, can start at one target)
No time for planning route (Time starts when game opens)
Game area (bounding box) shown
Start must be chosen blindly
Need two pics:
Before start
After start
Need to implement TSP with user-selected start point!

13. Start point strategy 1 Center of the area
x,x km
Center ?

14. Start point strategy 2 Corner of the area
x,x km ?

15. Start point strategy 3 Somewhere at the shorter edge
x,x km ?
Short
edge

16. Likely direction of optimal route
Start point matters
Every side has at least one target
Optimal order likely to go along longer side (rather than random zig zag)
Heuristic: Start from the shorter side
Likely direction of optimal route
xmax
ymax
Longer side
Start
Shorter side
xmin
ymin

17. Start point statistics according to target location
Optimal start point located:
First/last target along the short side: xx %
First/last target along the long side: xx %
Some other target: xx %

18. Start point statistics according to grid
Calculate optimal tour
Divide the area into 20%20% grid
Locate the start and end points of the tour in the grid
Longer side
Shorter side

19. Road network

20. Effect of route network Bird distance vs. roads
Buildings and small housing in city area
Real distance xx-yy % longer than bird’s distance
Can also affect the order of the targets
Bird distance
Routing
417 m
753 m

21. Effect of route network Start point changes
Bird distance
Routing
13.4 km
21.4 km

22. River has big impact 2.1 km 3.8 km Bird distance Routing crossing

23. Effect of transport mode
Shorter routing by walk
Routing by car

24. Limitations of routing
Limitations in street crossing
No shortcuts
No routes via open plaza