OS (GB) NTF Reader Parameters

FME recognizes a set of standard Ordnance Survey NTF products and provides a feature schema tailored to the data product, with field names appropriate to the data product. However, any NTF file not recognized as a targeted product profile is handled generically, at some cost to efficiency and tailoring of feature schema.

When this parameter is checked, recognized products are treated using the generic rules, rather than the product-specific rules. This may be useful if new versions of standard products are inappropriately treated by product-specific rules, or if you want all features from different products to be treated using a common, or generic, schema.

FME can read Land-Form PANORAMA™ and Land-Form PROFILE™ raster Digital Terrain Model (DTM) products, translating each pixel into a point feature. This can produce a lot of point features—160000 to 250000 per file. Sometimes it is desirable to extract only a sub-sample of the features, while maintaining a regular grid pattern of points.

This parameter specifies a decimation factor that is applied in the horizontal and vertical directions. A value of 3, for instance, returns only one in three points in both horizontal and vertical directions from the reader, resulting in an 8/9ths reduction in the total number of features.

Use this parameter to expose Format Attributes in Workbench when you create a workspace:

• In a dynamic scenario, it means these attributes can be passed to the output dataset at runtime.
• In a non-dynamic scenario where you have multiple feature types, it is convenient to expose additional attributes using this one parameter. For example, if you have ten feature types and want to expose the same attribute in each one, it is easier to define it once than it is to set each feature type individually in the workspace.

Using the minimum and maximum x and y parameters, define a bounding box that will be used to filter the input features. Only features that intersect with the bounding box are returned.

If all four coordinates of the search envelope are specified as 0, the search envelope will be disabled.

When selected, this parameter removes any portions of imported features being read that are outside the Search Envelope.

The example below illustrates the results of the Search Envelope when Clip to Search Envelope is not selected (set to No) and when it is selected (set to Yes).

• No: Any features that cross the search envelope boundary will be read, including the portion that lies outside of the boundary.
• Yes: Any features that cross the search envelope boundary will be clipped at the boundary, and only the portion that lies inside the boundary will be read. The underlying function for the Clip to Search Envelope function is an intersection; however, when Clip to Search Envelope is selected, a clipping operation is also performed in addition to the intersection.