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3.9. Process menu

Process Series

Purpose

Parameters

Remarks

Max

Maximum value

Min

Minimum value

Avg

Average value

Range

Range of values

Sum

Sum of values

Count

Number of valid pixels

Stddev

Standard deviation of values

Decloud

Temporal smoothing technique

Slope

Slope of trend-line of values

MaxDate

When the maximum value occurs

MinDate

When the minimum value occurs

Some of these functions require additional parameters as well.

See File-name list files for more information (§ 2.7.1.) on how to create a list of image names for this function.

Process Images Algebra

Purpose

Parameters

Remarks

This function is used to perform simple algebraic and logic functions on any number of images. It was originally created for applying correction factors to NDVI images. However, there are many other applications. For instance,


The result of a logical operation is 1 (TRUE) or 0 (FALSE). The logical operators are as follows:

>

greater than

<

less than

=

equal to

>=

greater than or equal to

<=

less than or equal to

&

and

|

or

<>

not equal to


A Equation can be any mix of variables, numbers, and operators (+, -, *, /). Numbers can be any valid integer or floating point number (ie 3.059). Variables must begin with a letter or underscore, but the rest of the variable can contain a mix of numbers, letters, or underscores. Some examples:

VARIABLES

NUMBERS

Image_1

30

month

32.083

_01234_

.000009

Once a equation has been input, WinDisp will find all the possible variable names and prompt you for a filename to tie to the variable. Note that any variable can occur as many times as you wish.

Algebra will also do string comparison. Anything placed in quotes (") Algebra will assume is a string. This can be useful in a batch file where the user may want to fix pixel results for a certain file

Example line from a BATCH FILE

would find the average of THIS_FILE and SOME_FILE if the value of the batch variable FOO is not BADIMAGE.IMG.

Process Images Compress

Purpose

Parameters

Remarks

Process Images Window

Purpose

Parameters

Remarks

Process Images Filter

Purpose

Parameters

Remarks


The filter implemented here is a simple averaging filter. For each pixel in the output image, the average of the corresponding pixel in the input image and all of its neighbors is calculated. The number of neighbors to include is determined by the filter width. A filter width of 3 will include the pixel and its eight nearest neighbors defined by a 3x3 pixel box around the pixel.

Process Images Difference

Purpose

Parameters

Remarks


For quick visual comparisons, File Open Image to display difference images on-the-fly.

Process Images New

Purpose

Parameters

Remarks

Base value is the value you want all the pixels of the new image to be initialized to. Height and Width of image are the height and width in pixels you want the image to be. If you wish to set projection and value-scaling information to the image, use Process Header Edit or Process Header Change Value.

Process Images Paste

Purpose

Parameters

Remarks

Process Images Map

Purpose

Parameters

Remarks

Process Images Mosaic

Purpose

Combine a series of images into a single image

Parameters

File list of image names
Image to create

Remarks

Join two or more images into a single image. Images must have valid projection information in the image headers. The first image in the series must be the northern-most and western-most image in the series.

See File-name list files for more information (§ 2.7.1.) on how to create a list of image names for this function.

Process Stats

Purpose

Parameters

New!!!

Remarks

Available statistics include:

Max

Maximum value

Min

Minimum value

Avg

Average value

Stddev

Standard deviation of values

Range

Range of values

Count

Number of pixels in a polygon within thresholds

For a series of points or polygons, spatial statistics for those features are extracted from a series of images and the results stored in a tabular ASCII file. The points and polygons are read in from a map file. All images in the series should have the same header window and projection parameters because the map masks (pixels to extract statistics from) are only calculated for the first image.

See File-name list files for more information on how to create a list of image names for this function.

The stats file stores the results in quote/comma-delimited ASCII format, one map feature per line, statistics from one image per column. The first row contains field names that are derived from the first column in each row of the file list. Each row starts with the feature name derived from the map file, followed by one value from each image in the file list. Up to 36 statistics (up to 255 characters total) can be stored on one line.

