PNT2CHIP

Description

PNT2CHIP extracts chips from a geocoded image using a point layer.

Parameters

Name	Type	Length	Value range
Input: Geocoded image *	Raster port	1 - 1
InputPoints: Point layer *	Vector port	1 - 1
InputDEM: Elevation layer	Raster port	0 - 1
Background value in geocoded layer	Integer	0 - 3
Chip ID Field	String	0 -	Default: ShapeID
Chip database *	String	1 -
Chip sensor type	String	0 - 1
Chip acquisition date (ddmmmyyyy)	String	0 - 1
Chip size (pixels,lines)	Integer	0 - 2	Default: 64
Background value in elevation layer	Float	0 - 1

* Required parameter

Parameter descriptions

Input: Geocoded image

Specifies the input geocoded layers from which to extract chips.

InputPoints: Point layer

Specifies the input point layer for which chips will be collected. One chip will be created centered about each point in the point layer.

InputDEM: Elevation layer

Optionally specifies the input elevation layer to provide the height information for each extracted chip.

When no DEM is provided, the elevation of the chip will be assigned the elevation of the point from which the chip was created.

Background value in geocoded layer

Optionally specifies the background (NoData) value of the geocoded file. If this parameter is not specified, the BACKVAL value will be set from the NO_DATA_VALUE metadata tag.

All pixels are considered valid values if BACKVAL is not set.

Chip ID Field

Specifies a field name in the input vector segment that will be used as Chip IDs - unique identifiers for the generated chips. If no field is specified, ShapeID is used by default.

Chip database

Specifies the name of the chip database to receive the extracted chips.

If the specified database already exists, new chips are appended to it. If it does not already exist, the function creates a new chip database file (.cdb).

Chip sensor type

Optionally specifies the name of the sensor for the geocoded image. This is a free format that can be used later to select appropriate chips.

Chip acquisition date (ddmmmyyyy)

Optionally specifies the acquisition date of the geocoded file.

A regular expression for chip dates (ddmmmyyyy) is acceptable; for example, "01may2012". This parameter may be used later to select chips that match an appropriate time period.

Chip size (pixels,lines)

Optionally specifies the size of each extracted chip, in pixels and lines. The default size is 64 x 64.

Because this parameter accepts up to two values, rectangular chips can be extracted. When only one value is provided, square chips result. The maximum size for each side of the square or rectangle in 1024.

Background value in elevation layer

Optionally specifies the background elevation (NoData) value in the DEM elevation channel. If one of the provided points falls on a pixel with this value, that point is ignored.

If the output DEM file (FILEDEM) is specified and this parameter is not, the BACKELEV value will be set from the NO_DATA_VALUE metadata tag.

All pixels are considered valid elevation values if BACKELEV is not set.

Details

PNT2CHIP extracts image chips from a geocoded file to a chip database, based on an input point vector layer. The extracted chips are stored in a chip database, which can be used for future image tie-down or automatic geocoding.

The projection of the point vector layer can be different than that of the geocoded file. If the projections are different, the point locations are projected on-the-fly to the projection of the geocoded image.

If background (NoData) values exist in the geocoded image, you must specify this value using the BACKVAL (Background data value in geocoded layer) parameter. Chips with background values are ignored.

You may specify a chip sensor and date for the geocoded file; these values can be used later in automatic geocoding to select chips that match the appropriate information.

PNT2CHIP will assign the vector layer point ShapeID as the image chip ID.

To perform orthorectification in a future process, you must extract the elevation of the chip by specifying a digital elevation model file (FILEDEM) with an elevation channel.