5

Data on the changes in voting district delimitations in SA is available as a series of maps (no shapefiles made official). I'd like to create a shapefile by scraping the boundaries from the individual pdf's and putting them together. Is it viable? What would be the easiest/fastest/best way? Ideally the process would be automated.

Example of the document: Schedule 1 MSA Detailed ward maps (last downloadable link) http://www.demarcation.org.za/index.php/ward-delimitation/2014-2015/western-cape/city-of-cape-town

4

ESRI provides the extension of ArcScan and you can complete Automatic Vectorization to create content. This of course does require you to do a bit of manual work. but less than re-digitzing.

To turn ArcScan on:

  • click Customize>Extensions

enter image description here

  • Turn on ArcScan

enter image description here

  • Right Click the grey space on your toolbar (where no other tools are). select ArcScan

enter image description here

There are lots of tutorials on how to use ArcScan

  • What license level is needed for this extension? – Jyler Feb 26 '16 at 19:06
  • 1
    @Jyler it is included with all license levels at ArcGIS 10.1 – MDHald Feb 26 '16 at 19:23
  • thanks @MDHald- Is ArcGis only for Windows...? – Anna Magdalena Feb 26 '16 at 19:37
  • @Jyler - it is available for Mac but you would have to virtualize your machine (which is a fancy way of saying it's not allowed on Mac, Linux, etc) - Here is some rough documentation on how to do it. – MDHald Feb 26 '16 at 19:40
1

One way to go about this would be to convert your PDFs to PNG or another image format that your GIS software can work with and georeference them. Then you could digitize the boundaries and save them as a shapefile. Obviously this is not automated or fast, though it is easy. Is there a reason you're unable to obtain the source files?

  • thanks! They are not released yet by the official board and might not be for some time. However, the elections for which they were defined are getting closer- I work with journalists to see whether the changes were neutral or political. 'convert your PDFs'? to jpg? How do I georeference it? First time doing this type of analysis – Anna Magdalena Feb 26 '16 at 17:20
  • I keep seeing references to ArcGis. Is this the only option? – Anna Magdalena Feb 26 '16 at 17:23
  • QGIS is a free program that has very similar capacities for ArcMap. What GIS program do you use? I'm assuming if you are trying to create shapefiles, you are probably using some kind of GIS program already... – Sara Barnes Feb 26 '16 at 17:31
  • Here is one link that describes how to georeference in QGIS: qgistutorials.com/en/docs/georeferencing_basics.html – Sara Barnes Feb 26 '16 at 17:32
  • @SaraBarnes: I'm using Python (all stack e.g. geopandas, fiona etc) and command line tools – Anna Magdalena Feb 26 '16 at 17:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.