thomas.nies_noaa

How to Measure Distances Between Points?

Discussion created by thomas.nies_noaa on Apr 16, 2010
I am running Arcview 9.3.1 with spatial analyst.

I have two point datasets that I want to compare. The points represent observations on specific events  - in this case, a series of individual trips, with each trip having a unique identifier, or TRIPID. The two datasets are of the same group of trips but represent the postions as reported to two different data systems. One dataset has one position for each trip, while the other has multiple positions for each trip.

What I want to do - for each individual trip - is determine the difference between the single reported position and the multiple positions. While ideally I would like to get summary statistics for each trip (like the average, maximum, and minimum difference), I'd be happy if I could get a table that listed the differences between the single point and the multiple points for each trip which could then be analyzed outside of ArcMap. There are a large number of trips and data points so  splitting the tables to represent single trips is not really an option.

All the scripts I've found seem to want to match every point to every other point, rather than only match points for individual trips. Hawth's Geospatial Modelling Environment can be made to work using a "for" loop, but produces a separate output file for each trip which then has to be edited and combined (see command line example below) for analyzing the overall patterns.

Any suggestions? Thanks in advance.




Here is the GME command line I tested for four individual trips. In this case I combined the two datasets into one table.

for (i in 1:4)
{ pointdistances(in="[all_one]", fld="record", out=paste("test9",i), format="SUMMARY",where=paste("Tripid=",i,));};

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