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RAD Web Mapping Services Help and FAQs
Overview
The EPA Office of Water has made available several Web Mapping Services that contain nearly all of the NHD-based WATERS Program data, plus other WATERS-related layers. The services are available for use from the EPA's intranet and internet environments. This purpose of this help page is to describe the contents and purpose of each of the RAD IMS Services, and to provide 'how to' information for both general users and application developers.
The RAD Services are provided as ArcIMS Feature and Image services that utilize web/xml technology to enable the display and query of spatial RAD Event data. Both types of services are accessed through the use of ESRI's Arc Extensible Markup Language (AXL). Non-developers can utilize these services using mapping applications that 'speak' AXL, such as ArcMap or ArcExplorer. Using these tools, the RAD ArcIMS Services can be used as a data source, transparently integrated with other data sources such as shapefiles or SDE layers.
For developers, custom html-based web applications can be created that use standard AXL syntax to make requests for data and process the returned AXL data string to display maps or other information. The primary function of the RAD ArcIMS Image Services is to create and return images that are defined by the AXL <GETIMAGE> request. These images (typically .jpg or .png format) can then be displayed in the web application. The feature service also utilizes AXL requests and responses, but instead of creating an image, it streams AXL feature descriptions, which can then be mapped by the client. The feature service requires the use of a Java-based client.
The RAD image and feature services are also provided as OGC WMS and WFS web mapping services. WMS and WFS allow developers to create client mapping applications using open source projects or commercial software that connects to OGC compliant sources. For more information please see http://www.opengeospatial.org.
Service Descriptions
There are 29 RAD Services: 3 main servics, 13 image services and 13 feature services. The primary product of the RAD Image Services is a .jpg image depicting the RAD data requested. A description of each service is provided below.
RADImageDetailed - this service provides a comprehensive collection of WATERS-related data, with detailed thematic symbology that aligns with EnviroMapper for Water symbology.
RADImageBasic - this service is similar in content to the RADImageDetailed service, but does not contain the level of detailed thematic layer symbology. This enhances drawing performance and provides a smaller, simpler legend. This service is appropriate for users who do not need the detailed symbology, or for developers who may be assigning their own symbology definitions.
RADFeatureDetailed - this service is identical in content to the other services, but returns streamed vector features rather than a graphic. One major benefit of this is that the RADFeature layers can be incorporated into ArcMap or ArcExplorer sessions without 'overlap' issues associated with Image services. The RADFeature layers behave similarly to other SDE or shapefile layers within ArcMap. These layers can easily be individually symbolized and classified and incorporated with the rest of the layers.
Image/Feature subsets The services have been separated into specific individual services for ease of use and to reduce service latency. Please refer to the individual programs for detailed information.
- RAD_evt_303d_image - this service provides impaired waters maps.
- RAD_evt_303d_feature - this service provides impaired waters feature data.
- RAD_evt_305b_image - this service provides assessed waters maps.
- RAD_evt_305b_feature - this service provides assessed waters feature data.
- RAD_evt_beach_image - this service provides beaches maps.
- RAD_evt_beach_feature - this service provides beaches feature data.
- RAD_evt_cso_image - this service provides combined sewer overflow maps.
- RAD_evt_cso_feature - this service provides combined sewer overflow feature data.
- RAD_evt_cwns_image - this service provides clean water needs maps.
- RAD_evt_cwns_feature - this service provides clean water needs feature data.
- RAD_evt_fish_image - this service provides fish maps.
- RAD_evt_fish_feature - this service provides fish feature data.
- RAD_evt_grts_image - this service provides nonpoint source project maps.
- RAD_evt_grts_feature - this service provides nonpoint source project feature data.
- RAD_evt_ndz_image - this service provides sewage no-discharge zones map.
- RAD_evt_ndz_feature - this service provides sewage no-discharge zones feature data.
- RAD_evt_pcs_image - this service provides facilities that discharge to water maps.
- RAD_evt_pcs_feature - this service provides facilities that discharge to water feature data.
- RAD_evt_tmdl_image - this service provides total maximum daily load maps.
- RAD_evt_tmdl_feature - this service provides total maximum daily load feature data.
- RAD_evt_wqs_image - this service provides water quality standards maps.
- RAD_evt_wqs_feature - this service provides water quality standards feature data.
- RADEventLayers_image - this service provides all of the event programs maps.
- RADEventLayers_feature - this service provides all of the event programs feature data.
- NHDLayers_image - this service provides all of the NHDLayers maps.
- NHDLayers_feature - this service provides all of the NHDLayers feature data.
The table below lists all of the layers available in the RAD IMS services, and the raw SDE source table that the layer is derived from.
