for the merge
This commit is contained in:
Binary file not shown.
@@ -82,8 +82,6 @@
|
||||
\usepackage{algorithm}
|
||||
\usepackage{algpseudocode}
|
||||
|
||||
\usepackage{caption}
|
||||
\usepackage{subcaption}
|
||||
|
||||
|
||||
% replacement for the SI package
|
||||
|
||||
@@ -32,9 +32,10 @@ As the Galaxy's \docWIFI{} can not be limited to the \SI{2.4}{\giga\hertz} band
|
||||
Additionally, the Galaxy's barometer sensor provides fare more inaccurate and less frequent readings than the Nexus does.
|
||||
This results in a better localisation using the Nexus smartphone.
|
||||
The computation for both filtering and smoothing was done offline using the aforementioned \mbox{CONDENSATION} algorithm and multinomal (cumulative) resampling.
|
||||
For each path we deployed 10 MC runs using \SI{2500}{} particles and $500$ sample realisations for BS.
|
||||
%However, the filter itself would be fast enough to run on the smartphone itself ($ \approx \SI{100}{\milli\second} $ per transition, single-core Intel\textsuperscript{\textregistered} Atom{\texttrademark} C2750).
|
||||
%The computational times of the different smoothing algorithm will be discussed later.
|
||||
Unless explicitly stated, the state was estimated using the weighted arithmetic mean of the particles.
|
||||
Unless explicitly stated, the state was estimated using the weighted arithmetic mean of the particle set.
|
||||
|
||||
As mentioned earlier, the position of all \docAP{}s (about 5 per floor) is known beforehand.
|
||||
Due to legal terms, we are not allowed to depict their positions and therefore omit this information within the figures.
|
||||
@@ -84,23 +85,15 @@ This focuses the computational resources of the FBS into regions with high proba
|
||||
Since smoothing operates on known states, the danger of sample impoverishment is negligible.
|
||||
|
||||
|
||||
We deployed 10 MC runs using \SI{2500}{} particles for approximation and a multinomial resampling step to every smoothing interval of the FBS.
|
||||
We deployed a multinomial resampling step to every smoothing interval of the FBS.
|
||||
Now, the positional average error along all 4 paths using the Nexus and the Galaxy could be improved from \SI{2.08}{\meter} to \SI{1.37}{\meter}.
|
||||
Using the same number of particles and $500$ sample realisations the BS performs with an average error of \SI{2.21}{\meter} for filtering and \SI{1.51}{\meter} for smoothing.
|
||||
The BS performs with an average error of \SI{2.21}{\meter} for filtering and \SI{1.51}{\meter} for smoothing.
|
||||
The difference between both filtering steps is of course based upon the randomized behaviour of the respective probabilistic models.
|
||||
It is interesting to note, that the positional error is very similar for both used smartphones, although the approximation error varies greatly.
|
||||
Using the FBS, the Galaxy donates an average approximation error of \SI{4.03}{\meter} by filtering with \SI{7.74}{\meter}.
|
||||
In contrast the Nexus 6 filters at \SI{5.11}{\meter} and results in \SI{3.87}{\meter} for smoothing.
|
||||
The BS has a similar improvement rate.
|
||||
|
||||
A visual example of the smoothing outcome for path 3 is illustrated in fig. \ref{fig:int_path3_a}.
|
||||
It can be clearly seen, how the smoothing compensates for the faulty detected floor change using future knowledge.
|
||||
|
||||
|
||||
The estimation of BS looks way more realistic and adapts better to the ground truth path.
|
||||
%However, in this particular example the FBS starts at an earlier position (cf. fig. \ref{fig:intcomp} seg. 2), better handling the initial uniform distribution.
|
||||
%Another advantage of BS over FBS, is the ability to still improve the filtering results even while reducing the number of particles radical.
|
||||
%For example \SI{50}{} particles and \SI{25}{} sample realisations are providing reliable estimations similar to above experiments, though the risk of losing track is higher.
