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I am a college student using ArcEditor 10.0 for a semester project measuring distance to hospitals from census tract centroids. This is my first time using ArcGIS, and I have no formal training. So this question may be very simple, but is it possible to calculate distance between two different types of points between two layers? In one layer I have a shapefile for census tracts and I've calculated the centroids. In the other layer I have geocoded hospital addresses. I would like to calculate distance from each census tract centroid to the nearest hospital. Is there a tool in Arc Toolbox that will do this/could you give a brief overview of the tool?

Thank you!

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2 Answers 2

Since you have ArcInfo, you can use the Near geoprocessing tool to find the distance. It's in ArcToolbox > Analysis > Proximity. Your input features will be Census tract centroids and your near features will be hospitals.

You may want to consider running the analysis simply on the Census tract polygons instead of their centroids. Tracts are large and often very odd-shaped, especially in rural areas. If you use centroids, you can end up with weird-looking results if elongated panhandles are close to a hospital but that tract's centroid is still far.

Moreover, you may also want to consider using a higher spatial resolution Census geography, e.g. block groups or blocks. American Community Survey data are available down to the block group resolution, and would probably produce better looking results.

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In Arc10, the Near command is actually located in the ArcToolbox > Analysis > PROXIMITY toolset, but agree that this is the tool you want to use, and only available with an ArcInfo license. –  RyanDalton Nov 8 '11 at 16:21
    
Oops, my mistake. Thanks for the correction! –  dmahr Nov 8 '11 at 18:56
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Sorry, I always get the licenses confused...I actually have ArcEditor, not ArcInfo, which doesn't have the Near tool. Is there anyway to do a similar analysis in ArcEditor? –  Stephanie Nov 8 '11 at 22:44
    
Yes, you can do a similar analysis if you relax your requirement to use a tool: the capability is built right into the software and is instantly available with a right-click. Unfortunately, the "Add Join" tool--which ought to do the job--does not seem to support this functionality. –  whuber Nov 8 '11 at 22:51

Perform a spatial join. Make sure the two layers are first projected appropriately, because the distance will be computed using the Pythagorean Theorem (not using spherical geometry). To access it, right-click on the target layer name in the TOC, choose "Joins and Relates," and fill out the dialog like this (where "CITIES" is the source layers), paying attention to option 2:

Screen shot

A new dataset will be created and added to the TOC. It has one record for each of the original records in the target layer. The last field in its attribute table contains the computed distance to the nearest source feature.

(This capability, which is part of the base ArcView functionality and therefore needs no special licensing (unlike Near) has been part of ArcView since version 2; only the interface and output format have changed.)

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Gosh I hate spatial joins (slowest darn thing), but I agree that this is the tool for the job. –  Nathanus Nov 8 '11 at 22:56
    
They're not slow with good software :-). Being suspicious, before replying I tested the join illustrated: it attempts to join 3000+ cities to 40,000+ zip codes. It took around 10 seconds (3.2 GHz Xeon, loads of RAM etc). That's fast enough for student work. For practical applications, I have had scaling problems in recent versions of ArcGIS, especially with extremely large source datasets, so do some initial testing before committing to this (or any) solution. –  whuber Nov 8 '11 at 22:59
    
With my setups, I'm typically joining a couple dozen million X to a few hundred thousand Y, so my computer just checks out for indeterminate amounts of time. I suppose that shouldn't be any surprise, though. –  Nathanus Nov 8 '11 at 23:08
    
@whuber Thank you for the help! I'm pretty sure my data is a in a geographic coordinate system (GCS_North_American_1983). How can I change to a Cartesian system? –  Stephanie Nov 8 '11 at 23:28
    
And what is the distance unit of measurement/how would I change units? –  Stephanie Nov 8 '11 at 23:47

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