open source gis

OPEN SOURCE GIS A GRASS GIS Approach

by

Markus Neteler Istituto Trentino di Cultura (ITC-irst) Italy

Helena Mitasova North Carolina State University U.S.A.

KLUWER ACADEMIC PUBLISHERS Boston / Dordrecht / London

Contents

List of Figures List of Tables Foreword Preface Acknowledgments

xiii xix xxi xxv xxvii

1. OPEN SOURCE SOFTWARE AND GIS 1.1 Open Source concept 1.2 GRASS as an Open Source GIS 1.3 How to read this book -

1 1 3 4

2. PREREQUISITES TO USE GRASS 2.1 Hardware and software requirements 2.2 UNIX basics 2.2.1 What is UNIX? 2.2.2 Login and X Window 2.2.3 Managing 2.2.4 Running applications 2.3 Downloading and installing GRASS

7 7 8 8 9 11 15 19

files

3. GIS CONCEPTS AND GRASS 3.1 General GIS principles 3.1.1 Geospatial data models 3.1.2 Organization of GIS data 3.1.3 GIS functionality 3.2 Introduction to GRASS 3.2.1 Organization of the GRASS database 3.2.2 • Command structure " 3.2.3 A short GRASS sample session 3.2.4 GRASS file management

21 21 21 25 26 27 27 29 31 34

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4. PLANNING A GRASS DATABASE 4.1 Map projections and coordinate systems 4.1.1 Map proj ection principles 4.1.2 Geographic coordinate system: latitude-longitude 4.1.3 Universal Transverse Mercator Grid System 4.1.4 Lambert Conformal Conic Projection based systems 4.1.5 Gauss-Kruger Grid System 4.1.6 North American and European Datums 4.2 Working with different projections in GRASS 4.2.1 Creating a new LOCATION 4.2.2 Coordinate system transformations 5. WORKING WITH RASTER DATA 5.1 GRASS raster data model 5.2 Import and export of raster data 5.2.1 Importing raster data 5.2.2 Importing and geocoding of scanned maps 5.2.3 Exporting raster data 5.3 Viewing and managing raster map layers 5.3.1 Displaying raster data and assigning a color table 5.3.2 Raster map queries and profiles 5.3.3 Zooming and generating subsets from raster maps 5.3.4 Managing metadata of raster maps " 5.3.5 Reclassification of raster maps 5.3.6 Assigning category labels 5.3.7 Masking and handling of no-data values 5.4 Raster map algebra 5.5 Raster data transformation and interpolation 5.5.1 Automated vectorization of discrete raster data 5.5.2 Generating isolines representing continuous fields 5.5.3 Raster data transformation to sites model 5.5.4 Interpolation of raster data and resampling 5.5.5 Recoding of raster map types and value replacements 5.6 Spatial analysis with raster data 5.6.1 Map statistics and neighborhood analysis 5.6.2 Overlaying and merging raster maps 5.6.3 Buffering of raster features 5.6.4 Cost surfaces 5.6.5 DEM and watershed analysis 5.6.6 Landscape structure analysis and modeling

59 59 63 63 67 73 73 74 75 76 78 79 82 85 87 94 94 95 96 97 99 100 100 104 107 108 112 118

Contents

ix

6. WORKING WITH VECTOR DATA •• 6.1 GRASS vector data model, 6.2 Importing and exporting vector data 6.2.1 Importing vector data 6.2.2 Exporting vector data 6.3 Digitizing vector data 6.3.1 General principles for digitizing topological data 6.3.2 Digitizing in GRASS 6.4 Metadata and attributes management 6.4.1 Managing metadata of vector maps 6.4.2 Map attributes modifications 6.5 Viewing and analysis 6.5.1 Displaying vector map layers 6.5.2 Intersecting and clipping vector maps 6.5.3 Map reclassification 6.5.4 Feature extraction from vector data 6.6 Vector data transformation to/from raster and sites 6.6.1 Automatic vectorization of raster data 6.6.2 Discrete transformation of vector data to raster or sites 6.6.3 Interpolating raster surfaces from contour lines

121 121 123 123 131 133 134 135 141 142 142 143 143 144 146 147 148 148 150 151

7. WORKING WITH SITE DATA 7.1 GRASS site data model ' 7.2 Importing, creating and exporting sites 7.2.1 Importing site data 7.2.2 Digitizing site data 7.2.3 Generating site data within GRASS 7.2.4 Exporting site data 7.3 Viewing and managing site data 7.3.1 Displaying site data and creating subsets 7.3.2 Computing basic statistics . 7.4 Transformation from sites to rasters and spatial interpolation 7.4.1 Selecting an interpolation method 7.4.2 Interpolating with RST: tuning the parameters 7.4.3 Estimating accuracy 7.4.4 Interpolating large data sets (ft) 7.4.51 Surfaces with faults (ft) 7.4.6 Adding third variable: precipitation with elevation (ft) 7.4.7 Volume and volume-temporal interpolation (ft) 7.4.8 Geostatistics and splines

