Developing Geospatial Solutions using Open Source
This is one of the three books identified by the Education and Curriculum Committee that should be written. The other books are Using Open Source GIS and Developing Web Mapping Solutions Using Open Source.
Approach for writing this book
Using the application and programming language categories from http://freegis.org we'll gather problems or use cases, maybe divide them into subproblems, and describe how they can be solved using the free tools.
The tools are programming languages, libraries, command line tools, and customizable applications.
This book is about "I know which problem I need to solve and it can't be solved, at least easily or without trouble, by simply using some free GIS tool".
We exclude web mapping problems from this one since it is the topic of book 3.
Provide here an analysis of the meta problem description above.
Copy the categories and
programming languages: C, C++, Java, Python, Tcl/Tk, Perl, (Visual) Basic, PHP, C#, Fortran, Delphi, Ruby, SWF, Other (Other has zero entries in freegis.org).
- Problem: Share GPS data between applications
- Subproblem: Parse GPX
- Explanation: GPX is an XML application for GPS data. Parsing gives us the GPS data.
- Problem:
- Subproblem: GeoTag Media
- Explanation:
- Problem:
- Subproblem: Track logs
- Explanation:
- Problem: Edit a GPS track
- example data
- Requirements: Show the track on a map as editable lines, show the coordinates on a spreadsheet allowing edits, link the two representations
- Subproblem: Import the GPS track to the editor
- Subproblem: Export the track from the system
- Problem: Merge GPS tracks
- Explanation: Allow you to view several GPS traces, delete certain points, and average others together.
- Use: You survey a route several times, and want a single trace of the best average over the traces
| Use case | Description | Perl | Ruby | Python | Shell |
| Parse GPX | What is GPX? | Perl based solution | Ruby based solution | PyGPX | shp2gpx.sh and gpx2shp.sh(scripts calling 'gpsbabel') |
| GeoTag Media | RDFWeb geoloc_media.pl (original geoloc_media) | Ruby? | Python? | Shell? | |
| Track logs | Geo::Track::Log | Ruby | Python | Shell? | |
| Track merge | Ruby? | Python? | gpsbabel can perform related GPS track operations |
Projection-Conversion
- Problem: Convert between WGS84 and local projections
- Problem: Convert from lat+long to easting and northing, as used on printed maps
Check out the Axis Order Confusion issue which arises whenever adressing geographic coordinates with IT systems.
| Use case | Description | Perl | Ruby | Python | Java | JavaScript | Shell |
| Change between projections | Perform a Helmert Transform | MySociety Code | geo_helper.py | Jcoord | JScoord | cs2cs tool | |
| Convert from lat+long to easting+northing | Geo::Coordinates::OSGB | geo_helper.py | Jcoord | JScoord | cs2cs tool | ||
| Work with old maps / data in Cassini Projection | Convert between Cassini and its base elipsoid | geo_helper.py | cassini-coord.js |
GPS and EXIF
- Problem: Extract GPS exif tags from photos
- Problem: Add GPS exif tags at the time a photo is taken
- Problem: Add GPS exit tags to photos, based on the time they were taken and a GPS track
| Use case | Description | Perl | Ruby | Python |
| Get GPS EXIF data | Extract lat and long from GPS Exif tags | pexif | ||
| Set GPS EXIF date | Add lat and long GPS Exif tags | pexif |