Reviewer 1 of ICRA 2011 submission 870

Comments to the author
======================

The paper has problems with the introduction which I
describe below.   However, the core of the paper has some
useful ideas, particularly the weighting of visual words,
the measure of information gain that is used, and the
overall system design.	 I was also impressed with the
real-world experimental results on urban roads.  
Therefore, I believe the paper will be of value to others.

The introduction needs more careful work, as it describes
mostly work done 5 or 10 years ago rather than the latest
systems.   Therefore, it seems to set up straw-man
arguments, such as the comment on planar facades in
paragraph 2 that do not apply to modern work.	Instead,
the authors should carefully review modern work, such as
that of Newman's group, and discuss how this work builds on
the best previous approaches.

Similarly, the authors reference the related work of
Schindler et al., but fail to precisely describe the
relationship and differences with the work in this paper. 
Is the information gain measure the same?   If so, it
should be clearly referenced, with any differences
identified.  Without this context, the paper appears
disconnected from or ignorant of recent research and will
be ignored by others.

The claim that Indian roads require a different approach is
not convincing, as every country will have a wide range of
conditions in different locations which a robust system
must handle.   Instead, it would be best to make just a
brief mention of this in the introduction and then possibly
give more details in the experimental section where
particular data is described.	This also avoids having the
paper being viewed as only relevant to a limited
environment.

The abstract should also be lengthened to mention the key
technical contributions.
