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<html><head><title>FMEObjects Gateway</title></head><body bgcolor="#ffffff"><h1>FMEObjects Gateway</h1>Feature sources supported by FMEObjects are supported for reading by OGRif the FMEObjects gateway is configured, and if a licensed copy of FMEObjects is installed and accessable.<p>To using the FMEObjects based readers the data source name passed shouldbe the name of the FME reader to use, a colon and then the actual datasource name (ie. the filename). For instance, "NTF:F:\DATA\NTF\2144.NTF"would indicate the NTF reader should be used to read the fileThere are a number of special cases:<p><ul><li> A data source ending in .fdd will be assumed to be an "FME Datasource Definition" file which will contain the reader name, the data source name, and then a set of name/value pairs of lines for the macros suitable to pass to the createReader() call. <p><li> A datasource named PROMPT will result in prompting the user for information using the regular FME dialogs. This only works on Windows.<p><li> A datasource named "PROMPT:filename" will result in prompting, and then having the resulting definition saved to the indicate files in .fdd format. The .fdd extension will be forced on the filename. This only works on Windows.</ul>Each FME feature type will be treated as a layer through OGR, named by thefeature type. With some limitations FME coordinate systems are supported.All FME geometry types should be properly supported. FME graphical attributes(color, line width, etc) are not converted into OGR Feature Style information.<p><h2>Caching</h2>In order to enable fast access to large datasets without having toretranslate them each time they are accessed, the FMEObjects gatewaysupports a mechanism to cache features read from FME readers in "Fast Feature Stores", a native vector format for FME with a spatialindex for fast spatial searches. These cached files are kept in thedirectory indicated by the OGRFME_TMPDIR environment variable (or TMPDIR or /tmp or C:\ if that is not available). <p>The cached featur files will have the prefix FME_OLEDB_ and a master indexis kept in the file ogrfmeds.ind. To clear away the index delete all thesefiles. Do not just delete some.<p>By default features in the cache are re-read after 3600s (60 minutes). Cache rentention times can be altered at compile time by altering the fme2ogr.h include file. <p>Input from the SDE and ORACLE readers are not cached. These sources aretreated specially in a number of other ways as well.<p><h2>Caveats</h2><ol><li> Establishing an FME session is quite an expensive operation, on a 350Mhz Linux system this can be in exceess of 10s.<p><li> Old files in the feature cache are cleaned up, but only on subsequentvisits to the FMEObjects gateway code in OGR. This means that if unusedthe FMEObjects gateway will leave old cached features around indefinately.<p></ol><h2>Build/Configuration</h2>To include the FMEObjects gateway in an OGR build it is necessary to haveFME loaded on the system. The <i>--with-fme=</i><b>$FME_HOME</b> configurationswitch should be supplied to configure. The FMEObjects gateway is not explicitly linked against (it is loaded later when it may be needed) so itis practical to distribute an OGR binary build with FMEObjects support withoutdistributing FMEObjects. It will just "work" for people who have FMEObjectsin the path.<p>The FMEObjects gateway has been tested on Linux and Windows.<p><hr>More information on the FME product line, and how to purchase a license forthe FME software (enabling FMEObjects support) can be found on the Safe Software web site at <a href="http://www.safe.com/">www.safe.com</a>.Development of this driver was financially supported by Safe Software.<p></body></html>⌨️ 快捷键说明
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