What's Up With All the Different GIS Data Formats?(And most importantly, Can I keep using Shapefiles?! Short answer: Yes.)But there are new GIS data formats that you’ll probably want to know about. If you’re using ArcGIS, at some point you’ll want to convert your data to the geodatabase (either Enterprise or File). Don’t worry – using geodatabase data is very very similar to using Shapefiles. You can start off using your data the same way you’ve used Shapefiles. Then when you’re comfortable, you can experiment with some of the advanced features that the geodatabase offers. The Personal Geodatabase The Personal Geodatabase was the new data format that ESRI created with the release of ArcGIS. Domains Personal Geodatabases have some cool features. One of my favorites is domains. Basically what domains do is tell the database that in a certain field only certain values can be entered. Say you have a dataset you are using to collect field data about asthma rates in a neighborhood. And in one column you want to collect whether anyone in the household has asthma or not. You could set the domain to be Yes or No and also set the fact that the field could not be left blank (not accept null values). Once you’ve set up a domain, the Data Entry becomes a selection from a dropdown menu rather than typing a value. That way you get a clean dataset without typos or extra notes or anything like that that an inexperienced data collector might accidentally try to enter. Feature Linked Annotation Geodatabases have the ability to create feature-linked annotation that is updated along with a feature. The New File Geodatabase ESRI plans to replace Personal Geodatabases with something called the File Geodatabase with version 9.2 of ArcGIS. So if you haven’t started working with Personal Geodatabases yet, I recommend waiting until the File Geodatabase has been released and seems stable (talk to colleagues and read the postings on the ESRI Support site to get a feel for this). That said, converting between data formats is quite easy. If you have been using the Personal Geodatabase, converting to the File Geodatabase will be a simple copy/paste update in ArcCatalog. If you are moving from Shapefiles to the Geodatabase, converting should be pretty straightforward as well. The File Geodatabase hasn’t come out yet, the version of it that I saw in an ESRI demo looked like a Shapefile or a Coverage, with multiple associated files stored on a drive, but should have the same features (domains, subtypes & feature-linked annotation) of the Personal Geodatabase. You might be thinking “But I just got used to the Personal Geodatabase, now I have to change again?! Why?!” Apparently the File Geodatabase addresses the speed issues that many of us experienced with geoprocessing on Personal Geodatabases. The File Geodatabase also will not have the 2 GB limitation of the Personal Geodatabase; the ESRI website lists the limit for the File Geodatabase as one terabyte. SDE Data – The Enterprise Geodatabase Many larger organizations are using something called SDE (ESRI’s Spatial Database Engine). SDE is basically middleware that sits between a large Oracle or SQL Server and ArcGIS and provides tools and features for the management of large spatial databases. Centrally Located Data Centrally located data is a big reason for using SDE. In large organizations where multiple departments or divisions are using GIS, Shapefiles can get out of control pretty quick. The problem with this is that sometimes people end up using out of date or incorrect data because there is not a centrally located place where edits are made. SDE fixes this. Storing Large Raster Datasets SDE also allows organizations to store large raster datasets (like Orthophotos) in seamless datasets in an efficient way that speed up drawing significantly. What this means is that you don’t have to add image tiles one at a time to your map or even worry about creating image catalogs. Multiple Editors working on a Dataset at the Same Time Another advantage of SDE is the ability to have a versioned data layer that can be edited by multiple people at the same time. This is a big bonus for large companies (a good example is the utility industry) that have the resources to manage the versioned edits. However, you’re not going to see this implemented too often at places with limited staff because of the time and complexity of managing versioned data. In general, SDE, the databases and the skills that go along with it are expensive so you’re not likely to need to use it or worry about it if you tend to work for smaller organizations. But it’s good to know what is anyway, because it’s something you’ll continue hearing about in the industry and you may see it listed on a job posting you’re interested in. Working with SDE data in ArcMap or ArcToolbox is very similar to working with any other kind of data (Shapefiles and Coverages). Managing SDE data however, can quite a learning curve. I would definitely recommend formal training if this becomes part of your job description. So How Long Can I Stick with my Shapefiles? That’s a hard question to answer. If you work for an organization that does not require you to make the switch to the geodatabase, you can continue to enjoy the simplicity/comfort factor of using Shapefiles. In addition, you may find that the organizations/departments you get data from are still putting their data out there in Shapefile format and you may not want to spend your time converting this data. However, while you can still use Shapefiles in ArcGIS, ESRI is not designing new features for Shapefiles. As an ESRI rep put it at the SERUG (Southeastern Regional Users Group) Conference, “If you’re still working with Shapefiles, you are going against the grain of the way we are designing ArcGIS.” That said, it really depends on which features of ArcGIS you want to use. If you don’t do a lot of data editing, you may be fine to keep using your Shapefiles until ESRI really truly stops supporting them. It’s hard to say when that will be. I recommend using the data format that makes the most sense to you now, but experiment with the new File Geodatabase when ArcGIS 9.2 is released to learn about the new features that are available. |
Email to a Friend