what is geodatabase and why is it different from shapefile?

[nunupodi]

Hi there,

i am new to gis, and i would like to learn more about it. Now I get confuse what are the differences between geodatabase and shapefile. And if we have geodatabase, do we need to convert it into shapefile so that we can use it as a layer? Please advice.


Looking forward for nice people to explain.

Thanks

[VinceAngelo]

Geodatabases and shapefiles are two different storage formats for spatial data. Shapefiles
were originally created in the 1990s for use with the original ArcView. They use the dBase-III
format to store attributes, and are subject to many limitations (among them: lack of numeric
nulls, very short column names, day resolution dates, and short ASCII strings). "Geodatabase"
is not a single format, but a family of formats that take advantage of true database concepts
and support a wider range of datatypes, NULL columns, and raster datatypes. All modern
Esri GIS applications can directly read geodatabases; not many others do. There's probably
several hundred pages of documentation which touch on your topic, but if you start with
something like A quick tour of data management, you'll have a good beginning.


- V

[nunupodi]

thanks vangelo. So, what are the condition that we need to create geodatabase instead of using shapefile.

[VinceAngelo]

Shapefiles are larger, slower, and less flexible than file geodatabases. Most importantly, they
are "lossy" (what you get out isn't what you put in -- truncating column names, restricting
string fields to 254 characters, no international character support, poor resolution on dates,
"zeroification" of NULL numeric values,...). I can't think of one reason to use shapefiles when
a file geodatabase is an option.

- V

[AlexeyTereshenkov]

Agreed with Vince.

You would want to use personal or file geodatabases (which depends on your business workflows) whenever possible. However, keep in mind that non-Esri applications are not aware of file geodatabase format since it is essentially an encrypted folder (unless you want to work with File GDB API - http://resources.arcgis.com/content/geodatabases/10.0/file-gdb-api).
Personal geodatabases can be accessed by non-Esri software that "understands" MS Access database format (of course we are talking about tables and not geographic datasets).
That is why you would want to use shapefiles - this is an open format which you can work with in various software (http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf). This is the reason why, for example, largest data vendors like Navteq and TomTom deliver their datasets in shapefile format.

[VinceAngelo]

Just one note to add on the "personal geodatabase" format -- Esri has deprecated support for
Access-based geodatabases. 64-bit ArcGIS Server 10.1 will not support this format. Desktop
will support it for a bit longer, but if you're just starting out, there isn't much good in heading
down a known cul-de-sac with a sign stating "Dead End."

- V

[DerekLaw]

Hi Nunu,

Just to add onto what others have posted, you may want to listen to this podcast:
An Overview of the Geodatabase and Five Reasons Why You Should Use It

It's available from here: Esri Instructional Series Podcasts
(do a filter for Geodatabase)

Hope this helps,