The extracted statistics can be viewed with any ASCII editor, spreadsheet or database application, or with the internal viewer available from File Open Table. The values from a specific column can be used to shade a map with File Open Map or File Retrieve Map. The values can be overlayed on a map with Draw Labels. Time-series graphs can be drawn with View Graph Map Data.

By default, if more than half of the polygon contains pixels outside the relevant thresholds, a value of -9999 is returned. Both the thresholds and the percentage of the polygon that needs to be valid can be modified with the Process Thresholds command.

Process Header Edit

Purpose

Parameters

Remarks

See Process Header Change Value for information on how to modify a single image header value.
See Image headers for a detailed description of the header parameters.

Process Header Change Value

Purpose

Parameters

Variable name
Variable value

Remarks

Use Process Header Edit to view and edit all header values.
See Image headers for a detailed description of the header parameters.

The following is a list of valid variable names (see § 4.1.2. for a detailled description) :

Process Threshold

Purpose

Parameters

Remarks


In a generic image, all possible pixel counts (0-255) are included in the processing functions grouped under the processing menu. For other image types, certain pixel counts are excluded from certain functions. In FEWS NDVI images, for instance, use counts 0 and 1 to store cloud masks, so the thresholds are set automatically to 2-255. The cloud pixels are excluded during processing.

IDA automatically sets default thresholds for each image type prior to processing. If the thresholds set by the THRESHOLD function are 0-0, then the defaults are used, otherwise the user-defined thresholds are used.

WARNING: Once the thresholds are set, they will be used throughout the rest of the current WinDisp session. If the thresholds are saved to the ini file, then they will be used in all successive WinDisp sessions as well. As a precaution, the thresholds should always be reset to 0-0 after processing.

When filtering a FEWS NDVI image, the user may wish to smooth only the land surfaces to avoid averaging coastlines and water together. To do this, set the thresholds to 82-255. 82 is derived from the equation COUNT = (NDVI*256)+82.

If the image type is CALCULATED, then the user can specify these values in the image header with Process Header Edit or Process Header Change Value.

Process SEDI Automatic

Purpose

Automatically calculate interpolated image

Parameters

Input SURFER data file
Background image
Positive or negative relationship (P / N)
Number of pixels extracted per station (1, 3, 5, 9, 13)
Delimiter of input SURFER data file
Missing value in input file

Distance between gridlines (kilometers)
Search radius for interpolation (kilometers)
Number of nearest stations to use
Output image file
Image type
Slope
Intercept

Remarks

This function automatically calculates all three SEDI steps.
See Process SEDI for more information.
Note that two separate commands are created when recording a batch file. Both commands must be included in the order they are created. The commands are:
Process SEDI Automatic A
Process SEDI Automatic B

Process SEDI Assisted

Purpose

Automatically calculate interpolated image using parameter defaults

Parameters

Input SURFER data file
Background image
Output image file
Missing value in input file

Remarks

This function automatically calculates all three SEDI steps using defaults for most parameters. The defaults are stored in a file called assist.ini which is displayed after processing has completed. The values in assist.ini can be modified and the process repeated with these new values.

Process SEDI Step 1. Ratio File

Purpose

Calculate pixel / parameter ratios.

Parameters

Input SURFER data file
Output SURFER data file
Background image
Positive or negative relationship (P / N)
Number of pixels extracted per station (1, 3, 5, 9, 13)
Delimiter of input SURFER data file
Missing value in input file
Keep missing data in output file (y/n)

Process SEDI Step 2. Grid

Purpose

Interpolate a Surfer grid file of ratios from the ratio file.

Parameters

Input SURFER data file (from step 1)
Output SURFER grid file
Background image
Distance between gridlines (kilometers)
Search radius for interpolation (kilometers)
Number of nearest stations to use
Missing value in input file

Process SEDI Step 3. Image

Purpose

Create an image of estimated values from gridded ratios and pixel values.

Parameters

Input SURFER grid file (from step 2)
Output image file
Background image
Positive or negative relationship (P / N)
Image type
Slope
Intercept

Process Import Ida Luts

Purpose

Parameters

Remarks

See Color tables for a description of what a color table consists of.