|
||||
|
||||
\begin{figure}
|
||||
\begin{subfigure}{0.175\textwidth}
|
||||
@@ -113,23 +106,25 @@ The estimation of BS looks way more realistic and adapts better to the ground tr
|
||||
\caption{}
|
||||
\label{fig:int_path2_b}
|
||||
\end{subfigure}
|
||||
\caption{a) Exemplary results for path 2 where BS (blue) and filtering (green) using 2500 particles and 500 sample realisations. b) A situation where BS smoothing was not able to improve the filtering results. Two main factors are causing this: an initial position within a detached room and inaccurate pressure readings given by the Galaxy S5.}
|
||||
\label{fig:int_path3_comp}
|
||||
\caption{a) Exemplary results for path 2 where BS (blue) and filtering (green) using 2500 particles and 500 sample realisations. b) A situation where smoothing provides a worse error in regard to the ground truth, but obviously a more realistic path.}
|
||||
\label{fig:int_path2}
|
||||
\end{figure}
|
||||
Despite the very good outcomes provided by both interval smoother, there are some rare situations in which smoothing does not improve the filtered estimation or even improves the visual path.
|
||||
For example fig. \ref{fig:int_path3_b} depicts such a situation for path 3 using BS and measurements provided by the Galaxy S5.
|
||||
Here, the estimation was not able to change floors correctly due to faulty pressure readings. Additionally, the initial position was located within a detached room.
|
||||
This shows that the smoothing results are of course highly depend upon the filtering performance.
|
||||
%
|
||||
Two visual examples of the smoothing outcome for path 2 are illustrated in fig. \ref{fig:int_path2}.
|
||||
It can be clearly seen, how the smoothing compensates for the faulty detected floor changes using future knowledge.
|
||||
Additionally, the initial error is reduced extremely, approximating the pedestrian's starting position down to a few centimetres.
|
||||
In the context of reducing the error as far as possible, fig. \ref{fig:int_path2b} is a very interesting example.
|
||||
Here, the filter offers a lower approximation and positional error in regard to the ground truth.
|
||||
However it is obvious that smoothing causes the estimation to behave more natural instead of walking the supposed path.
|
||||
This phenomena could be observed for both smoothers respectively.
|
||||
|
||||
At next, we discuss the advantages and disadvantages of utilizing FBS and BS as fixed-lag smoother.
|
||||
Compared to fixed-interval smoothing, timely errors are now of higher importance due to an interest on real-time localization.
|
||||
Especially interesting in this context are small lags $\tau < 10$ considering filter updates near \SI{500}{\milli\second}.
|
||||
Fig. \ref{} illustrates the different estimations for path 4 using a fixed-lag $\tau = 5$.
|
||||
The associated approximation errors alongside the path can additionally be seen in fig. \ref{fig:lag_error_path4}.
|
||||
For better distinction, the path was divided into $10$ individual segments.
|
||||
|
||||
%Path 4 grafik mit fixed-lags
|
||||
|
||||
%
|
||||
%wie gut ist fixed-lag mit einem lag = 5. was fällt so auf?
|
||||
Fig. \ref{fig:lag_error_path4} illustrates the different approximation errors alongside path 4 using $500$ particles, \SI{100}{sample realisations} for BS and a fixed-lag $\tau = 5$.
|
||||
%
|
||||
\begin{figure}
|
||||
\input{gfx/eval/lag_path4_error/error_timed_costum}
|
||||
@@ -143,9 +138,9 @@ Besides the positional quality, also the timely error could be reduced by both a
|
||||
Once more, the BS outperforms the FBS by providing an overall approximation error of $\SI{4.86}{\meter}$ for the Galaxy and $\SI{2.97}{\meter}$ for the Nexus by filtering with $\SI{5.68}{\meter}$ and $\SI{3.15}{\meter}$ respectively.
|
||||
Whereas FBS is not able to reduce the filtering error, obtaining $\SI{5.59}{\meter}$ using the Nexus and $\SI{3.12}{\meter}$ the Galaxy.
|
||||
However, this does not mean, that the FBS is unpracticable for problems of fixed-lag smoothing.
|
||||
By looking at the data in detail, high errors similar as seen in fig. \ref{fig:lag_error_path4} occur on path 3, which cause the estimation to behave more natural instead of walking the supposed path.
|
||||
This phenomena could be observed for both smoothers respectively.
|
||||
Also note the difference between this error, including timely information, and the positional error used before.
|
||||
%By looking at the data in detail, high errors similar as seen in fig. \ref{fig:lag_error_path4} occur on path 3, which cause the estimation to behave more natural instead of walking the supposed path.
|
||||
%This phenomena could be observed for both smoothers respectively.
|
||||
%Also note the difference between this error, including timely information, and the positional error used before.
|
||||
%The median errors for all conducted walks are listed in table \ref{}.
|
||||
Similar to fixed-interval smoothing, decreasing the number of particles does not necessarily worsen the estimation.
|
||||
In most cases smoothing compensates for this reduction and maintains the good results.
|
||||
|
||||
Reference in New Issue
Block a user