NC OneMap Services

Frequently Asked Questions

What are web services?
A web service is simply a method of providing functionality between two electronic devices. Using a browser to get directions to a local restaurant is an example of using a web service. Viewing imagery on Bing Maps is another example. In GIS terms, web services provide access to raster or feature (vector) data. An image service provides access to raster data (e.g. aerial orthophotography). Similarly, a map service provides access to feature data (e.g. roads, streams, public school points). These services provide more than a pretty picture. Typically, image and map services allow users to get information about individual features of the data. For example, a user viewing game land areas could click on a game land and see its name and type of game land it is (e.g. archery zone), etc. GIS data published to an image or map service can be used by desktop GIS software in much of the same way as the same data set copied to your desktop. These services can also be used with other web applications such as Google Earth.
Can I just download the data?
Of course. The purpose of NC OneMap is to support intelligent decision-making. There obviously are situations where downloading the data is necessary. You can do that by visiting the GeoSpatial Portal. However, for the majority of situations, web services provide several advantages. Web services allow you to access the most up to date data without the overhead of searching, downloading, storing, and monitoring the website for data updates. By using web services you are always ensured of accessing the most recent information. Also, users of ArcGIS desktop can have instant access to all of the web services hosted by NC OneMap by adding the NC OneMap server to ArcCatalog.
What are the various image services containing orthoimagery?
  • Orthoimagery_2017: Imagery for the 26 Eastern Piedmont counties of North Carolina. Visit the NC Orthoimagery Program website for more information.
  • Orthoimagery_2016: Imagery for the 27 Coastal counties of North Carolina. Visit the NC Orthoimagery Program website for more information.
  • Orthoimagery_2015: Imagery for the 24 Southern Piedmont and Mountain counties of North Carolina.
  • Orthoimagery_2014: Imagery for the 26 Northern Piedmont and Mountain counties of North Carolina.
  • Orthoimagery_All: All the imagery collections (1993-2015) in one image service. This service is time-enabled which allows for time-series change analysis. However, there is a tradeoff in that the performance is a bit slower than the other services due to the huge number of individual images.
  • Orthoimagery_Latest: An image service showing the latest imagery available for any given location in NC (including 2015). This is the most versatile service (supports hundreds of map projections) and is a seamless statewide coverage.
  • Orthoimagery_Latest_cached: An image service that shows the same imagery as "Orthoimagery_Latest." However this image service is cached for improved performance. Zoom levels are pre-defined and is limited to the "web mercator" projection. Best used when building custom web applications. Overlays correctly with other common web maps from Bing, Google, and Esri.
  • ortho_boundaries: A map service showing the image extents for all collections of imagery.
What image service should I use if I want to see the latest imagery?
The latest imagery for any location in NC can be seen by using either the "Orthoimagery_Latest" or "Orthoimagery_Latest_cached".
What image service should I use if I want the best performance?
While all the image services in the Imagery folder provide excellent performance (~1 second average response time), users may opt for a cached image service. The "Orthoimagery_Latest_cached" service has been cached using the industry-recognized caching levels used by Google, Bing, and Esri. This service has been cached in the web mercator projection. The "Orthoimagery_Latest_cached" service shows the latest imagery available for any given location in NC. If you need to view imagery in another projection please read the next question.
If cached services provide the best performance, why would I opt to use a non-cached service with the same data?
While cached services provide the best performance, there are other factors that you may need to consider. Cached services only provide data in the projection that was defined when creating the cache. In addition, the cached services only provide data at specific scales. Your project may require you to use a projection other than "web mercator" or view data at a scale that may be "in between" the pre-defined scales established in the cache. While some software packages have the capability to mitigate these hinderances, using the non-cached service may prove to be a better option in these scenarios.
What service should I use if I need to view in a projection other than web mercator?
Other than the "Orthoimagery_Latest_cached" service, the image and map services hosted by NC OneMap are dynamic. The map server can provide the web service contents in almost any projection. Projecting is done "on-the-fly" by the server.
How do I add services to ArcGIS for Desktop?
In the desktop ArcGIS environment, it is very easy to add all the services NC OneMap has to offer (that originate from NC OneMap servers). To do so, open ArcCatalog and under GIS Servers double-click on Add ArcGIS Server. In the Add ArcGIS Server window click on Use GIS Services and click Next. In the Server URL text box enter (no quotes) "https://services.nconemap.gov/secure/services". Click Finish (no username and password needs to be entered). In the Contents tab you will see all the services available from the NC OneMap server. All the imagery services may be viewed be expanding the "Imagery" folder.
I have ArcGIS for Desktop but I want to add a service using WCS, WFS, or WMS. How do I do that?
If you want to add a WMS or WCS service to desktop ArcGIS, click Add WMS Server (or "Add WCS Server") under GIS Servers in ArcCatalog. In the Add WMS Server window enter the URL of the NC OneMap WMS service to add in the form https://services.nconemap.gov/secure/services/Imagery/[image_service_name]/MapServer/WMSServer?", where [image_service_name] is the name of the service found on the NC OneMap Services page. Note: If adding an image service you'll need to include the folder name "Imagery", as that is where the image services are stored. As an example, for the 2012 orthoimagery image service the URL would be: https://services.nconemap.gov/secure/services/Imagery/Orthoimagery_2012/ImageServer/WMSServer?. When finished you can click Get Layers to see the data layers included in the service, or just click Ok. In the Contents tab you will see the WMS service listed. View video.
I don't have Esri ArcGIS software but rather a Computer Aided Design (CAD). Can I use map services or image services with my software?
Yes. All services found on the Services page are created in ArcGIS Server. For those whose software cannot consume an ArcGIS Server service, each is also provided in the relevant Open GIS Consortium specifications. For map services, users can access the services using either the Web Map Service (OGC WMS) or Web Feature Service (OGC WFS) specification. Image services support the OGC WMS and OGC Web Coverage Service (OGC WCS) specifications. For more information please visit http://www.opengeospatial.org/standards. The steps required to add the services using the OGC specifications will vary with the software. However, we do have videos that show how to add web map services to AutoCAD, Microstation, and Carlson. Otherwise, please refer to your software help for more information.