[GIS] statistical test to calculate difference/similarity between two sets of lat/lng data points

latitude longitudespatial statistics

I have two sets of data points where each data point is a latitude-longitude combination. The two sets represent two different time frames, let's say 2010-2014 and 2015-2018. The number of data points within the first time frame does not equal the number of data points in the second time frame. The data points are also independent, meaning that there exists no mapping from time frame 1 to time frame 2.

I would like to know if there exists a statistical test to compare the two sets of data points and see if the data points have shifted in geographical location, or stayed the same?

For instance, let's say the bulk of data points from 2010-2014 lies within the US, and within time frame 2015-2018 the majority of points is still in the US but also in Canada. Can we statistically say something about the shifting spatial characteristics of the two time frames.

I have tried figuring out a way to do this (PySAL for Python) but I seem to be lost.

Best Answer

You can calculate the average point of data-set A and the average point of data-set B and then take the distance between the two points to see if your points are shifting.

Calculating the Statistical dispersion of your points would tell you if your points are getting closer to each other or farther apart

Related Solutions

[GIS] How to test spatial correlation between two point layers

Since your point pattern is serial in nature, I would recommend a Kulldorff Spatial Scan Statistic using a Bernoulli model. This is a type of point pattern statistic that does not assume an homogenious point process and is inherently multiscale.

Sorry to say that this is not available in ArcGIS. Fortunately, the software SatScan has Binomial and Poisson likelihood scan statistics available (and is even GUI driven).

If you would like to go the R route take a look at the "kulldorff" function in the "SpatialEpi" package.

[GIS] How to determine vector between two lat/lon points

What you're looking for is the initial bearing (or forward azimuth), which if followed in a straight line along a great-circle arc will take you from the start point to the end point.

Here is some simple JavaScript from this link:

var y = Math.sin(dLon) * Math.cos(lat2);
var x = Math.cos(lat1)*Math.sin(lat2) -
        Math.sin(lat1)*Math.cos(lat2)*Math.cos(dLon);
var brng = Math.atan2(y, x).toDeg();

The above link has a wealth of useful information beyond this for related calculations.

As your question states, this is the simplest method - since the Earth is not a true sphere this calculation will not be 100% accurate, but it is a close approximation.

Best Answer

Related Solutions

[GIS] How to test spatial correlation between two point layers

[GIS] How to determine vector between two lat/lon points

Related Question