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Problem: Identify results for WMS features differ from expected

Description

When you use the Identify tool to query a WMS service feature, the results in the Identify results dialog may be different than expected.

1. Results are not displayed in the usual tabular grid.
[O-Image] identify_results
2. Using the <Top-most Layer> option, doesn't work as expected. The result is empty.

3. Using the <All layers> option, doesn't work as expected. The tree view includes all WMS service sublayers even if there are no features present at the point of identification.
[O-Image] identify_noresults
4. The result for a particular WMS service sublayers is empty.

Note:
WMS Features have no primary display field. The WMS feature in the left pane tree view will always be refered to as 'WMS Feature(s)'.

** The feature addressed in this article is only available in ArcGIS 9.0 Service Pack 2, which can be downloaded through the link in Related Information, below. **

Cause

1. Identify results for WMS services are displayed using an Internet Explorer control embedded in the Identify window.

This is because identify results returned by a WMS service can be in any of several formats, such as field/value pairs, HTML or an image.

The Identify window will display whatever is returned from the service.

2. When you use the <Top-most Layer> option the Identify Tool will only identify features from the top-most sublayer in the WMS service's drawing hierarchy. A result will be returned even if there are no features present for this sublayer.

3 & 4. At version 1.1.1 the WMS specification does not provide any tags or formats that help ArcMap determine whether there are features to identify at that location or not. Therefore, <All layers> will return results for all WMS service sublayers and there will be a result even if there is no feature present for a particular sublayer.

Solution or Workaround

1. This is a known limitation.

2, 3 & 4. These are known limitations. We recommend that you either use the <Visible layers> option, which will identify features in any of the visible layers in the WMS service layer, or to select the particular layer you are interested in identifying.

Related Information