OgrDataSet Class
A dataset that reads various vector data formats, via the OGR Simple Features Library.
NuGet/Assembly: Carmenta.Engine.5.16.2.nupkg (in the CEDataSets assembly)
Syntax
public class OgrDataSet : MultiFileDataSet,
IReadAttributes,
ISearchableRemarks
This dataset reads vector data via the OGR Simple Features Library, which originally was a separate library but is nowadays an integrated part of the GDAL library (Geospatial Data Abstraction Library). The GDAL library is an open-source library providing read (and sometimes write) access to a variety of file formats and some other types of data sources. This dataset does not use all the features of the library. Please see Acknowledgments for copyright information.
Vector Formats Included in the Carmenta Engine GDAL/OGR Build
Note that Carmenta does not have access to test data for all formats listed below and that we therefore cannot guarantee that they will work as expected in Carmenta Engine.
Format name | OGR code | Alternative reader in Carmenta Engine |
|---|---|---|
ARC/Info Binary Coverage | AVCBin | |
Atlas BNA | BNA | |
Comma Separated Values | CSV | |
Epi Info .rec | REC | |
ESRI Personal GeoDatabase | PGeo | |
ESRI Shapefile | ESRI Shapefile | |
GeoJSON | GeoJSON | |
GML | GML | |
GMT | GMT | |
GPX | GPX | |
KML | KML | |
Mapinfo File | Mapinfo File | |
Microstation DGN | DGN | |
ODBC | ODBC | |
OGR Virtual Format (Virtual Datasource) | VRT | |
ESRI FileGDB | FileGDB | |
S-57 (ENC) | S57 | |
SDTS | SDTS | |
UK .NTF | UK .NTF | |
U.S. Census TIGERLine | TIGER |
These formats should be documented as GDAL Vector Drivers. In addition, you can find some information on MapInfo files below.
OGR layers
Some data formats, for instance S-57, may be read by the OGR library as several separate layers. If a feature is read from a layer with a defined name, the layer name will be set as the attribute "layer" on the feature. If a feature does not belong to a named layer, the attribute will not be set.
It is possible to read only features from a specific OGR layer, by attaching an OgrQuery to the ReadOperator.
MapInfo files
A MapInfo TAB file may reference a raster file instead of Mapinfo vector data. In this case, the OgrDataSet automatically tries to create a raster dataset to read the file, and all queries are forwarded to this internal dataset. Supported raster formats are MrSID and ECW, plus formats supported by the GdalDataSet.
Important information regarding ECW: To handle references to these raster files, the OGR plug-in is linked to the ECW, MrSID and GDAL plug-ins. This could cause a problem if the ECW runtime files are not installed, in which case the OGR plug-in will fail to load. Please see the EcwDataSet for more information about how to install the ECW runtime files.
The MapInfo vector format is unusual in containing not only semantic attributes ("this line is a railroad") but also visualization data ("this line should appear as a brown dashed line"). The OGR library supports reading of such visualization data from MapInfo files (TAB and MIFMID formats). The OGR dataset reads this information and adds it as attributes to the generated features. There are four different groups of attributes: pen, brush, symbol and label attributes. But the OgrDataSet does not add visualizers to the features, so if you want to display them as MapInfo would do it, you have to use a VisualizationOperator with the proper visualizers that use these attributes. The attribute values have been set so they can be used directly by the visualizers; for instance all color attributes are strings on the format "rgba(r,g,b,a)".
Nevertheless, it is cumbersome to create visualizers to ensure that, for example, a line feature with the attributes
mapinfo_pen: 30 pen_color: "rgba(0,0,255,255)" pen_unit: #pixels pen_width: 1.0 pen_outer_width: 3.0
will appear as
 |
So Carmenta has prepared visualizers in advance, in a template configuration file. The template contains a layer with four different VisualizerSet instances you can use for visualizing texts, symbols, lines and polygons, called MapInfoTextVisualizers, MapInfoSymbolVisualizers, MapInfoLineVisualizers and MapInfoPolygonVisualizers. You might copy the entire layer to your own configuration file, but we recommend a slightly difference procedure, which will make it easier to upgrade to future versions of the template file:
Copy the template file samples/MapInfo/MapInfoTemplate.px to your own folder of configuration files. This file contains a lot of visualizers, but you only need to access the four top-level visualizer sets. To use one of these in a your own configuration file, you should create a reference to the VisualizerSet in the copy of the template. (That is: open both files in Carmenta Studio, make them half-sized so that both files are visible, then use the right mouse button to drag one of the four top-level VisualizerSet instances from your copy of the template file, and drop it on the VisualizationOperator in your other file. Then choose Create Reference Here, and then choose visualizers.)
If the original MapInfoTemplate.px is improved in future versions of Carmenta Engine, this will not automatically improve your application, since your references are pointing to your copy of MapInfoTemplate.px. To use the improvements, you should update your copy manually, but you will not have to modify any other files.