Process Import Ascii Image

Purpose

Parameters

Remarks

Process Import Binary Image

Purpose

Parameters

Remarks

This function will append raw, 8-bit, binary data onto an IDA image header so the data can be displayed and processed in IDA. If the raw data is padded to some convenient record length, or if ancillary data is attached to the beginning or end of the record, the "number of pixels" parameter should equal the entire length of the record, not just the length of the actual data in the record.

Process Import Erdas Image

Purpose

Parameters

Remarks

Only 4- and 8-bit images are currently supported.

A Platte-Carre (geographic) projection is assumed for all images being imported. If a different projection is used, Process Header Edit should be used to modify the image header accordingly.

See File Open Erdas for more information on displaying ERDAS images directly in WinDisp3.5.

When importing single-band LAN images, a single band of a multi-band LAN image, or a GIS image, the values are imported as is, with no stretching.

When importing multi-band LAN images, one band is assigned to each of the red, green and blue colors. The image values for each band are stretched from the mean +/- 2 standard deviations to the range of 0 to 5 for the color assigned to that band. The result values are added together to create a final result between 0 and 215 according to the formula red + green*6 + blue*36. This technique was adopted from an algorithm used by Idrisi for the same purpose.

To display these multi-band LAN images correctly, you must use a special color table (called ERDASLAN.CLR) This color table has 6 intensities for red, green and blue for a total of 6*6*6=216 colors. The intensities are 0, 51, 102, 153, 204 and 255.
The start of the color table looks like this

From To Red Grn Blu Legend
0 0 0 0 0  
1 1 51 0 0  
2 2 102 0 0  
3 3 153 0 0  
4 4 204 0 0  
5 5 255 0 0  
6 6 0 51 0  
7 7 51 51 0  
8 8 102 51 0  
9 9 153 51 0  
10 10 204 51 0  
11 11 255 51 0  
12 12 0 102 0  
...          
215 215 255 255 255  

Process Import Erdas Trailer

Purpose

Parameters

ERDAS GIS trailer file to import
Color table to create

Remarks

Process Import Idrisi Image

Purpose

Parameters

Remarks

A Platte-Carre (geographic) projection is assumed for all images being imported. If a different projection is used, the image header should be modified accordingly with Process Header Edit.

Process Import Idrisi Vector

Purpose

Parameters

Remarks

Process Import Surfer Grid

Purpose

Parameters

Remarks

Process Import Surfer Plot

Purpose

Parameters

Remarks


To convert the plot file from plotter inches back into lat/long coordinates, this function needs to use the header parameters from the IDA image that had been converted to the SURFER grid file that was used to plot the contours. If the contours were not created from a converted image, a dummy image with a PLATTE-CARRE projection should be used.

This is, in fact, a very hokey function that should be used very carefully. ERDAS, IDRISI and ARC/INFO all provide much better raster-vector conversions.

Process Export Ascii Image

Purpose

Parameters

Remarks

Process Export Binary Image

Purpose

Parameters

Remarks


This function merely creates an 8-bit binary data file without the IDA header.

Process Export Erdas Image

Purpose

Parameters

Remarks


The IDA images are converted to 8-bit ERDAS images. The extension should be either .LAN or .GIS. Internally, the file format for GIS and single-band LAN files are identical.

A Platte-Carre (geographic) projection is assumed for all images being exported. If a different projection is used, the ERDAS image header should be modified accordingly.

Process Export Idrisi Image

Purpose

Parameters

Remarks

A Platte-Carre (geographic) projection is assumed for all images being exported. If a different projection is used, the Idrisi image header should be modified accordingly.

Process Export Idrisi Vector

Purpose

Parameters

Remarks

Process Export Surfer Grid

Purpose

Parameters

Remarks

If the IDA projection type is Platte-Carre (geographic), then the projection information will be transferred to the grid file. Otherwise, the projection information is ignored.

Process Export Surfer Blank

Purpose

Parameters

Remarks


Process Reproject

Purpose

Parameters

Remarks


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This manual was prepared by the Global Information and Early Warning System of the United Nations Food and Agriculture Organization
© FAO/GIEWS - 1999
E-mail: Giews1@fao.org