topic Re: Creating vector features from marker symbols on a jpg file? in Data Management Questions

Creating vector features from marker symbols on a jpg file?

FrancescaFernandez — Fri, 20 Apr 2012 07:47:06 GMT

Using this map which is (sadly) only available to me as a jpeg, I'd like to render each of the distinct features (ie. mined areas, lifted areas, cleared areas, incident points, and - if possible - confrontation lines) as separate shapefiles/layers in ArcMap 10. Short of manually plotting each individual dot and line - which does not strike me as particularly time-efficient nor accurate - is there any other way of achieving this?

Given that I'm a GIS novice, please feel free to overstate the obvious in your replies 😉 ...

Also, I've heard that scripting is an option but seeing as I have 48 hours to complete this, and only basic GIS experience under my belt, I'm not sure how feasible that would be. Any ideas?

Thanks in advance guys!

(NB. I've also posted this message on the 'Map Automation' and 'Education' boards as I wasn't sure where it would be most appropriate, so Mods please feel free to redirect.)

Re: Creating vector features from marker symbols on a jpg file?

SteveKloiber — Fri, 20 Apr 2012 13:20:36 GMT

Here's one possible concept for a process.

You can select specific colors from an image and create a new raster dataset with the selected colors. You can even do this sort of color filtering/selection with software like Adobe Photoshop. You can then use a raster to vector conversion tool. This would probably work better if the image were originally stored as an 8-bit, unsigned integer raster. JPEG often uses dithering and thus the edges of your symbols are likely to be some gradation of color from the pure symbol to the background color.

Adding few more details to this concept.

1) Convert the image to a single band format, with 16-bit data or less (probably better if you can use 8-bit). I don't know the specific tool to use in ArcGIS, but this type of image processing is readily available in lots of basic image software like Adobe Photoshop.

2) Bring the image into ArcMap and use the georeferencing tool to georeference the image (if it isn't already georeferenced).

3) Add a color map (Data Management>Raster>Raster Properties>Add Colormap)

4) Use the reclassify tool (Spatial Analyst>Reclass>Reclassify) to reclassify the specific color that corresponds to one of your desired features to a value of 1 and all other colors reclassified to a value of zero.

5) Use the tool Raster to Point (Conversion Tools>From Raster>Raster to Point).

Buenas Suerte

Re: Creating vector features from marker symbols on a jpg file?

FrancescaFernandez — Fri, 20 Apr 2012 14:55:50 GMT

Thanks kloi0001! That all sounds totally feasible - even at my level of expertise. 🙂 I'll give it a shot and let you know how I get on