Remote Data Sources Background
ENVI supports the following servers as remote data sources:
OGC Servers
The Open Geospatial Consortium (OGC) provides a variety of protocol specifications for transmitting geospatial data via the web. ENVI supports these specifications: WCS, WFS, WMS, and WMTS.
OGC servers have several common features:
- For WCS, WMS, and WMTS, data are sent as image files. The supported formats are PNG, GIF, JPEG, and TIFF/GeoTIFF formats. If a dataset you are querying cannot be transmitted in one of these formats, you cannot open the dataset.
- You can customize data delivery by specifying a spatial extent, interpolation type, pixel size, and map projection. This saves you from reading unwanted data for regions you are not interested in. ENVI can manage the details of server requests, such as downloading data tiles, deleting temporary files, and reading data.
OGC WCS
Web Coverage Service (WCS) is a protocol for serving raster data that represent properties of geographic locations. WCS servers provide coverages that you can manipulate. The servers list datasets at one level instead of in a folder hierarchy.
ENVI currently supports the following WCS versions: 1.0.0, 1.1.0, 1.1.1, 1.1.2, 2.0.1. ENVI has been tested against the following WCS servers: GeoServer, ArcGIS, MapServer. WCS version 1.0.0 has the broadest and most consistent support among the various servers. With versions 1.1.x and 2.0.1, the servers implemented the specifications with their own particularities. If this causes issues, you have the option to downgrade the WCS version for better results.
OGC WFS
Web Feature Service (WFS) is a protocol for serving geographic vector feature data. ENVI currently supports WFS versions 1.1 and 2.0. ENVI has been tested against the following WFS servers: GeoServer, ArcGIS, MapServer.
You can edit the following WFS properties:
- Spatial Reference System: If additional spatial references are available, choose one from the drop-down list provided.
- Start Index: Specify an index number for the initial feature you want to download.
- Count Limit: Specify the maximum number of features to download.
- Use View Extents: Set this property to True to use the current ENVI view as the bounding box for downloading data. Only features that exist in that bounding box will be retrieved from the server. Otherwise, set it to False to get all available data.
OGC WMS
Web Mapping Service (WMS) is a protocol for serving maps that are generated on-the-fly for display purposes only. ENVI currently supports WMS version 1.3.0. A powerful feature of WMS servers is that you can identify multiple datasets that meet your criteria, and the server combines them into one displayable map layer. WMS servers do not specify a pixel size for a given dataset, so ENVI estimates a default pixel size, width, and height. WMS servers list datasets on the server in a folder hierarchy.
You can edit the following WMS properties:
- Formats, Spatial Reference System, and Map Style are drop-down lists containing the values provided by the server. Select the value from the drop-down list.
- Number of Columns and Number of Rows are derived from the layer data. You can manually edit these values to modify the resolution of the dataset to open.
- The image opens at its full geographic extent. To change the extent, create a raster subset of the original image.
When you select multiple WMS layers to open, the properties that appear are a subset of the properties available for a single WMS dataset. The multi-WMS properties you can edit are Formats, Spatial Reference System, Number of Columns, and Number of Rows.
- Formats and Spatial Reference System drop-down lists contain all of the options common to all of the selected datasets. Select the value from the drop-down list.
- The Number of Columns and Number of Rows values default to value of the first dataset you selected in the Remote Connection Manager.
Some WMS datasets contain legends to help interpret the data; legends are automatically displayed in the Layer Manager.
OGC WMTS
Web Map Tile Service (WMTS) is a protocol for serving pre-rendered, georeferenced map tiles. As you zoom in or out of a dataset, WMTS loads only the tiles you need for the given spatial extent. ENVI supports WMTS version 1.0.0. ENVI has been tested against the following WMTS servers: GeoServer, ArcGIS, MapServer.
The WMTS properties you can edit are Formats, Spatial Reference System, and Map Style. These are drop-down lists that contain the values provided by the server. Select the value from the drop-down list.
WMTS does not support multispectral images, only RGB datasets with optional alpha channels.
ArcGIS Image Services
When connecting to an ArcGIS Server, you can edit the following properties:
- Image Format: Choose from JPEG, TIFF, or PNG.
- Compression Quality: Percentage of compression to apply (0 to 100); smaller values decrease image quality, and higher values increase image quality but may increase loading time.
- Mosaic Operator: The overlapping areas will contain the cells as follows:
- First: The first raster dataset listed in the source.
- Last: The last raster dataset listed in the source.
- Min: The minimum cell values from all the overlapping cells.
- Max: The maximum cell values from all the overlapping cells.
- Mean: The mean cell values from all the overlapping cells.
- Blend: A blend of the cell values that overlap. This blend value relies on an algorithm that is weight based and dependent on the distance from the cells to the edge within the overlapping area. Use this setting when using the Seamline mosaic method.
- Ascending: If set to True, qualified mosaic datasets are displayed in an ascending order if you select a Mosaic Method above. This is similar to using the First option for Mosaic Operator.
- Coordinate Reference System: The default coordinate system. If you display an image (which sets the base coordinate system of the display) before opening an ArcGIS image service through the Remote Connection Manager, the image service request will use the same coordinate system; you cannot change it in this case.
See the ArcGIS Server documentation for more information on image services.
ArcGIS Image Services Connection Keyword
The ArcGIS Image Services token keyword is supported when connecting to an ArcGIS server in the Remote Connection Manager, or when opening an image service in the Open Remote Dataset dialog.
|
Keyword |
Description |
|---|---|
|
token |
Tokens are used by ArcGIS servers to authenticate the user. For ENVI versions 5.2.1 and newer, tokens must be generated with the referer Example: |
JPIP Servers
JPEG 2000 Internet Protocol (JPIP) is a client-server protocol used to serve JPEG 2000 compressed imagery (.jp2, .j2c, and .jpx). The Open Remote Dataset dialog is the only way to connect to a JPIP server in ENVI. If a dataset from a JPIP server contains map information, it is stored in the file header using a GeoJP2A protocol. ENVI will attempt to read and import map information and apply it to the input file whenever possible. Raw JPIP servers cannot display properties for editing.
Jagwire Servers
The Jagwire product, available from NV5 Geospatial Solutions, provides a server that streams imagery and video for display and analysis. You can remotely connect to Jagwire and open raster data that represents properties of geographic locations. Jagwire servers provide coverages that you can manipulate. The servers list datasets at one level instead of in a folder hierarchy. The images open with the native coordinate system and pixel size, and the default interpolation type is used.
You can edit the Formats property if needed.
See Also
Remote Connection Manager, Using the Open Remote Dataset Dialog, ENVI::OpenRaster