Free Geography Tools

SAGA GIS (System For Automated Geoscientific Analyses) is a raster/terrain-oriented GIS program (some vector functions), with a modular structure that makes it easy to add additional capabilities. After being in release candidate mode for about a year, the final official version 2.0.0 was released about two weeks ago, replacing the previous version 1.2 stable release. Probably the biggest change is the move from Windows-only to a multi-platform release supporting both Windows and Linux. A quick examination of the module packages shows that a few new modules have been added, but most are unchanged. However, module management has been significantly improved with the addition of a “Modules” tab to the Workspace window, and in general it’s easier to pull up data in the new version.

Best of all, there’s been a huge improvement in documentation. Version 1.2 had a good introductory 200-page manual that’s still worth downloading and reading, but many of the modules had virtually no documentation at all. Version 2.0 now has a terrific 400-page manual, available at the SourceForge download page along with a copy of the demo data used in the manual. And while even the manual doesn’t cover all the functions of the different modules, clicking on a module in the “Modules” window and then clicking on the module’s “Description” tab brings up a cursory description of the module and the input parameters. While it will still take some time to figure the module’s operation out, that’s still better than the way it was with version 1.2. A listing of the available modules is at the bottom of this post, after the fold.

It’s a good thing there are now two good manuals, because program function takes some getting used to. SAGA uses its own raster grid format (.sgrd for version 2.0), so grids in other formats have to be imported into the program (and exported into other formats as well). Setting parameters for individual data layers also takes some getting used to. But given the huge number of module functions available in this program, it’s worth spending some time figuring out how to use it. I hope to cover some of the modules not documented in the manuals in future posts (I’ve already covered using SAGA to convert raster graphics to shapefile format in this post).

A list of modules in SAGA 2.0 follows below the fold (taken from the user manual).

Contributions – T. Wutzler

• CompleteLinkage
• RGBOverlay

Geostatistics – Grids

• Multiple Regression Analysis (Grids/Points)
• Radius of Variance (Grid)
• Regression Analysis (Grid/Points)
• Representativeness (Grid)
• Residual Analysis (Grid)
• Statistics for Grids
• Zonal Grid Statistics

Geostatistics – Kriging

• Ordinary Kriging
• Ordinary Kriging (Global)
• Universal Kriging
• Universal Kriging (Global)

Geostatistics – Points

• Semivariogram

Grid – Analysis

• Accumulated Cost (Anisotropic)
• Accumulated Cost (Isotropic)
• Aggregation index
• Analytical Hierarchy Process
• Change Vector Analysis
• Covered Distance
• Cross-Classification and Tabulation
• Fuzzify
• Fuzzy intersection grid
• Fuzzy union grid
  Layer of extreme value
• Least Cost Path [Interactive]
• Ordered Weighted Averaging (OWA)
• Pattern analysis
  Polar To Rect
• Rect To Polar
• Vegetation Index[distance based]
• Vegetation Index[slope based]

Grid – Calculus

• Function
• Geometric Figures
• Grid Calculator
• Grid Normalisation
• Grid Volume
• Random Field
• Random Terrain Generation

Grid – Discretisation

• Cluster Analysis for Grids
• Grid Segmentation
• Grid Segmentation (b)
• Grid Skeletonization
• Supervised Classification

Grid – Filter

• Filter Clumps
• Gaussian Filter
• Laplacian Filter
• Multi Direction Lee Filter
• Simple Filter
• User Defined Filter (3×3)

Grid – Gridding

• Inverse Distance
• Modified Quadratic Shepard
• Nearest Neighbour
• Shapes to Grid
• Triangulation

Grid – Spline Interpolation

• B-Spline Approximation
• Multilevel B-Spline Interpolation
• Thin Plate Spline (Global)
• Thin Plate Spline (Local)
• Thin Plate Spline (TIN)

Grid – Tools

• Aggregate
• Change Cell Values [Interactive]
• Change Grid Values
• Change Grid Values – Flood Fill [Interactive]
• Close Gaps
• Close One Cell gaps
• Combine Grids
• Convert Data Storage Type
• Create Constant Grid
• Crop to Data
• Cutting [Interactive]
• Grid Buffer
• Grid Orientation
• Grid Value Request [Interactive]
• Grids from classified grid and table
• Invert Data/No-Data
• Merging
• Patching
• Reclassify Grid Values
• Resampling
• Sort Grid
• Threshold Buffer

Grid – Visualisation

• Color Blending
• Color Palette Rotation
• Create 3D Image
• Fit Color Palette to Grid Values
• RGB Composite

Import GPS Data

• GPSBabel
• GPX to shapefile

Import/Export – ESRI E00

• Import ESRI E00 File

Import/Export – Grids

• Export ESRI Arc/Info Grid
• Export Grid to XYZ
• Export Surfer Grid
• Export True Color Bitmap
• Import Binary Raw Data
• Import ESRI Arc/Info Grid
• Import Erdas LAN/GIS
• Import Grid from Table
• Import MOLA Grid (MEGDR)
• Import SRTM30 DEM
• Import Surfer Grid
• Import USGS SRTM Grid

Import/Export – Grids using GDAL

• Import using GDAL (various raster formats)

Import/Export – Images

• Export Image (bmp, jpg, png)
• Import Image (bmp, jpg, png, tif, gif, prm, xpm)

Import/Export – Shapes

• Export Atlas Boundary File
• Export GStat Shapes
• Export Shapes to Generate
• Export Shapes to XYZ
• Export Surfer Blanking File
• Import Atlas Boundary File
• Import GStat Shapes
• Import Shapes from XYZ
• Import Surfer Blanking Files

