Algebraic Operations

Feature Description

Algebraic operations refer to spatial analysis of geographical features and phenomena using algebraic principles, performing mathematical operations and functions on one or multiple raster datasets. Operations on multiple raster datasets involve pixel value calculations at corresponding positions.

SuperMap provides comprehensive operation expressions, supporting not only common arithmetic operations (addition, subtraction, multiplication, division, rounding, etc.) but also custom expressions for raster arithmetic, conditional operations, logical operations, functions (including common functions, trigonometric functions), and composite operations.

Feature Entry

Data Tab->Data Processing->Raster->Algebraic Operations.
Toolbox->Data Processing->Raster->Algebraic Operations.

Parameter Description

Algebraic Operation Expression: Input algebraic operation expressions manually, or use the Raster Algebraic Operation Expression dialog for semi-automatic input through function wizard. Alternatively, quickly import/export operation expressions via corresponding functions.
Expression file format specifications:
```
<?xml version="1.0" encoding="UTF-8"?>
<SmXml:MathOperation xmlns:SmXml="http://www.supermap.com/xml">
    <SmXml:Expression>Con( [DEM.dem] > 1000,1,-9999)</SmXml:Expression>;
    <SmXml:PixelFormat>6400</SmXml:PixelFormat>
    <SmXml:BZip>TRUE</SmXml:BZip>
    <SmXml:BNoValue>TRUE</SmXml:BNoValue>
    <SmXml:BShowProgress>TRUE</SmXml:BShowProgress>
</SmXml:MathOperation>
```
The <Expression> field stores the algebraic operation expression from the expression dialog.

The <PixelFormat> field specifies pixel storage type for result dataset: 1=1-bit, 4=4-bit, 8=8-bit, 16=16-bit, 320=integer, 64=long integer, 3200=single-precision, 6400=double-precision.

<BZip> indicates dataset compression: FALSE=uncompressed, TRUE=compressed.

<BNoValue> controls NoValue cell handling: TRUE=ignore NoValue cells, FALSE=include in operations.

<BShowProgress> toggles progress bar display.
Pixel Format: Set pixel format for result dataset. 11 formats available including 1-bit, 4-bit, 8-bit, 16-bit, 32-bit, 64-bit, single and double. Details see Raster Dataset Pixel Formats.
Compress Result Dataset: Enable for compressed storage of output dataset.
Ignore NoValue Cells: When enabled, NoValue cells in input raster won't participate in operations, preserving original null values (typically -9999). Disabled state treats NoValue cells as regular values, potentially altering result dataset's min/max values.
View NoValue cell parameters through dataset properties:
- Right-click input raster dataset in Workspace Manager and select Properties.
- Check NoValue parameter in Raster section of properties panel (default: -9999).
Datasource: Select output datasource.
Dataset: Name the result dataset.

Environment Settings

The Environment section configures analysis environment parameters including geographic extent and clip bounds. For details, see Setting Analysis Environment.

Notes: