VectorToFeatureCount Task

This task converts vector records into a feature counting layer.

Example

This example opens a shapefile of U.S. cities. It groups the 3,500 records into 50 different features by state. It creates an ENVI feature counting file (.efc) in the directory specified by the Temporary Directory ENVI preference. The default locations are as follows:

Windows: C:\Users\<username>\AppData\Local\Temp
Linux: /usr/local/tmp

After running this example, select File > Open from the ENVI main menu bar and select the output .efc file. When the Data Selection dialog prompts you to choose the associated raster, select natural_earth_shaded_relief.jp2 and click OK. ENVI creates a feature counting layer and displays it over the shaded relief image. It opens the Feature Counting Tool so that you can view the attributes of the feature counting layer.

; Start the application

e = ENVI()

; Open an input raster

File = Filepath('natural_earth_shaded_relief.jp2', $

Subdir=['data'], Root_Dir=e.Root_Dir)

Raster = e.OpenRaster(File)

; Open a point shapefile of world cities

VectorFile = Filepath('cities.shp', $

Subdir=['classic','data','vector'], $

Root_Dir=e.Root_Dir)

Vector = e.OpenVector(VectorFile)

; Get the task from the catalog of ENVITasks

Task = ENVITask('VectorToFeatureCount')

; Define input properties

Task.INPUT_RASTER = Raster

Task.INPUT_VECTOR = Vector

Task.ATTRIBUTE_FEATURE_NAME = 'ST'

Task.ATTRIBUTE_DESCRIPTION_NAME = 'AREANAME'

; Run the task

Task.Execute

; Display the shaded relief image

View = e.GetView()

Layer = View.CreateLayer(Raster)

View.Zoom, 0.3

View.GoToLocation, 4901, 2845, DATA=Layer

; Get the location of the output feature

; count file

Print, 'Feature count file created. You can manually open it from ENVI now. File location:'

Print, Task.OUTPUT_FEATURE_COUNT_URI

See More Examples.

Syntax

Result = ENVITask('VectorToFeatureCount')

Input properties (Set, Get): ATTRIBUTE_ACQUISITION_NAME, ATTRIBUTE_DESCRIPTION_NAME, ATTRIBUTE_FEATURE_NAME, INPUT_RASTER, INPUT_VECTOR, OUTPUT_FEATURE_COUNT_URI

Output properties (Get only): OUTPUT_FEATURE_COUNT

Properties marked as "Set" are those that you can set to specific values. You can also retrieve their current values any time. Properties marked as "Get" are those whose values you can retrieve but not set.

Methods

This task inherits the following methods from ENVITask:

Properties

This task inherits the following properties from ENVITask:

COMMUTE_ON_DOWNSAMPLE

ATTRIBUTE_ACQUISITION_NAME (optional)

Specify the attribute name of the column containing the acquisition time.

ATTRIBUTE_DESCRIPTION_NAME (optional)

Specify the attribute name of the column containing the description.

ATTRIBUTE_FEATURE_NAME (optional)

Specify the attribute name of the column containing the feature class.

INPUT_RASTER (required)

Specify the input raster.

INPUT_VECTOR (required)

Specify the input vector. This can be any vector format that ENVI supports. For polylines and polygons, the centroid is used to create the feature counting locations.

OUTPUT_FEATURE_COUNT

This is a reference to the output feature count file (.efc).

OUTPUT_FEATURE_COUNT_URI (optional)

Specify a string with the fully-qualified path and filename for OUTPUT_FEATURE_COUNT.

More Examples

This example downloads OpenStreetMap^® vectors of highways and roads that intersect with the geographic extent of a QuickBird image. It groups the shapefile records into features based on the type of road; for example, "residential" or "motorway."

; Start the application

e = ENVI()

; Open an input file

File = Filepath('qb_boulder_msi', Subdir=['data'], $

Root_Dir=e.Root_Dir)

Raster = e.OpenRaster(File)

; Download OpenStreetMap vectors of highways and roads

OSMTask = ENVITask('DownloadOSMVectors')

OSMTask.SUB_RECT=[-105.23, 39.98, -105.2, 40.01]

OSMTask.FEATURE_NAMES=['Highways and Roads']

OSMTask.VECTOR_TYPES=['Polyline']

OSMTask.Execute

; Convert the vector records to feature counts

Task = ENVITask('VectorToFeatureCount')

Task.INPUT_RASTER = Raster

Task.INPUT_VECTOR = OSMTask.OUTPUT_VECTOR

Task.ATTRIBUTE_FEATURE_NAME = 'highway'

Task.ATTRIBUTE_DESCRIPTION_NAME = 'name'