topic Re: Turning images into a Shapefile? in Mapping Questions

Turning images into a Shapefile?

AlbanXhema — Tue, 03 Mar 2015 17:13:34 GMT

So I have a soil map that is currently just an image in my GIS and I want to turn it into a shapefile so that I can manipulate the colors and control each soil category differently. Currently I have just been drawing them in freehand, but this creates a difference between the contours in the soil map and my GIS. It also takes a lot of time. Is there anyway I could at least make sure that the shapefiles I'm making line up exactly with the lines of the contours in the soil map? Again, the soil map is just an image and I need to create a digitized version of it.

Re: Turning images into a Shapefile?

LisaTurner — Tue, 03 Mar 2015 17:57:57 GMT

Hey Alban,

Not sure if this will help or not, but thought I would share the link. What is ArcScan?—Help | ArcGIS for Desktop

Re: Turning images into a Shapefile?

AlbanXhema — Thu, 05 Mar 2015 18:04:23 GMT

When I go to use editor to select the .jpeg I want to edit, nothing is showing up. Is there anyway to convert a .jpeg to a raster?

Re: Turning images into a Shapefile?

LisaTurner — Thu, 05 Mar 2015 21:16:55 GMT

Hey Alban,

I believe a jpeg is a raster already. Have you tried opening base maps, or other maps with your jepg to see if the jpeg is located spatially where you think it is?

Re: Turning images into a Shapefile?

DarrenWiens2 — Thu, 05 Mar 2015 21:23:47 GMT

As Lisa touches on, your first step is to georeference your raster, if not done already. Then, your task is to turn that raster into something more usable, using ArcScan or manually tracing the lines into a polygon/polyline feature class. I've also used a supervised classification to train the data into usable classes (i.e. draw training polygons for a few known classes, then run the classification to apply those training polygons to the entire raster).

Re: Turning images into a Shapefile?

AlbanXhema — Thu, 05 Mar 2015 21:25:59 GMT

Hello Lisa,

Thank you for your help so far, I'm very appreciative. The jpeg is georeferenced in the GIS and lines up with everything, just when I open the editor it doesn't come up as an option that I can select. Do you think it might just be something with the editor misreading it? The jpeg is showing up in the table of contents and is part of the GIS, it's just not showing up when I start editing.

Re: Turning images into a Shapefile?

AlbanXhema — Thu, 05 Mar 2015 21:27:16 GMT

Right now I've just decided to freehand draw everything, I was just hoping there was a way to do it faster and to make it more exact

Re: Turning images into a Shapefile?

DarrenWiens2 — Thu, 05 Mar 2015 21:31:36 GMT

You can't "edit" rasters, but you can turn that raster into an editable vector polygon or polyline feature class using ArcScan or raster classification/raster to polygon operation.

Re: Turning images into a Shapefile?

AlbanXhema — Thu, 05 Mar 2015 21:38:22 GMT

Right, my problem when I go to turn the raster into a vector through ArcScan is that it doesn't come up as a selectable option

Re: Turning images into a Shapefile?

LisaTurner — Thu, 05 Mar 2015 21:49:31 GMT

Hey Alban,

I've never used ArcScan, but I was reading more and found this ArcGIS Desktop It's also possible it is easier to draw it in freehand. Good luck in either method you choose.

Re: Turning images into a Shapefile?

DarrenWiens2 — Thu, 05 Mar 2015 21:49:43 GMT

Have you symbolized your raster as a bi-level image?

ArcScan can vectorize any raster format supported by ArcGIS so long as it is represented as a bi-level image. This requires that you symbolize raster layers with two unique colors. You can use either the ArcMap Unique Values or Classified rendering options to separate the raster into two colors.

Re: Turning images into a Shapefile?

AlbanXhema — Thu, 05 Mar 2015 22:17:12 GMT

No, it's still in RGB. Thank you, I was wondering how to turn it into a bi-level image, I forgot that was necessary.

Re: Turning images into a Shapefile?

ChadCollins3 — Fri, 06 Mar 2015 12:08:22 GMT

I would ensure that the JPEG file extension is .jpg and not .jpeg, do this using Windows Explorer.