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Remote Data Sources Background

Remote Data Sources Background

Remote Data Sources Background


ENVI supports the following servers as remote data sources:

Jagwire

The Jagwire product, available from Harris 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. The Jagwire property you can edit is Formats, which is a drop-down list containing the values provided by the server. Select the value from the drop-down list.

Geodatabases

A geodatabase is a data storage mechanism that allows for many types and sources of geographic data, both raster and vector, to be supported in a consistent manner. ENVI supports reading and writing to personal geodatabases (in Microsoft Access .mdb format), file geodatabases, and enterprise geodatabases. Properties are not available for editing. ArcGIS® mosaic datasets are opened as geodatabase raster files.

OGC Servers

The Open Geospatial Consortium (OGC) provides a variety of protocol specifications for transmitting geospatial data via the web. ENVI supports two of these specifications: WMS and WCS.

OGC servers have several common features:

  • 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 (WCS only), interpolation type, pixel size, and map projection, which 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

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.

The WCS property you can edit is Formats, which is a drop-down list containing the values provided by the server. Select the value from the drop-down list.

OGC WMS

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.

The WMS properties you can edit are Formats, Spatial Reference System, Number of Columns, Number of Rows, and Map Style.

  • 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 Connection Keywords

    The OGC keywords specify details about what data to open on the server and how to open it. You specify the details by using standard keywords defined by OGC. Separate keywords from their values with an equal sign (=), and separate keyword/value pairs with an ampersand (&), for example: width=500&height=500. The following keywords are supported:

    Keyword

    Description

    WCS and WMS keywords

    format

    The format in which to transmit the data across the Internet. The format must be among the list of formats supported by the OGC server. The OGC WMS server publishes the image formats it supports, and ENVI displays a subset of image formats from the list that it supports, namely JPEG, PNG, GIF, and TIFF/GeoTIFF. If the server does not support the specified format, it is not displayed.

    Example for WMS: format=image/jpeg

    Example for WCS: format=jpg

    WCS-only keywords

    coverage

    Required. The name of the dataset. Example: coverage=srtmplus_raw

    crs

    The coordinate reference system of the image. This keyword value must be a string that comes from the list of reference systems supported by the server. Example: crs=EPSG:4326

    WMS-only keywords

    height

    The number of rows in the image when it is opened. The default for WCS is to use metadata from the image. Example: height=500

    layers

    Required. The name of the layer. You can specify multiple, comma-delimited layers. ENVI will allow the server to combine the WMS layers and display them as a single layer. Example: layers=streets

    srs

    The spatial reference system of the image. This value must be a string that comes from the list of reference systems supported by the server. Example: srs=EPSG:4326

    style

    The display style from the server-supported style list. This specifies how to display certain features, if used (for example, display a two-pixel yellow line for roads). Example: style=visual

    width

    The number of columns in the image when it is opened. The default for WCS is to use metadata from the image. Example: width=500

    JPIP and IAS Servers

    OGC and JPIP servers support delivery of image data at different resolutions that are automatically resampled by the servers. IAS and JPIP servers send compression parameters known as wavelets, while OGC servers send actual image files. This means that ENVI can read any IAS server dataset.

    Note: To view datasets from IAS and JPIP servers, you need a server that uses the ISO/IEC 15444-9 JPEG 2000 standard (JPEG 2000 Internet Protocol). IAS 3.x and higher provides support for this version of the standard.

    JPIP

    JPIP is a client-server protocol used to serve JPEG 2000 compressed imagery (.jp2, .j2c, and .jpx). The following is an example:

    jpip://exampleserver:1234/file.jp2

    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.

    IAS

    The IAS product, available from Harris Geospatial Solutions, provides a server that streams JPEG 2000 and NITF 2.1 C8 compressed imagery using the JPIP protocol for display and analysis. IAS supports full JPIP streaming capabilities, plus it provides a directory listing service, NITF support, and a tool to convert any image file to JPEG 2000 or NITF 2.1 C8 formats. ENVI does not support opening CMYK compressed JPEG 2000 files using an IAS server.

    All properties from IAS servers are read-only. The JPEG 2000 compression properties that are always available for viewing are Number of Layers, Number of Components, Number of Discard Levels, Progression, Number of Tiles, Bit Depth, and flags to indicate if the data are reversibly compressed, YCC rotated, or signed.

    • If XML boxes or UUID boxes are present in the dataset, you can select from their respective drop-down lists to view them in a separate window.
    • If NITF metadata is present in one of the XML boxes, the NITF metadata is imported if the file is opened, but only the XML data are accessible in the Remote Connection Manager’s Properties List.
    • If a GeoJP2 style UUID box is present, the map information is extracted and the following fields are added to the properties listing: Projection, Top Boundary, Left Boundary, X Pixel Size, and Y Pixel Size.

    ArcGIS Image Services Servers

    When connecting to an ArcGIS Image Services 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 Method: Choose a method for displaying a mosaic of overlapping input scenes (rasters). For details, see the ArcGIS Resources documentation. These options are only available if you have ArcGIS® for Desktop 10.5 or later installed. ENVI uses a tile-based display for imagery, so mosaics may display differently compared to ArcGIS software.
      • None: No mosaic
      • Closest to Nadir: Sort the rasters by the distance between the nadir position and view center. This is similar to the Closest to Center method but uses the nadir point to a raster, which may be different than the center, especially for oblique imagery.
      • Closest to Center: Rasters that have their centers closest to the view center are placed on top.
      • North-West: Enables raster ordering in a view-independent way, where rasters with their centers to the northwest are displayed on top.
      • Seamline: Cuts the raster using the predefined seamline shape for each raster using optional feathering along the seams and orders images based on the SOrder field in the attribute table.
    • 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 Esri® 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 Resource Center 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 Open Remote Dataset.

    Keyword

    Description

    token

    Tokens are used by ArcGIS servers to authenticate the user. For ENVI versions 5.2 Service Pack 1 and newer, tokens must be generated with the referer ENVI, or else the token will be invalid when passed into ENVI.

    Example: http://exampleserver:1234/arcgis/rest/services/folder_name/dataset_name/ImageServer/catalog_ID



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