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| Subject: | RE: [gislist] GPS for capturing street centerline data |
| Date: |
11/14/2003 08:10:01 AM |
| From: |
Richard Nicoll |
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The issue of using geodata captured at various scales together can be
complex. In truth, it depends on what your final use will be and the
required accuracy of that use. Whilst within a GIS it is of course
perfectly possible to overlay GPS centrelines with a 50k raster, your
next steps are the issue. With a 50k map the road line itself will have
a substantial thickness, you may find that your GPS-derived vector fits
within this. You could run an edge-detection kernel through the raster
and convert the results to vector, you would expect to derive two
parallel vector lines for each road line edge. Is this useful? You
could also downgrade ('generalise') the accuracy of your GPS results by
removing some nodes or lowering the XY co-ord accuracy (eg make last two
numbers 0). Is this useful?
If you are wishing to update the 50k's at the same scale but using the
GPS as a new source of information then you might buffer your vector to
the thickness of the road in the 50k and compare the resulting polygon
extents. Often with a 50k map is not simply the accuracy but also the
presentation which is of importance (ie you could move features slightly
to prevent overlapping without major consequence) Without further
information it is hard to provide specific advise. Perhaps this will
help?
Rich
-----Original Message-----
From: Sonny Parafina [mailto:sonny@ionicenterprise.com]
Sent: 14 November 2003 13:38
To: Ted Cisine: raghavendran@pixelinfotek.com
Cc: GIS List (GeoComm)
Subject: RE: [gislist] GPS for capturing street centerline data
There is an interesting section on street centerline capture methods in
this
report (see link below) on linear referencing systems. See the section
on
creating centerline databases, the study claims that $250 GPS can create
a
centerline with sufficient accuracy for most applications.
http://www.ncgia.ucsb.edu/vital/research/pubs/200204-LRsynthesis.pdf
Cheers,
Sonny Parafina
IONIC Enterprise
-----Original Message-----
From: gislist-bounces@lists.thinkburst.com
[mailto:gislist-bounces@lists.thinkburst.com]On Behalf Of Ted Cisine
Sent: Friday, November 14, 2003 7:28 AM
To: raghavendran@pixelinfotek.com
Cc: GIS List (GeoComm)
Subject: RE: [gislist] GPS for capturing street centerline data
We use GPS in vehicles to capture centerlines and feel it is the best
way
(our maps are 1:100 to 1:400). I have never done it at 1:50000 but I
still
think GPS would be the easiest way to capture and you will have clean,
accurate data to use if you ever need to do something else with the
data.
Ted
_____________________________
Ted Cisine
GIS Manager
Robeson County Tax Administration
Lumberton, North Carolina
ted.cisine@co.robeson.nc.us
_____________________________
-----Original Message-----
From: gislist-bounces@lists.geocomm.com
[mailto:gislist-bounces@lists.geocomm.com]On Behalf Of SRG
Sent: Thursday, November 13, 2003 10:30 PM
To: gislist@lists.thinkburst.com
Subject: [gislist] GPS for capturing street centerline data
Importance: High
Sorry to post this one more time.
Does anyone have any ideas/ suggestions
Thanks for your time
SRG
_______________________________________
R A G H A V E N D R A N . S
GIS Analyst
@__^12.98N__>77.58E
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++
+++++++++++++++++++++++++++++
I have been analysing the pros and cons of going for a GPS survey to
capture
the highway centerline data.(+/- 3m accuracy)
The project is basically to create a base map of the state highways from
the
available departments maps (usually 1:50000 scale).
The next item would be to perfect the centerline data captured on the
digital maps with the information collected from the GPS survey (by
driving
along the state highways with a GPS fitted vehicle).
My question is simple:
The GPS data captured will be so accurate, reflecting every small curve
on
the highway again depending on the interval at which the GPS data is
captured.
How rational it would be to use/ integrate this data on a map of 1:50000
scale?
Thanks
SRG
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