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I am developing a GIS application like this:

image

By now my steps are:

  1. I have got a jpg file, 5040 x 8179 dimension. In this map, the roads, rivers, towns etc. are marked.
  2. I am using .Net to develop and this requires a shp file to be used properly.
  3. I tried using qGIS to vectorize this jpg and georeferencing it but the shapefile that comes out is like full green color etc..

How to convert my original jpg map data to shp format?

I have very little experience in GIS.

PolyGeo
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vhmangaiha
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  • raster to vector can be problematic - if you can extract from pixel colours it might have issues - try to convert to black and white the contrast can be more effective, – Mapperz Feb 18 '13 at 18:52
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    As Mapperz said, this is a problematic thing. Does your client/employer/whomever have the data that generated the map you are trying to convert in a vector format that they can provide? – Kevin Feb 18 '13 at 19:11
  • they have only the photoshop file i.e. psd file only ...From this we generate the jpg file.. – vhmangaiha Feb 18 '13 at 19:27
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    @Mapperz colors are needed , rivers are blue, roads are brown.. etc.. – vhmangaiha Feb 18 '13 at 19:40
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    You should look at similar questions tagged with vectorising. You will find this question discussed before and there are many potential ideas you could try. – RyanKDalton Feb 18 '13 at 20:49
  • Is this a one-off, or do you need to digitize many maps? There are really no short cuts here; these things tend to require lots of hand holding and judgment, especially if topology matters. – ako Feb 18 '13 at 23:50
  • Yes this is one-off, i can reuse this map .. – vhmangaiha Feb 19 '13 at 03:18
  • Are you sure the features you require are not available for download somewhere online? Often roads, rivers, cities, etc are freely available for download. You could save yourself a lot of time this way. – Fezter Feb 19 '13 at 03:44
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    There are free shapefiles and a gazetteer for the whole of India at http://www.diva-gis.org/gdata and you could extract the data for Mizoram from these. They might be of use. – nhopton Feb 19 '13 at 08:40
  • I have that map , i am coding currently in that.. The map that they have made is not available on the net.. How do i actually get the map of Mizoram from that big map. – vhmangaiha Feb 19 '13 at 13:17
  • This can only be vague because I don't have the dataset. But you should be able to display the data for Mizoram by loading say the Admin Level 3 layer (I don't know what this will be called in your case), right-clicking on it in the layers panel and selecting 'Query' (or in Master, 'Filter'). From here you can build an SQL query that will load just the Mizoram data. Have a look at the shapefile's attribute table before you start, which should give you some idea which column to use for your query. Sorry I can't be more specific. N. – nhopton Feb 19 '13 at 19:26
  • If you get stuck with the query it would probably be best to start a new question, "How do I query a shapefile?" perhaps. But check first to see if this topic is already covered somewhere else here. N. – nhopton Feb 19 '13 at 19:36

1 Answers1

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If all you have is the jpg, then I would suggest georeferencing the jpg and then manually digitizing the roads/rivers/etc vectors. That will give you the best control over the result, I personally have never had good luck with using raster-vector conversions in a situation like this.

Unfortunately, sometimes the best option is to just do it the hard way.

Kevin
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