Import/Export – Tables using ODBC

• Import Table via ODBC

Lectures – Introducing Module Programming

• 01: My first module
• 02: Pixel by pixel operations with two grids
• 03: Direct neighbours
• 04: Direct neighbours – more…
• 05: Direct neighbours – slope and aspect
• 06: Extended neighbourhoods
• 07: Extended neighbourhoods – catchment areas (trace flow)
• 08: Extended neighbourhoods – catchment areas (parallel)
• 09: Extended neighbourhoods – catchment areas (recursive)
• 10: Dynamic Simulation – Life
• 11: Dynamic Simulation – Soil Nitrogen Dynamics
• 12: First steps with shapes
• 13: Reprojecting a shapes layer
• 14: Vectorising channel lines

Projection – GeoTRANS

• GeoTRANS (Shapes)
• GeoTrans (Grid)

Projection – Georeferencing

• Create Reference Points [interactive]
• Georeferencing – Grids
• Georeferencing - Shapes

Projection – Proj4

• Proj4 (Grid)
• Proj4 (Shapes)

Recreations – Fractals

• Bifurcation
• Fractal Dimension of Grid Surface
• Gaussian Landscapes
• Mandelbrot Set [interactive]
• Newton-Raphson [interactive]
• Pythagoras’ Tree

Recreations – Games

• Mine Sweeper [interactive]
• Sudoku [interactive]

Shapes – Grid

• Add Grid Values to Points
• Clip Grid with Polygon
• Contour Lines from Grid
• Get Grid Data for Shapes
• Gradient from Grid
• Grid Statistics for Polygons
• Grid Values to Points
• Grid Values to Points (randomly)
• Vectorising Grid Classes

Shapes – Line

• Convert Polygons to Lines

Shapes – Lines (extended)

• Simplify Lines

Shapes – Points

• Add coordinates to points
• Convert a Table to Points
• Count Points in Polygons
• Create Point Grid
• Distance Matrix
• Fit N Points to shape
• Points from Lines

Shapes – Polygons

• Convert Lines to Polygons
• Geometrical Properties of Polygons
• Polygon Centroids
• Polygon Intersection
• Polygon statistics from points

Shapes – Tools

• Assign a Table to Shapes
• Create Chart Layer (bars/sectors)
• Create Empty Shapes Layer
• Create PDF Report for Shapes Layer
• Create Web Content [interactive]
• Create graticule
• Cut Shapes Layer
• Cut Shapes Layer [interactive]
• Merge Shapes Layers
• New layer from selected shapes
• Query builder for shapes
• Search in attributes table
• Select by theme
• Separate Shapes
• Split Shapes Layer
• Summary
• Transform Shapes

Simulation – Cellular Automata

• Conway’s Life
• Wa-Tor

Simulation – Fire Spreading Analysis

• Fire Risk Analysis
• Simulation

Simulation – Hydrology

• Overland Flow – Kinematic Wave D6
• Soil Moisture Content
• TOPMODEL
• Water Retention Capacity

Simulation – Modelling the Human Impact on Nature

• 01: A Simple Litter System
• 02: Carbon Cycle Simulation for Terrestrial Biomes
• 03: Spatially Distributed Simulation of Soil Nitrogen Dynamics

TIN – Tools

• Flow Accumulation (Parallel)
• Flow Accumulation (Trace)
• Gradient
• Grid to TIN
• Grid to TIN (Surface Specific Points)
• Shapes to TIN
• TIN to Shapes

Table – Calculus

• Function Fit
• Table calculator
• Table calculator for shapes
• Trend for Shapes Data
• Trend for Table Data

Table – Tools

• Create Empty Table
• Enumerate a Table Attribute
• Rotate Table

Terrain Analysis – Channels

• Channel Network
• D8 Flow Analysis
• Overland Flow Distance to Channel Network
• Strahler Order
• Vertical Distance to Channel Network
• Watershed Basins
• Watershed Basins (extended)

Terrain Analysis – Compound Analyses

• Standard Terrain Analyses

Terrain Analysis – Hydrology

• Cell Balance
• Downslope Area [interactive]
• Edge Contamination
• Flow Depth [interactive]
• Flow Path Length
• Flow Sinuosity [interactive]
• Flow Tracing
• Isochrones Constant Speed [interactive]
• Isochrones Variable Speed [interactive]
• Parallel Processing
• Recursive Upward Processing
• SAGA Wetness Index
• Slope Length
• Topographic Indices
• Upslope Area
• Upslope Area [interactive]

Terrain Analysis – Lighting, Visibility

• Analytical Hillshading
• Incoming Solar Radiation
• Insolation
• Visibility (single point) [interactive]

Terrain Analysis – Morphometry

• Convergence Index
• Convergence Index (Search Radius)
• Curvature Classification
• Downslope Distance Gradient
• Hypsometry
• Local Morphometry
• Morphometric Protection Index
• Multiresolution Index of Valley Bottom Flatness (MRVBF)
• Real Area Calculation
• Surface Specific Points

Terrain Analysis – Preprocessing

• Fill Sinks (Planchon/Darboux, 2001)
• Sink Drainage route Detection
• Sink Removal
• Terrain Analysis – Profiles
• Cross Sections
• Cross Sections
• Flow Path Profile [interactive]
• Profile [interactive]
• Profile from points
• Profiles from lines
• Swath Profile [interactive]