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Friday, July 1, 2016

First Interpolation Experiment Fails

Hi Folks:

  I started to experiment with ARCGIS on-line and I noticed that geostatistical interpolation is offered.  Interpolation is used where you have some data points on a map but some areas of the map are missing data.  Now let us apply this to rapid transit.  Let us say that we have ridership figures for subway stations.  Several years ago, I got a shape file of subway station locations in New York City and part of the file was ridership values for various years such as total ridership, average ridership on weekends and so on.  Let us run a experiment using interpolation.  How would interpolation treat those areas not covered by the subway system?  The results are shown above to the right, but we must mention that perhaps that this may not be a good statistical rational for doing this experiment.  My aim was:   Using known ridership at various stations, can I project to areas that do not have a subway?  The map above may be a failure.

In the analysis below, I used Annual 2000 data.  The highest value for a particular station was  in the 8 - 9 million range.   ARCGIS online will ask you how you will project the data and I chose "Manual".   I added discrete ranges of data for example, 2M, 4M, 6M, 8M and 10M.  In the interpolation panel, you should add these values numerically, i.e. "2,000,000".  The results show those areas that can generate riders of that value if a station was in that area, everything else being equal.  Thus the eastern side of Brooklyn near Marine Park could generate 2M - 4M at a subway station annually, if a station existed in the particular region.  For Staten Island, though not shown would generate 0 - 2M.   In Staten Island, the SIRT station data had no ridership values for FY 2000 and I could not select this out.  Notice the areas of eastern Queens and Western Manhattan (Before Hudson Yards).  This is experimental process may not be appropriate for the data set available.  It is an old data set and much has changed since 2000, particularly in some sections in Brooklyn like Williamsburgh.  All of Staten Island is the lightest color.  I am not sure if bodies of water (NY Bay) effects the results.  Notice that eastern Queens looks like it could use some additional rapid transit facilities.  My cheap solution:   A basic light rail line running down a wide avenue with a private right of way.  These lines should fan out from the last easterly station terminals of the subway.  If extra money is available, if possible, the light rail lines should go underground near the last stops if possible and provide cross the platform transfers to the subway.  Since some of the terminals, such as Archer-Pasrsons have two trailing tracks, perhaps light rail trains can inch up to the easterly sections of the terminals to provide platform level transfers.  The light rail trains need not be very high tech nor their stations.  How about some surplus equipment from Europe?  Just thinking out loud folks.
Tramway Null(0).

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