Convert Polygons to Points in ArcGIS

During analysis it is important to keep various techniques at hand as the data sometime requires creative thinking to carry out certain tasks in a feasible way.  One of these techniques to have handy is the ability to convert polygons to points.

In ArcInfo there is a tool that allows this to be done.

ArcToolBox –>Data Management Tools –>Features –>Feature to Point

However, if you have a lower license, there is a simple workaround.  (The headings are links to specific demonstrations of these steps.)

Calculate Lat/Long for Shapefile

1. Add X and Y fields to your polygon attribute table

2. Calculate the X and Y coordinates

3. Export the attribute table to a new *.dbf

Create Point File from XY Data

4. Add new table to map document

5. Add XY event layer

6. Export temporary XY event layer file to permanent file

Geocoding – Guide to Address Locating in ArcMap

Geocoding is a process that enables you to match database records to a real world location based upon attribute fields such as addresses, PINs, Cities, etc.  Carrying out this process in ArcMap is very simple and can be completed in just a few steps.

Note: This example uses addresses, but other attributes can be used.

1. Compile Address Table – This can be done in excel, access, or other compatible file format .

Read more on: Excel in ArcGIS Desktop

2. Create Address Locator – The address locator will be based upon the data that needs to be located and the reference data.

• Open ArcCatalog
• Open desired folder for Locator to be saved in
• Right click in contents area
• Click New -> Address Locator…

3. Choose Locator Style – This will depend upon the source data and reference data.  These data types need to correlate.

4. Set Address Locator Options

• Name and Description
• Reference data – The data you will match to such as address points, streets, or city points.
• Match corresponding fields – This will vary by locator style.  US Streets is shown here.
• Set Matching Options – You will find which configuration works best through trial and error.
• Click Ok

Your locator has now been create and is shown in ArcCatalog via the “House” icon.

5. Add Address Table to Map – You can add Excel tables directly into ArcMap (9.2 or later) or create a .dbf table to be added in.

6. Right Click Table -> Geocode Addresses…

7. Add  Locator to Map and Select it to be Used – You will need to browse to the folder (via the “Add..” button) that contains the created locator.

8. Complete Locator/Geocoding  Options

• Select Corresponding Input Fields
• Choose Output Location
• Click Ok

Status is updated during geocoding process and results are shown on map.

10. You can Review or Rematch Any Address

• Right Click on geocoded point file in Table of Contents
• Data -> Review/Rematch ddresses…
• Follow options in Interactive Rematch Dialog

CAD to GIS Shapefile

CAD files are created with extreme detail, but how can you use them in GIS?  These files do not work quite like GIS feature classes or shapefiles in spatial analysis.  They can be converted to a usable format through a few basic steps.

1. Add CAD file to ArcMap
2. Select by Attribute desired layers
3. Export selected features to shapefile or feature class
4. Add new layer to map

You can also use ArcToolbox to convert from CAD

1. ArcToolbox -> Conversion Tools -> Import From CAD
2. Select Input CAD File
3. Input New Geodatabase Name
4. Select Coordinate System (optional)
5. Click Ok

Here is a video for further demonstration.

Note: Videos are broadcast through youtube.com.  Some browsers may block this content.

ESRI also has some good courses for working with CAD files in GIS on their training website.

Related Readings

KarelCAD provide inputs on CAD and Geographical Information Systems

“What is spatial design, and how can it be applied to sustainability problems?”

What – There is a Better AutoCAD!?

Import From CAD and Chainsaws

ArcGIS Geodatabase Benefits

I was just recently doing a spatial join between a polygon shapefile and a point feature class file.  There were approximately 400 polygons and 38,000 points.   There were several fields within the point file which were being summarized based upon which polygon they fell within.  The entire join process took about an hour.  I then took the output file, which was a geodatabase polygon feature class and joined it to a similar point file.  Amazingly, that join process only took 5 minutes.

This is just one example of the efficiency of the Geodatabase.  Geoprocessing is so much quicker.  A savings of time is a savings of money.  Here are a few other things to know about the various types of geodatabases.

Personal Geodatabase

• Single User Editing
• Stored in Access Database File
• 2 GB Max Size

File Geodatabase (ArcGIS 9.2+)

• Single User Editing
• Stored in a Folder
• Efficient Data Structure for Increased Performance
• 1 TB per Table Max Size

SDE Geodatabase

• Multiuser Editing
• Disconnected Editing
• Stored in a RDBMS

Additionally, with the geodatabase you can create:

Topologies
Geometric Networks
Feature Linked Annotation
Relationship Classes
Sub Types and Domains
A Centralized location for all the geographic data

So with these benefits of the geodatabase, try converting some of your data.  Creating a geodatabase does not take long as you can find out in my 90 Second Geodatabase post.  Also, ESRI has a great blog post entitled: Migrating your existing data into the Geodatabase.  It goes into great detail into how to import the following file types into the geodatabase.

• Shapefiles
• Coverages
• CAD
• Tables
• Imagery

Try out the geodatabase today, you will find many benefits.  If it seems a little awkward, give it time as you will get adjusted to the concept.  There is nothing to loose.  If you don’t like it then delete the geodatabase and go back to using your shapefiles.

Good Luck!

Related Website Pages

File Format Support in GeoCommons – Do Geodatabases Make Sense?

Five reasons why you should be using the File Geodatabase

Related Books

Designing Geodatabases: Case Studies in GIS Data Modeling

Modeling Our World: The ESRI Guide to Geodatabase Design

Calculate Lat/Long for Shapefile

Ever needed to add XY or Latitude/Longitude values to you shapefiles or feature classes?  Well, what seems to be a mystery can easily be done with just a few clicks.

The easiest way to get the lat/long values is to right click the field and select “Calculate Geometry…”. You can define whether to calculate x or y along with other geometries too.

Here is a more extensive video tutorial.

Read more

Create Point File from XY Data

Collecting X and Y coordinates are becoming easier and easier with all of the new GPS technology.  Getting the collected data into GIS can be done without adding each point by hand.  Here is a simple tutorial on creating a point shapefile from a table with XY coordinates.

Note: Videos are broadcast through youtube.com.  Some browsers may block this content.

90 Second File Geodatabase

Recently my professor challenged our class to create File Geodatabase in under 90 seconds.  For those who are new to ArcGIS, this can seem like a steep challenge.  Once you get the key steps down, it will come second nature.  These steps are important in beginning to understand how to use a geodatabase. 

Here is the test:

Setup:  Create working folder; Find Spatial Reference to Import; Find Feature Class to Import
(Clock Starts Now)
1. Create New File Geodatabase
2. Create New  Feature Dataset
3. Import Feature Class
(Clock Stops When Import Ends)

Solution:
1. Right Click Working Folder and Select New -> File Geodatabase (give logical name)
2. Right Click the Geodatabase and Select New -> Feature Dataset… (give logical name)
A. Give Logical Name
B. Import Spatial Reference Information
3. Right Click the Dataset and Select Import -> Feature Class…
A. Select Feature to Import
B. Name New Feature Class

So, I challenge you to see how fast you can complete this test.  Can you do it in under 90 seconds?  Post your results in the comments of this post.

The creative part of me decided that I should see if I could create a model to implement these steps.  Below is the model that I created.  This model takes about 5 seconds to create a File Geodatabase, Feature Dataset, and Import a Feature Class.