Note that not all visualization data in MapInfo files can be read. Most noticeably, reading symbols from external image files or TrueType or OpenType fonts is not supported. Label organizing information and some font styles are also discarded. Here is the full list of visualization attributes that may be set for MapInfo files:
Attribute name | Description |
|---|---|
pen_color | Color to draw lines or polygon outlines in. |
pen_unit | Length unit for the pen_width attribute. |
pen_width | The line width. |
pen_outer_width | Depending on the line style, it might be necessary to draw the line in two passes (using two different visualizers with different colors). This property specifies the width of the wider line drawn at the bottom to create an outline. |
ogr_pen | An integer attribute between 0 and 8, indicating the line style. Please see the OGR feature style specification for the meaning of these values. Note that for MapInfo files, there is also a format-specific "mapinfo_pen" attribute, which might be used instead. |
mapinfo_pen | Only set for MapInfo files. The value is an integer indicating the MapInfo line style. |
brush_forecolor | Color to draw a solid polygon in, or the foreground color for a patterned polygon. |
brush_backcolor | Color to draw the background in for a patterned polygon. |
ogr_brush | An integer attribute between 0 and 7, indicating a fill pattern for the polygon. Please see the OGR feature style specification for the meaning of these values. Note that for MapInfo files, there is also a format-specific "mapinfo_brush" attribute, which might be used instead. |
mapinfo_brush | Only set for MapInfo files. The value is an integer indicating the MapInfo fill pattern. |
symbol_color | Color to draw the symbol in. |
symbol_unit | Length unit for the symbol size and offsets. |
symbol_size | Actual symbol size, in pixels or Crs units, depending on the symbol_unit attribute. This value is not adjusted for the size of the symbol used on the SymbolVisualizer. Since this symbol is probably larger than 1 by 1 pixel, you must use a PointVisualizerSet to scale the symbol down accordingly. |
symbol_angle | Specified the symbol rotation in degrees, clockwise from north. |
symbol_offsetx | Horizontal offset. |
symbol_offsety | Vertical offset. |
ogr_symbol | An integer attribute between 0 and 10, indicating which symbol to draw. Please see the OGR feature style specification for the meaning of these values. Note that for MapInfo files, there is also a format-specific "mapinfo_symbol" attribute, which might be used instead. |
mapinfo_symbol | Only set for MapInfo files. The value is an integer indicating the MapInfo symbol to use. |
label_text | The text string to draw. |
label_forecolor | Color to draw the label in. |
label_backcolor | Color to draw the text background or halo. |
label_font | The font to use for drawing labels. This also specifies the size of the text. |
label_unit | Length unit, specifies how the font size is interpreted. |
label_angle | Specified the label rotation in degrees, clockwise from north. |
label_placement_mode | TBD. |
label_align_x | One of the AlignX values. |
label_align_y | One of the AlignY values. |
label_offset_x | Horizontal offset. |
label_offset_y | Vertical offset. |
Inheritance Hierarchy
System.Object (not available in C#)
EngineObject
ResourceObject
DataSet
FileDataSet
MultiFileDataSet
OgrDataSet
Platforms
Windows, Linux, Android
OgrDataSet Members
The OgrDataSet type has the following members.
Constructors
| Name | Description |
|---|---|
| OgrDataSet | Initializes a new instance of the OgrDataSet class. |
Properties
| Name | Description |
|---|---|
| IReadAttributes.Attributes | Gets a collection whose contents determine which attributes will be read the DataSet. Inherited from IReadAttributes |
| CodePage | Gets or sets the code page to use for string attributes. |
| Crs | Gets or sets the coordinate reference system of the OgrDataSet. Inherited from DataSet |
| DatumShiftChoice | Gets or sets a flag that tells how to choose a default datum shift for the Crs. |
| Description | Gets or sets a short description of the dataset. Inherited from DataSet |
| DisplayName | Gets or sets a display name for the dataset. Inherited from DataSet |
| FileName | Gets or sets the name of the file to read from. Inherited from FileDataSet |
| ISearchable.HasSearchIndex | Gets a value that tells whether a dataset has a search index. Inherited from ISearchable |
| Id | Gets a unique identifier for this dataset instance. Inherited from DataSet |
| IndexFileName | Gets or sets an explicit index file name used for the generated index files in IndexPath. Inherited from MultiFileDataSet |
| IndexPath | Gets or sets the directory where the dataset index files are saved. Inherited from MultiFileDataSet |
| IsDisposed | Gets a value that tells whether the current OgrDataSet has been disposed. Inherited from EngineObject |
| IsoMetadataDocument | Gets or sets the path to an ISO 19139 metadata document for the dataset. Inherited from DataSet |
| Name | Gets or sets the name of the OgrDataSet. Inherited from ResourceObject |
