One of the most common resources on ArcGIS OnLine are Web Maps and Map Services. While these datasets can be quite useful in composing maps, you’ll see that analyses with these data services are limited. The differences between Web Maps and Map Services are subtle and will be shown in exercises below.
Adding map service data to your map
- Open a new blank map in ArcMap.
- Open the Add Data from ArcGIS Online… box. (No sign-on is required for this exercise…)
- Search for “owner:nccgia parcel”
- View the details for NC OneMap – Parcels. Note that it is a Map Service layer.
- Add the map service layer to your map.
- Open the group layer’s properties and note the Source properties.
- Open the properties of one of the sub layers and note you have very limited functionality with these data
Map Service data are pulled directly from a server on the cloud. While they may look like normal vector datasets, they are actually images. As you zoom in or out of your map, a request is sent to the hosting server to generate a new snapshot of the data and return it to display your map. On most – but not all – map service data, you can query the data using the identity tool () to show attributes of a given feature. However, you cannot select specific attributes either by attribute or spatially.
Using web map services
- Select ArcGIS Online from the File menu (this won’t work from the “Add data” option).
- Search for “owner:NCDOT.GOV type:web”.
- View the details for “NCDOT Traffic Information Map”. Note that it is indeed a web map service.
- Click “Open”. It will ask you whether you want to save your existing map as this service is an entire new map document.
- View the properties of the various layers within the map; what can you do with these layers?
- Note in particular, the cache properties of the World_Topo_map layer, what the options are and where the cache is saved.
- Open up the ArcCatalog panel in your map and navigate to the home folder. Note where the map document has been saved.
Web map services, in contrast to map services, comprise of an entire map with links to on-line data resources. The map, and in some cases a cache of image data, are downloaded and stored on your disk. You can add data to and otherwise manipulate these maps, but often the data that come with web maps services are as limited as map service data. Though, as you’ll notice with the TIMS_Cameras layer, you can modify the symbology and query the data. That is because this layer is a feature service layer, which we will talk about in the next tutorial.