155 155 156 156 158 159 160 160 161 161 163 163 167 171 172 175 178 178 180

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OPEN SOURCE GIS

8. GRAPHICAL OUTPUT AND VISUALIZATION 8.1 Two-dimensional display and animation 8.1.1 Displaying map layers using the GRASS monitor 8.1.2 Creating a 2D shaded elevation map 8.1.3 Monitor output to PNG and HTML files (ft) 8.1.4 Animations in 2D space 8.2 Visualization in 3D space with NVIZ 8.2.1 Viewing multiple map layers 8.2.2 Querying and analyzing data in nviz 8.2.3 Creating animations in 3D space (ft) 8.2.4 Visualizing volumes (ft) 8.3 Creating hardcopy maps 8.3.1 Map generation with p s . map 8.3.2 Map design with Xfig and Sketch

183 183 183 186 187 189 190 190 195 196 201 203 203 204

9. SATELLITE IMAGE PROCESSING 9.1 Remote sensing basics 9.1.1 Spectrum and remote sensing 9.1.2 Satellite sensors 9.2 Satellite data import and export 9.2.1 Import of raw and geocoded satellite data 9.2.2 Export of multi-channel data sets 9.3 Understanding a satellite data set 9.3.1 Managing channels and colors 9.3.2 The feature space and image groups ., 9.4 Geometric and radiometric preprocessing 9.4.1 Geometric preprocessing 9.4.2 Radiometric preprocessing 9.4.3 Application: Deriving a surface temperature map from thermal channel 9.5 Radiometric transformations and image enhancements 9.5.1 /Image ratios 9.5.2 ' Principal Component Transformation (ft) 9.5.3 Fourier Transformation (ft) 9.6 Geometric feature analysis 9.6.1 Matrix filter: Spatial convolution filtering 9.6.2 Edge detection 9.7 Image fusion 9.7.1 Introduction to RGB and IHS color model 9.7.2 RGB color composites

207 207 207 209 212 212 215 215 215 219 221 221 228 234 236 236 237 239 243 243 245 246 247 248

Contents

9.8

9.7.3 Image fusion with IHS transformation 9.7.4 Image fusion with Brovey transformation Thematic reclassification of satellite data 9.8.1 Unsupervised radiometric reclassification 9.8.2 Supervised radiometric reclassification 9.8.3 Supervised SMAP reclassification

xi 249 251 252 254 258 261

10. PROCESSING OF AERIAL PHOTOS 10.1 Introduction to aerial photogrammetry 10.2 Orthophoto generation 10.2.1 From aerial photo to orthophoto 10.2.2 Aerial photo and LOCATIONS preparation 10.2.3 Orthophoto generation 10.3 Segmentation and pattern recognition for aerial images

263 263 266 266 268 270 278

11. NOTES ON GRASS PROGRAMMING 11.1 GRASS programming environment 11.1.1 Methods of GRASS programming 11.1.2 Level of integration 11.2 Script programming 11.3 Automated usage of GRASS 11.4 Notes on programming GRASS modules in C

281 281 282 283 283 290 292

12. USING GRASS: APPLICATION EXAMPLES 12.1 Erosion risk in Spearfish area 12.1.1 Computation of the LS factor 12.1.2 Estimating R, K, and C factors 12.1.3 Computing and analyzing erosion risk 12.2 GIS modeling for land management (ft) 12.2.1 Building the GIS database 12.2.2 Deriving new map layers 12.2.3 Land use analysis, problems and solutions

299 299 300 305 306 309 310 316 324

13. USING GRASS WITH OTHER OPEN SOURCE TOOLS (ft) 13.1 Geostatistics with GRASS and gstat 13.2 Spatial data analysis with GRASS and R 13.2.1 Spearfish data set analysis 13.2.2 Maas river bank soils data analysis 13.2.3 Using R in batch mode 13.3 GPS data handling ' 13.4 Maps in WWW: MapServer

335 336 341 343 351 361 363 364

References

369

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OPEN SOURCE GIS

Appendices A Summary of important GRASS commands A. 1 Display commands A.2 General commands A.3 Image processing commands A.4 Miscellaneous and map projection commands A. 5 Postscript and PPM driver commands A.6 Raster data commands A.7 Site data commands A.8 Vector data commands B Supported GIS formats and projections B. 1 Supported GIS data formats in GRASS B.2 List of supported ellipsoids, datums and projections C Customizing GRASS by environment variables D Usage UNIX text tools for GIS data preparation E Selected equations used in GRASS modules E.I Basic Statistics E.2 Interpolation E.3 Topographic analysis E.4 Insolation F MapServer sample configuration F.I MapServer definition file F.2 MapServer HTML template

377 377 377 379 380 381 382 383 387 388 391 391 392 395 399 403 403 404 405 410 415 415 418

Index 421