| NativeHandle | Gets the native Carmenta Engine kernel object the current OgrDataSet represents. Inherited from EngineObject |
| OverrideAttributes | Gets or sets attributes that will override the style attributes read from MapInfo TAB files. |
| Path | Gets or sets the path to the file or files to read from. Inherited from FileDataSet |
| IReadAttributes.ReadAttributes | Gets or sets a value indicating whether the DataSet reads attributes. Inherited from IReadAttributes |
| SearchableAttributes | The attributes that will be used to create a search index for the dataset. |
| SearchableCondition | Gets or sets a condition that determines which features will be included in the search index for the dataset. |
| SearchSubdirectories | Gets or sets a flag indicating if the dataset will search for data files recursively. Inherited from MultiFileDataSet |
| SuppressInitializationErrors | Gets or sets a flag indicating how errors during dataset initialization are handled. Inherited from DataSet |
| IUserProperties.UserProperties | Gets the AttributeSet that contains the user properties. Inherited from IUserProperties |
| VerifyIndexFiles | Gets or sets a flag indicating if the contents of index files should be verified before use. Inherited from MultiFileDataSet |
Methods
| Name | Description |
|---|---|
| Clone | Creates a copy of an object. Inherited from EngineObject |
| Dispose | Releases the reference to the native Carmenta Engine kernel instance the EngineObject represents. Inherited from EngineObject |
| Equals | Determines whether this instance is equal to another. Inherited from EngineObject |
| FindChildObject | Overloaded. Finds the child object with the specified name. Inherited from DataSet |
| FlushCache | Frees any information the dataset may have cached, including all cached features. Inherited from DataSet |
| GetChildObjects | Overloaded. Gets the child objects of the current object. Inherited from DataSet |
| GetDataCoverage | Gets coverage information for this dataset in a given area. Inherited from DataSet |
 GetDataSetById | Looks up an existing dataset instance from a dataset identity. Inherited from DataSet |
| GetDataSetInfo | Returns a dataset info that describes the contents of this dataset. Inherited from DataSet |
| GetDataSetInfoAsync | Makes an asynchronous call to GetDataSetInfo. Inherited from DataSet |
| GetFeature | Gets the feature with the specified identity. Inherited from DataSet |
| GetFeatures | Overloaded. Gets features from the dataset. Inherited from DataSet |
| GetFloatValueAt | Overloaded. Gets the float raster value from a cell at the specified position. Inherited from DataSet |
| GetFloatValuesAt | Overloaded. Gets a number of float raster values. Inherited from DataSet |
| GetLocalizedDescription | Gets a localized version of the dataset description in a specific language. Inherited from DataSet |
| GetLocalizedDisplayName | Gets a localized version of the dataset display name in a specific language. Inherited from DataSet |
| GetLocalizedIsoMetadataDocument | Gets the path to an ISO 19139 metadata document for a specific language. Inherited from DataSet |
| GetNormalizedFloatValueAt | Overloaded. Gets the raster value from a cell at the specified position, normalized by Scale and Offset. Inherited from DataSet |
| GetNormalizedFloatValuesAt | Overloaded. Gets a number of raster values, normalized by Scale and Offset. Inherited from DataSet |
| GetValueAt | Overloaded. Gets the integer value from a raster cell at the specified position. Inherited from DataSet |
| GetValuesAt | Overloaded. Gets a number of raster values. Inherited from DataSet |
| HasLocalizedDescription | Checks if a localized version of the dataset description is available in a specific language. Inherited from DataSet |
| HasLocalizedDisplayName | Checks if a localized version of the dataset display name is available in a specific language. Inherited from DataSet |
| HasLocalizedIsoMetadataDocument | Checks if an ISO 19139 metadata document is available for a specific language. Inherited from DataSet |
| HighestRasterValue | Finds the highest raster value inside the given polygon. Inherited from DataSet |
| Initialize | Initializes the dataset. Inherited from DataSet |
| ISearchable.Search | Overloaded. Searches for features with an attribute whose value match the specified search text. Inherited from ISearchable |
| SetLocalizedDescription | Sets a dataset description in a specific language. Inherited from DataSet |
| SetLocalizedDisplayName | Sets a dataset display name in a specific language. Inherited from DataSet |
| SetLocalizedIsoMetadataDocument | Sets the path to an ISO 19139 metadata document for the dataset, for a specific language. Inherited from DataSet |
| TryGetFloatValueAt | Overloaded. Gets the float value from a raster cell at the specified position. Inherited from DataSet |
| TryGetNormalizedFloatValueAt | Overloaded. Gets the float value from a raster cell at the specified position, normalized by Scale and Offset. Inherited from DataSet |
| TryGetValueAt | Overloaded. Gets the integer value from a raster cell at the specified position. Inherited from DataSet |