QUIZ 3: Preimages, Sensor Lattices, Sensor Fusion¶
Due date: 2026-01-31 23:59.
Recommended Resources:
- SF: Sensing and Filtering, Steven M. LaValle, PDF
- Recorded Lectures and Slides
Preimages¶
% Q1
%✅ The preimage ℎ⁻¹(𝑦) ⊆ 𝑋 is the set of all states consistent with observation 𝑦
%✅ Smaller preimages correspond to lower state uncertainty
%❌ If two different states have the same observation, the sensor must be noisy
%❌ If two different states have the same observation, the sensor is not repeatable
%✅ If ℎ is bijective, every preimage is a singleton
%❌ All preimages have the same cardinality
%❌ Preimages are always connected sets
%✅ Preimages partition the state space
% Q2
%✅ All states differing only in 𝜃 belong to the same preimage
%✅ The sensor cannot distinguish robot orientation
%✅ The preimage has dimension at least 1
%❌ The sensor uniquely determines the full state
%❌ The sensor is bijective
%✅ The partition induced by ℎ is invariant under changes in 𝜃
%❌ The observation space must include 𝜃
% Q3
%❌ Dominance implies both sensors are bijective.
%✅ ℎ₁ dominates ℎ₂ if every preimage of ℎ₁ is contained in a preimage of ℎ₂.
%✅ If ℎ₁ dominates ℎ₂, then ℎ₂ = 𝑔 ∘ ℎ₁ for some function 𝑔.
%❌ Dominance will depend on accuracy of both sensors.
%✅ Dominance compares information content, not physical sensor quality.
%❌ Dominance requires equal observation spaces.
%✅ Dominance defines a partial order on sensors.
%❌ All pairs of sensors are comparable under dominance.
% Q4
%❌ Both ℎ₁ and ℎ₂ must have identical numerical outputs.
%❌ Both ℎ₁ and ℎ₂ must have the same observation space.
%❌ Both ℎ₁ and ℎ₂ must be bijective.
%✅ ℎ₁ and ℎ₂ induce the same partition of 𝑋.
%✅ Each sensor dominates the other.
%✅ ℎ₁ and ℎ₂ carry the same information about the state.
%❌ The sensors must be physically identical.
%❌ Both ℎ₁ and ℎ₂ have singleton preimages.
%Q5
%❌ Time-dependent sensors are always bijective.
%❌ Time dependence ialways mproves sensor accuracy.
%✅If ℎ(𝑥, 𝑡) = ℎ(𝑥, 𝑡′) for all 𝑡, 𝑡′ ∈ 𝑇, then there is no information about when the state was sensed.
%✅The sensor ℎ(𝑥, 𝑡) = 𝑥 has one-dimensional preimages.
%❌ Time must appear explicitly in the observation space 𝑌.
%❌ The sensor ℎ(𝑥, 𝑡) = 𝑡 provides the state 𝑥 at time 𝑡.
%❌ Time dependence eliminates state uncertainty.
%❌ Time-dependent sensors must be absolute sensors.
Sensor Lattice, Sensor Fusion¶
%Q6
%❌ Fusion always produces a bijective sensor.
%✅ The fused preimage equals the intersection of individual preimages.
%✅ Fusion can reduce or preserve uncertainty.
%❌ Fusion can increase uncertainty relative to both sensors.
%✅ Fusion refines the partition of the state space.
%❌ Fusion requires identical physical sensors.
%❌ Fusion guarantees a unique state estimate.
%❌ Fusion requires identical observation spaces.
%Q7
%✅ The set forms a lattice under refinement.
%✅ The coarsest partition corresponds to a constant sensor.
%✅ The finest partition corresponds to perfect sensing.
%❌ All sensors are totally ordered.
%❌ Every sensor is comparable to every other.
%✅ Fusion corresponds to partition refinement.
%✅Dominance corresponds to partition refinement.
%❌ The sensor that yields the finest partition is always unique.
%❌ The sensor that yields the coarsest partition is always unique.
%Which statements correctly summarize the preimage-based view of sensing?
%✅ Sensors partition the state space
%✅ Better sensors induce finer partitions
%✅ Fusion corresponds to intersecting partitions
%✅ Dominance is defined via preimage inclusion
%❌ Sensors must be numeric to be compared
%❌ Noise is required to define preimages
%❌ Calibration always changes dominance
%❌ All sensors can be totally ordered
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Authors¶
Anna LaValle, Steven M. LaValle.
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