00:06In ArcGIS 10.1, we've added an option to automatically georeference your images.
00:12You can access this option from the georeferencing toolbar.
00:16I'm just going to open it from the Customize menu > Toolbars > Georeferencing.
00:25Now I'm going to add my image that is referenced to the display.
00:30So here I have a QuickBird scene.
00:32I can take a look at its Properties.
00:35It's Standard2A processing, and it was taken in 2005.
00:39I'm going to add its Multispectral product to the window.
00:43Then I'm going to zoom to an area...
00:46...where I know that my ungeoreferenced image basically lines up.
00:56Next, I'm going to add in my unreferenced image.
01:01And you can see that the georeferencing is unknown.
01:07So there's a few things I can do.
01:09First, I'm going to make sure that it's selected in the Georeferencing toolbar.
01:15Then, I'm going to fit the image to the display.
01:20And this brings it in.
01:25There are other things you can do.
01:26In this case, my image is oriented approximately the same as the other image.
01:31But I can do things like scale, shift and rotate the image into place.
01:36I can also choose to rotate it, a prescribed amount, or to flip it, a certain way.
01:45In this case, I'm just going to click the auto-georeferencing button and let it work.
01:49This process finds matching control points between the two images...
01:53...based on their spectral characteristics.
01:55Therefore, to get the best results, it's recommended that the two images...
02:00...have similar spectral characteristics in that they be as similar as possible.
02:04For example, two natural color images like we have here of similar pixel sizes.
02:10You won't get good results if you use a low-resolution image as the base...
02:14...to auto-register a high-resolution image.
02:17You also won't get good results if you try and auto-register a black-and-white image...
02:20...to a color image.
02:22It's also best to center the display in the approximate location...
02:26...of the ungeoreferenced image as I have done here.
02:30So once the process is complete, you can examine the control points visually, or...
02:34...by looking at them in the display or you can open the links table.
02:40So here you can see information like the RMS Error.
02:50You can also go in and look at the link.
02:55You can remove it or add in new ones if you want to as well.
03:03So the next thing I'll do is I can simply choose to update the georeferencing...
03:09...which will update the transformation stored on disc...
03:12...or I can choose to rectify it, which will write out a new georeferenced image.
03:16In my case, I just want to update...
03:18...the information that is stored on disk and not create any extra image files.
03:24And now I can continue to work with my image and it into...
03:27...other ArcMap sessions as a georeferenced image.
03:31Next, I'm going to move onto another example.
03:34Here I have another image that's basically in the right location, but it's not quite right.
03:41This is quite typical of some satellite imagery...
03:44...that isn't processed as accurately as other imagery.
03:50So here you can see that my roads...
03:53...in my vector file don't quite line up with my roads in my image.
03:58And if I want to make sure that it's my image that's off, and not my vectors that are off.
04:04What I'm going to do is I'm going to bring in a basemap...
04:07...that I can get to from ArcMap that comes from ArcGIS online.
04:10I'm going to open the Imagery Basemap because I'm going to ultimately use it...
04:15...to fix the georeferencing of this image that's being displayed.
04:21So, because it's a basemap, it automatically gets pushed to the bottom...
04:24...of the table of contents and underneath everything.
04:26So I've turned off my Multispectral scene.
04:30And you can see that my roads line up perfectly with this Basemap image.
04:39So next, I'm just going to zoom back out and turn on my Multispectral scene...
04:44...and I'm going to use my Basemap to correct the image that I displayed.
04:48You can see that nothing is selected in the Georeferencing toolbar.
04:52And this is because the projection isn't appropriate for georeferencing.
04:58So I'm just going to change the Properties of my Data Frame.
05:03I'm going to choose one of the Layers that are already in the map and click OK.
05:08And, yes, I want to reproject everything.
05:13So next, I'm just going to make sure that image I want is selected, which it is.
05:18I don't need to reorient this one; I just need to click auto-georeferencing.
05:24So, just as before, the statistics of the imagery basemap...
05:29...and the statistics of my image are going to be calculated...
05:34...then the two images will be compared to find the matching control points.
05:42So now I can zoom back in...
05:47...and I can see that my vectors do line up much better than they did before.
05:56And just as before I can choose to either update...
06:02...or rectify the image by writing in a new file.
Automatic Georeferencing in ArcGIS 10.1
This video demonstrates how to georeference imagery in ArcGIS using a tool to automatically collect the control points.
- Recorded: Jun 8th, 2012
- Runtime: 06:15
- Views: 5286
- Published: Jun 20th, 2012
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