GRDPNT

Point coverage gridding


EnvironmentsPYTHON :: EASI :: MODELER
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Description


Given a set of points stored in a vector layer, generates a raster image where each gray level corresponds to the attribute value of the closest point.
Note: If vectors are not stored in PIXEL coordinates, the image georeferencing and vector georeferencing must match.
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Parameters


Name Type Caption Length Value range
FILE* String Input file name 1 - 192  
DBVS* Integer Input vector segment 1 - 1  
DBOC* Integer Output raster channel 1 - 1  
FLDNME String Field name for elevation 0 - 64 Default: ATTRIBUTE

* Required parameter
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Parameter descriptions

FILE

Specifies the name of the PCIDSK image file from which the vector segment point data is read and to which the rasterized output is written.

DBVS

Specifies the vector segment that contains point data. The vector segment may contain both point and line information; however, for the purposes of this function, only the point data and its associated attribute values are used.

DBOC

Specifies the output image channel to receive the rasterized image.

FLDNME

Specifies the field name that contains the elevation values.

If this parameter is specified as ZCOORD, the actual z-coordinates of the vectors are used. Field names are not case-sensitive, and they do not need to be specified in complete form. If more than one match exists, the first name is used.

Supported values are:

The Field Name (FLDNME) parameter is required only for vector layers that contain 3-D points or contours. For 3-D lines, the z-coordinates are automatically used. For 2-D layers, the elevation values are not specified.

The same name applies to all contour and 3-D point segments specified in the input vectors (DBVS) parameter. The segments that do not satisfy this requirement can be converted to the required format using ZVALTRNS.

If a field name other than ZCOORD is specified but is not found, VDEMINT attempts to use the z-coordinates of each vertex or point; this may, however, lead to unexpected results.

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Details

GRDPNT uses as input the point data structures within the specified vector segment (DBVS) of the input file. An output channel (DBOC) is created in which the area of any given region represents all pixels that are closer to the attribute location defining the region than to any other attribute location specified by DBVS.

If an attribute value is out of range for the output channel data type, its value is truncated to the minimum or maximum allowable value. GRDPNT tallies the number of attributes requiring truncation measures and reports this information. If all attributes were truncated, it is likely that the wrong output channel was specified. Run CDL to check the data type for the output channel (8-bit, 16-bit signed or unsigned, or 32-bit real) and run VECREP to verify that the attribute values are within the range for the output channel data type. If only a few attributes were truncated, they too can be checked as outlined; however, these are more likely to be the result of digitizing errors or special cases.

If the units for storing vector data are not "PIXEL", but are "UTM" or any other type, the image file must be georeferenced using GEOSET prior to running GRDPNT. The georeferencing units must be the same as were used in collecting the vector data. Run GEOREP to print the current georeferencing information for the image file.

Vector segments can be created using RAS2PNT, with the polygon information option set to "POINT" or "BOTH", using a thematic image as input.

Each vector may contain more than one attribute field. The FLDNME (Field Name) parameter is used to select the attribute field to use.

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Examples

Using USGS landuse/landcover channel 6 of irvine.pix as input, generate a vector segment of point information that can be used as input to run GRDPNT.

Filter the USGS landuse/landcover channel 6 to ensure that a reasonable number of points are generated.

EASI>file	=	"irvine.pix"
EASI>dbic	=	6   
EASI>dboc	=	7
EASI>flsz	=	5,5	 ! specifies a 5x5 filter size
EASI>mask	=		! process entire image
EASI>thinline	=	"OFF"	! do not preserve thin lines
EASI>keepvalu	=	
EASI>bgzero	=	''	! parameter ignored

EASI>RUN FMO

Generate a vector segment containing one point location (centroid) for each coverage (polygon) of the filtered classification image.

EASI>file	=	"irvine.pix"
EASI>dbic	=	6	! classification channel
EASI>dbsd	=	'Example'
EASI>filo	=	"irvine.pix"
EASI>ftype   =
EASI>ftoptins=
EASI>lasc	=	

EASI>RUN RAS2PNT 

Direct display of the vector segment file to the terminal. Only a portion will be displayed, as such files are generally very large.

EASI>file	=	"irvine.pix"
EASI>dbvs	=	lasc	! use last created segment from RAS2PNT 
EASI>vrtype	=	'VERT'
EASI>report	=	"TERM"

EASI>RUN VECREP

Resulting output:

 VECREP  Vector Segment Report      
 
 irvine.pix                 [S   11PIC     512P     512L] 

 33:Centroid  Type:116 [Vectors/Polygons]   
 Contents: Example
 Length:         6.0 Kbytes     Units: PIXEL        Structures: 250
 Bounds: (     0.000 X,      0.000 Y), (   512.000 X,    512.000 Y)

 Structure     1   Type: Point    Group:    0  Attribute:        21

        15.500 X,            0.500 Y
 
 Structure     2   Type: Point    Group:    0  Attribute:        32

        48.500 X,            0.500 Y
 
 Structure     3   Type: Point    Group:    0  Attribute:        32

       208.500 X,            0.500 Y

Alternatively, the vectors can be can be displayed graphically using CATALYST Professional Focus.

Generate rasterized regions using the vector point data of LASC as the seeds for growing the regions.

EASI>file	=	"irvine.pix"
EASI>dbvs	=	lasc	! use last created vector segment from RAS2PNT
EASI>dboc	=	8
EASI>fldnme	=	 ''	! default, ATTRIBUTE

EASI>RUN GRDPNT

Print a 15x15 numeric window of the raster output to the terminal.

EASI>file	=	"irvine.pix"
EASI>dbic	=	8
EASI>dbiw	=	390,490,15,15	! print window

EASI>RUN NUM
 NUM     Database Numeric Window   

 irvine.pix                 [S   11PIC     512P     512L] 
 8 [ 8U] GRDPNT  Region growing complete                 

 Offset: (     355,     490)  Size: (      15,      15)
 
          3   3   3   3   3   3   3   3   3   3   3   3   3   3   3
          5   5   5   5   6   6   6   6   6   6   6   6   6   6   7
          6   7   8   9   0   1   2   3   4   5   6   7   8   9   0
       +-----------------------------------------------------------
    491| 76  76  76  76  76  76  76  76  76  76  76  76  76  17  17
    492| 12  76  76  76  76  76  76  76  76  76  76  76  17  17  17
    493| 12  12  76  76  76  76  76  76  76  76  76  76  17  17  17
    494| 12  12  12  12  76  76  76  76  76  76  76  17  17  17  17
    495| 12  12  12  12  12  12  76  76  76  76  17  17  17  17  17
    496| 12  12  12  12  12  12  12  12  76  76  17  17  17  17  17
    497| 12  12  12  12  12  12  12  12  12  17  17  17  17  17  17
    498| 12  12  12  12  12  12  12  12  12  12  17  17  17  17  17
    499| 12  12  12  12  12  12  12  12  12  12  17  17  17  17  17
    500| 12  12  12  12  12  12  12  12  12  12  31  31  31  17  17
    501| 12  12  12  12  12  12  12  12  12  31  31  31  31  31  31
    502| 12  12  12  12  12  12  12  12  12  31  31  31  31  31  31
    503| 12  12  12  12  12  12  12  12  31  31  31  31  31  31  31
    504| 12  12  12  12  12  12  12  12  31  31  31  31  31  31  31
    505| 12  12  12  12  12  12  12  31  31  31  31  31  31  31  31

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