When identifying WMS layer features, it may be difficult to obtain successful results.
1. Clicking Close to a feature may still not return a successful result.
2. Using the <Top-most layer> option unexpectedly returns empty results.
3. The results are incorrect.
** 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. **
There are a number of possible causes:
1. The success of identifying point or line features often depends on the tolerance level set, that is how many pixels can the coordinate of the Identify click be from the actual coordinates of the feature. The set tolerance may be such that a click "close" to a feature may not be close enough to return a successful result.
2. When you use the <Top-Most Layer> option the Identify Tool will only identify features from the top-most layer in the WMS service's drawing hierarchy. A result will be returned even if there are no features present.
3. Identify results for WMS layers may be incorrect if the data frame is rotated.
Solution or Workaround
The causes listed above have corresponding numbered solutions given below:
- The tolerance level is set by the WMS server and may differ in some cases. An ID click close to one WMS service's feature may give a successful result, while a similar click for a different service’s feature is not successful. This is a known limitation.
- 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, ArcMap will return a result even with an empty value.
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 select the particular layer you are interested in identifying.
- This is a known limitation.