“The Living Atlas of the World brings ready-to-use data to the ArcGIS Platform creating a complete global Geographic Information System.”
That sounds good, doesn’t it? *But what does it mean?
It means the Living Atlas isn’t just for making web maps. The Living Atlas includes hundreds of image services you can use in ArcGIS Desktop as inputs to geoprocessing tools. That means no downloading, no data preparation, and huge time savings. Image services work so well in ArcGIS Desktop, you will be challenged to find how they differ from the raster datasets on your hard drive. However, there are some important keys to success we think worth sharing.
Why map projections matter when working with Image Server Layers
As with all GIS projects map projections matter when working with image services. By default most services deliver data projected in the Web Mercator Auxiliary Sphere coordinate system to match common web mapping applications such as the ArcGIS.com Map Viewer. While useful for visualization in web maps, Web Mercator is a poor choice for analysis due to distortions of area, distance, and shape.
To ensure that the results of analyses using image services are accurate, data in the Living Atlas is stored on the server using the original coordinate system. Starting an analysis with the original coordinate system avoids errors introduced by projecting the data.
Making the Connection and Setting the Projection*
What Not to Do.
There are two steps to using image services in ArcMap:
The ArcGIS Resources web pages provide the basic instructions for making a server connection.
To determine the URL to use to connect to the server find the layer in ArcGIS Online and then scroll down the item page to the Map Contents section:
The ArcGIS Online Item page shows the URL for the server in the Map Content’s section. You only need the circled portion
Select and copy the left portion of the url through arcgis. For example the URL for this server is “http:/landscape7.arcgis.com/arcgis/”.
Using the Make Image Server Layer Tool
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That sounds good, doesn’t it? *But what does it mean?
It means the Living Atlas isn’t just for making web maps. The Living Atlas includes hundreds of image services you can use in ArcGIS Desktop as inputs to geoprocessing tools. That means no downloading, no data preparation, and huge time savings. Image services work so well in ArcGIS Desktop, you will be challenged to find how they differ from the raster datasets on your hard drive. However, there are some important keys to success we think worth sharing.
Why map projections matter when working with Image Server Layers
As with all GIS projects map projections matter when working with image services. By default most services deliver data projected in the Web Mercator Auxiliary Sphere coordinate system to match common web mapping applications such as the ArcGIS.com Map Viewer. While useful for visualization in web maps, Web Mercator is a poor choice for analysis due to distortions of area, distance, and shape.
To ensure that the results of analyses using image services are accurate, data in the Living Atlas is stored on the server using the original coordinate system. Starting an analysis with the original coordinate system avoids errors introduced by projecting the data.
Making the Connection and Setting the Projection*
What Not to Do.There are two steps to using image services in ArcMap:
- Create a server connection in ArcCatalog.
- Use the Make Image Server Layer tool in ArcMap to create your layer
The ArcGIS Resources web pages provide the basic instructions for making a server connection.
To determine the URL to use to connect to the server find the layer in ArcGIS Online and then scroll down the item page to the Map Contents section:
The ArcGIS Online Item page shows the URL for the server in the Map Content’s section. You only need the circled portionSelect and copy the left portion of the url through arcgis. For example the URL for this server is “http:/landscape7.arcgis.com/arcgis/”.
Using the Make Image Server Layer Tool
- In ArcMap, open the Make Image Server Layer tool. Click the Open button to the right of the Input Image Service entry, and browse to the GIS Servers node, expand it, and expand the node for the server with the service you want to use. Select that service.
- Edit the output layer’s name.
- Note the cell size is set by default for you. This is still referring to the Web Mercator units.
- To set the projection, open the Geoprocessing Environments, expand the Output Coordinates section and choose the Output Coordinate System you need the server to use when providing data to your layer.
- Optionally, expand the Processing Extent section and choose a snap raster if appropriate.
- Optionally, expand the Raster Storage section and change the Pyramid resampling technique and the Resample settings. This depends on the nature of the raster data in the service (discrete versus continuous or real numbers versus categories). Projecting can radically distort or change the distribution of cell values due to if the wrong resampling method is selected—some testing may be required to be certain.
- Optionally, in the Raster Storage section, change the cell size. Use this setting rather than the setting in the tool.
- Close the Environment settings window.
- Optionally, you may find it valuable to limit the extent of the raster layer to just your study area. Do so using the Template Extent option (not the Geoprocessing Environment setting for processing extent). This helps geoprocessing performance because only the minimum amount of data is transferred from the image service.
- Click OK to run the tool.
- To verify you got the correct result, open the new Layer’s properties and on the Source tab, check the Spatial Reference property. It should be what you chose in step 4.
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