[pgrouting-users] How to interpret the outcome of pgr_analyzeGraph()

[Kaiser Asif]

I got the following message output from pgr_analyzeGraph():

NOTICE:  PROCESSING:
NOTICE:  pgr_analyzeGraph('activity_
linestrings_edge_table_noded',0.0001,'the_geom','id','source','target','true')
NOTICE:  Performing checks, pelase wait...
NOTICE:  Analyzing for dead ends. Please wait...
NOTICE:  Analyzing for gaps. Please wait...
NOTICE:  Analyzing for isolated edges. Please wait...
NOTICE:  Analyzing for ring geometries. Please wait...
NOTICE:  Analyzing for intersections. Please wait...
NOTICE:              ANALYSIS RESULTS FOR SELECTED EDGES:
NOTICE:                    Isolated segments: 62
NOTICE:                            Dead ends: 227
NOTICE:  Potential gaps found near dead ends: 7
NOTICE:               Intersections detected: 1760018
NOTICE:                      Ring geometries: 8
Total query runtime: 512185 ms.

- What do the last 3 count means?
- Does the *intersection* count means that the graph needs to be "noded" so
that all intersections are converted into nodes? how to do that? increasing
the tolerance in pgr_nodeNetwork() increased the number of intersections.
- on related note: why is there a tolerance in pgr_createTopology? What I
understand is: all edges shorter than the tolerance will be marked as loop
(sets target = source). So if AB and BC were segments from a trace and AB <
tolerance, then the result is AA and BC. ABC path becomes disconnected. I
don't want that.

Thanks,
Kaiser.
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