How To Access the RAD IMS Services from ESRI desktop software (ArcExplorer, ArcGIS, ArcView)
Accessing the RAD IMS Image Services from ESRI
desktop
software is straightforward. In any of the above-mentioned applications
- Select
the 'Add Layer' button
- Select
'WWW Server' from the list of options
- The
address for the IMS Web Services is: http://epamap32.epa.gov
- Select
the 'Specific Service' option and select one of the image or feature
services
- Once you see the service name listed to the right, highlight it and press the 'add' button
This service and all of its available layers are now loaded into your mapping application.
If the layers in the services are scale dependent, you may not see all the layers listed in the table of content (TOC) in the map window. If you cannot see the layers you are interested in, you probably need to zoom in or zoom out until the layers' legends become active in the TOC. Once the layers become active, select the layers to display them in the map window. You may also need to scroll down TOC panel to see all the layer names.
When drawing a large number of layers, or a layer with large number of features, you may need to wait for several seconds to get the layers drawn in the map window. After the layers are selected to draw, a green flashing light in the upper-left corner of the TOC indicates that the application server is working to generate a new map. Once loaded, individual layers can be turned 'on' or 'off' by checking or unchecking the checkboxes at the left of the layer names in the TOC.
Unlike an image service, each individual layer in a feature service is added separately into the ArcGIS Desktop application after the service is selected. Another advantage of the feature service is that you can customize the symbology of each map layer.
These services can be used in conjunction with data from other sources (including local data sources). However, in that case, symbology conflicts may exist, and filled polygon layers may hide other layers; these issues will have to be assessed and solved by the user on a case-by-case basis.
Dynamic Integration of RAD IMS Services
A useful feature of ArcIMS services is that they can be accessed through a URL, which facilitates dynamic integration of the ArcIMS service into a web page. For example, if a specific geographic area needs to be monitored periodically, a URL can be built defining its bounding box, including all the layers of interest and pointing to the URL to the RAD IMS services. Then the URL can be integrated into a web page as a pop-up map window. Every time the link with the URL is clicked, a map is dynamically generated and drawn in the pop-up window.
General Information/FAQs
What is the RAD?
The RAD is the EPA Office of Water Reach Address Database. It houses the EPA Office of Water geospatial data as well as the National Hydrography Dataset (NHD) data, and several other related geospatial layers. There are 2 copies of the RAD, both located at the EPA Computing Center at RTP. One copy serves the EPA internet applications and does not contain any data considered secure or sensitive. The second copy serves the EPA intranet applications and users.
What is an ArcIMS Map Service?
An ArcIMS Map Service is a web-hosted application that accepts requests for maps and data and returns corresponding results. The language used for all requests and results is ArcXML (Arc Extensible Markup Language), a specific implementation of XML (eXtensible Markup Language).
Is an ArcIMS service the same as a 'Web Service'?
Not exactly. ArcIMS services are accessed through the web by submitting and receiving AXL (Arc eXtensible markup Language) to a web-hosted ArcIMS application server Though they utilize XML these ArcIMS services do not qualify as 'true' web services because they do not support SOAP, WSDL, and are not registered on UDDI. Want to know more about true web services, including what all of those acronyms stand for? See the W3C web site at: http://www.w3.org/
Is this the same service used by EnviroMapper for Water?
No. EnviroMapper uses an older technology (Map Objects Internet Map Server) web mapping service. The EnviroMapper map services are not available for use outside of EnviroMapper. The ArcIMS RAD services have been designed to closely mimic the EnviroMapper services in content, feature naming conventions, and symbology.
Why can't I see all the layers in the RAD IMS Services?
The map layers available in the RAD IMS Services can be extremely large. For example, an attempt to draw all of the NHD Waterbodies at the national scale/level may fail because it contains too many features to render, which may cause the web server to time out. Not to mention, even if the features do draw, they would be so dense that virtually nothing would be discernable on the map. The same situation occurs in EnviroMapper, which only permits the layers with a big number of features to be drawn when zoomed in to the 'state' or 'local' scale. The RAD IMS Services use a similar approach to set 'scale thresholds' for each layer. These scale dependencies will not permit a layer to display until the map is zoomed in to the point where the scale threshold is crossed. If a layer is not visible, keep zooming in until the layer becomes active in the TOC. (Note: you may have to scroll down the TOC to see all of the available layers). Once the layer is available in the TOC, you can click the check box to turn it 'on' if it isn't already checked. If you still don't see any of that layer's features on the map, it is because there are no features in the part of the country that you are viewing.
The RAD IMS Scale Thresholds are designed to match the "National", "Regional", "State", and "Local" thresholds set in EnviroMapper for Water. Labels are also associated with scale dependent layers. The more you zoom in, the more labeled features will be visible.
Why are there 'Empty' Layers available in the RAD IMS Services?
Each RAD program layer feature type is really comprised of three logical layers: 'points', 'linear', and 'area'. To be sure that you are viewing all of the data for a program layer, all three feature types need to be turned on. Some RAD programs may not have data for all three feature types, but however, the non-existent feature types have also been added to the RAD IMS Services as empty layers being the place holders so that as soon as the data is available the features will be automatically available to map.