Understanding and calculating distances between points using lat/lon

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10-31-2016 03:03 PM
Yi-JyunLin
New Contributor II

Hello, I do not have a geometric background, but I have a research project requires me to calculate distances between, say, a conflict site and the nearest major city (with population more than 1000000). I wonder are there any good sources can help me understand how to calculate this distance and how this is done by ArcGIS (explain the formula used to calculate the distance in a simple way). Besides, are there any good source for illustrating how grid and centroid points are generated (and the math) in ArcGIS?

Thanks!

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2 Replies
DarrenWiens2
MVP Honored Contributor

This is a surprisingly complicated question. The short answer is that ArcGIS can calculate distances in several different ways depending on things like which tool you use and which projection (if any) your dataset(s) are in, and it will calculate the distance how you tell it to do so.

As a starting point, here is a blog post comparing geodesic to euclidean distances (both of which can be computed in ArcGIS), but there are many, many resources out there devoted to this topic.

Also, see this link, which will you start you on your journey through the help pages:

How proximity tools calculate distance—Help | ArcGIS for Desktop 

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TedKowal
Regular Contributor II

A down and dirty way:

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwjG67W84YfQAhVGyyYKHRwKDS4... 

Use the formula in the excel sheet ....  "Note this is only a very rough approximation!"  Lat long is highly dependent upon the curvature of the earth which varies from location to location"

A more complex way answering your question would be to write a script that determines the shortest distance to a point representing a cities that have been filtered to meet your requirements

In scripting this ... look at the material Darren Wiens‌ gave and Generate Near Table—Help | ArcGIS for Desktop 

A set of tools from SpatialEcology  (Donation Ware)  I highly encourage support if you find them useful!  Has tools that will assist in finding distance between two points.... GME | SpatialEcology.Com 

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