I added a layer from the web via publicly available map server in my ArcGIS Online Web Map. The data source I'm pulling from is FEMA's National Flood Hazard dataset. Its map service is here: https://hazards.fema.gov/gis/nfhl/rest/services/public/NFHL/MapServer
Now that I have this layer in my map, I'd like to limit the extent in which it appears. This layer covers the entire contiguous 48 states of the US and I really just need it for one county.
Is there a way to limit the extent, either in my Web Map, or via Web App Builder?
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More information about the layer would be helpful. If there are corresponding attributes for the county like a FIPS code, you can set a filter in the web map.jcarlson– jcarlson2021年05月30日 18:58:21 +00:00Commented May 30, 2021 at 18:58
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I've added a little more info on the data in the question - it's the National Flood Hazard Layer from FEMA. Within this dataset are multiple layers. As far as I have seen, the extents don't correspond with county boundaries and don't have county-specific attributes like a FIPS code. So I don't think filtering by an attribute that identified the county would get me where I'd like to go. I think I'm looking for something more akin to clipping based on the extent of the county or putting bounding extents into the parameters for these layers somehow.Neil– Neil2021年06月01日 13:28:18 +00:00Commented Jun 1, 2021 at 13:28
1 Answer 1
You've got a couple of ways to address this.
If you really don't want things outside of your county to display, download the NFHL, clip the data to your county, then publish your own service.
In Web App Builder, you can also customize you app's display scales. While this does not limit the rendering of the layers, it can at least keep the map at the county scale or below.
Also, if using the newer map viewer and apps based on the ArcGIS JS 4.x API is an option, you can use layer blending to act as a mask. Here's an imagery layer and my county's "County Area" polygon. The polygon is being rendered with the blend style "Destination In". Note that layers higher than the county polygon, such as the reference labels, are not affected. Layers below it appear "clipped".
Also, I want to point out that the NFHL there is a Map Image, so it's rendering the map's extent wherever you pan to. It doesn't have the same feature-level access that other layers do, and cannot be spatially limited in the same way.
As a final alternative, consider using Esri's Living Atlas layer of flood zones. It is a feature layer, and can be filtered. Just identify your county's DFIRM ID and set the filter accordingly.
If you need other layers, like the FIRM panels, then you're out of luck with this approach.
