An overview of available GIS softwares
GRASS = Geographic Resource Analysis Support System http://grass.osgeo.org/ SAGA = a System for an Automated Geographical Analysis http://www.saga-gis.uni-goettingen.de/html/ QGIS = Quantum Graphical Information System http://www.qgis.org/ Software ArcGIS SAGA GRASS/ QGIS Cost At least $800.00 each version and the registration has to be annually renewed Free Free Data handling Never had a problem with any file size. However very fuzzy with the type of input file. Seems to be better than GRASS with the same file size Not good for any file of size close to 1 GB. Can deal with a variety of input file formats. Sophistication Standing at version 9.3; the 3D component is very effective Standing at version 2.1 so can’t expect much. No built-in command to calculate area Version 6.4.3. Has tools specific just for LIDAR image processing. Interface 3 in 1: display/ working directory/ command line 3 in 1 More convenient when coupled with QGIS Available help Yes. yes Open source so the users can actually interact with each other
Other geospatial tools
Other free tools that can expedite data preparation: www.batchgeocode.com: generate DMS geographical coordinates from address, can process 500 addresses each time and return a KML file to use with GoogleEarth. ExpertGPS™: not free but a trial of 30 days is available, which is more than enough for this step. Among its many functions, can return a shapefile to be used directly in a GIS software without dropping all the attributes. So far this is the fastest and most effective way to get a vector map from a spreadsheet in an open source GIS program.
Questions to ask before feeding data into any GIS program
- are all the associated files available? - what is the file size? - what is the input file format? is it compatible with the GIS program in use? - what is the projection? - raster or vector file? in case of a figure, what is the best resolution and how much digitization is required?
From the discussion above GRASS/ QGIS is the way to go so henceforward all the instructions will be given regarding this software.
Ways to create a shapefile
- from a spreadsheet without knowing the coordinates beforehand - from a dbf file: create a void shapefile then connect it to the desired dbf - from a csv file: key column when creating a new table. If there is already an ID column in your data table e.g. Object-ID, set it as the key column as per figure other than the software will automatically assign a new column named cat as key column. The new csv file will now have a dbf tail to it e.g. example.csv example_csv_dbf.dbf - from a figure (jpeg is the best format): hand digitization
How to load a shapefile into GRASS/ QGIS
- a few Windows versions miss out on a small file during installation and will crash with the following error: g.proj-exe - to keep track of the coding and any error during a process: Config Preferences User GUI settings Select as per diagram - properly define home directory, then a location and a mapset. A location to GRASS is like an .mxd file to ArcGIS while a mapset to GRASS is like a data frame to ArcGIS. - to avoid bickering in terms of projection since GRASS will not display data unless the projections of the location and the input match … - GRASS can upload one or multiple files at a time but pay close attention to backlash in the path to the target input file. Turn every forward lash into backlashes and make sure there is no space in the file name - If the program flags errors in filtering out small area, reset the min-area snap to be smaller.
QGIS
GRASS itself is not efficient in calculating distance and area but coupled with QGIS this can be done. A few notes to get along with QGIS: - define the path to the location of installed GRASS - select Show maptips - check the unit of measurement: Settings Project Properties Unit Meters