Using ArcGIS
Google Earth has great high resolution aerial imagery available free to the public. It's a great GIS viewer program and it's easy to use, however sometimes I need to do more with the imagery so I import it into ArcGIS by georeferencing it.
This tutorial will explain an easy and accurate way to georeference images from Google Earth in ArcMap. I will be using 2000 TIGER/Line data in Little Rock, AR for demonstration purposes.
I start off with a base map of the area of interest in ArcMap using the TIGER data. This is not a neccessary step, I just want to show how the image will line up properly to the data set when it is finalized.
Next open Google Earth and zoom in to the area of interest. I usually zoom out one magnitude more than my area of interest in ArcGIS so I will have enough aerial image to cover the area.
Now I will pick out 4 locations on the Google Earth map that are equally distributed and are good visual landmarks. This will allow us to easly find them in ArcMap when we get the image imported. Try to use features that are permanent (i.e. buildings, intersections, bridges) and are easy to spot in the image.
We need to get the coordinates for each of these points while in Google Earth. Right-click your point and choose "Edit" to pull up the properties of the point. Check the "Advanced" checkbox and click on the "Location" tab to view the latitude and longitude.
Open Notepad or any text editor and paste in the coordinates for each point in a tab-delimited format like the text below.
station xCoord yCoord
4 -92.263082 34.742178
2 -92.282934 34.741464
3 -92.283584 34.752602
1 -92.265551 34.754582
Save the file as pointLocations.txt, we will be using it later in ArcGIS.
Next turn all the points off by unchecking them in the Places list and click "File > Save Image". Save the image in an accessable place for ArcGIS.
In ArcGIS make sure you have the Georeferencing toolbar open. If not turn it on by clicking "View > Toolbars > Georeferencing". Next add the exported image to your view via the Add Data button. Browse to your exported aerial image and add it to your layers. You will see a prompt regarding missing geospatial information, just ignore it. You will not be able to see the image immediately on the map, it will only appear in the layers list.
Click on the Georeferencing toolbar and select "Fit to Display" The image will now appear in your view. If you can't see the image, it may be because it is under other layers in the map. I usually turn off any polygon data that may interfere with my georeferencing. In this case I will turn of Urban Areas and Water polygons.
Now we will add the text file we created earlier as a data layer. Click the Add Data button and browse to your pointLocations.txt file. It will appear in the Source tab of the layers window.
Right-Click the text file in the source list and select "Display XY Data". Match up the X and Y fields respectively and click OK.
This creates a new data layer called pointLocations.txt Events and inlcudes the 4 points on the map now. Right-Click the layer and select Zoom to Layer to view the entire points. I usually change the color of the symbol to something bright so I can see it clearly.
Next turn off all the layers so all you see is the image and your points. We will now begin to georeference the image. Using the Move tool in the georeferencing toolbar move the image so it lines up with your points. It may be a bit off as far as zoom is concerned but thats ok for now. Just orient the image so it is square with the points.
Using the Add Control Point tool start to match your image to your points. First you click on the aerial image where your point originated in Google Earth (In this example I will be using a railroad overpass that I spotted earlier as a landmark). Drag your mouse from there to the point in ArcGIS that corresponds to it. Your image will shift and the point should be on top of your image in the correct place.
Repeat this process for each point on your aerial until all points are matched up. You may have a small amount of residual, just play around with it until you feel comfortable with the outcome.
Once you have finished georeferencing the image click on the Georeferencing toolbar and click "Update Georeferencing". Next click "Delete Control Points". At this point your crosshairs will disappear. Your image is now georeferenced. If you look in the folder where your image is stored you will see several new files that are used to display the image in ArcMap.
Comments
Re: Georeferencing Images from Google Earth
Nice. Now find me a good freeware GIS program and I'll be set to go. [sigh] I miss ArcGIS.
Posted by:
Matt
at January 13, 2006 09:18
Re: Georeferencing Images from Google Earth
Hey Brady, sorry I got a question, i was surfing around and got to you Googlemap DIY GPS tracking and I thought you might be able to help me. Im trying to some how take Video and Audio Analyzations to emulate GPS coordinates and map them out through Googlemaps, thought you might have some ideas on how to do this, I've been doing some stuff with maxmsp but can't figure a way to output a gps coord to google, if ya got any ideas toss me an email, thank dude. Like ur blog!
Posted by:
Tyler Johnson
at February 13, 2006 12:43
Re: Georeferencing Images from Google Earth
I found your page while googling for how to "import photoshop image into arcmap". It would have taken me hours to dig this information out of the ArcMap manual, but you made it so clear and simple. Thanks!
Posted by:
Eric Sadoyama
at March 21, 2006 14:41
Re: Georeferencing Images from Google Earth
I was looking how to georeference an image from Google Earth with a GIS package. I found your page, it was very useful.
Thanks
Posted by:
Leslie
at July 04, 2007 16:48
Re: Georeferencing Images from Google Earth
I posted a pretty easy way to do this on the ESRI forums using the Lat/Long grid in GoogleEarth.
I think it's more efficient than your method.
http://forums.esri.com/Thread.asp?c=93&f=1740&t=193459&mc=2#msgid687378
Posted by:
Nico Tripcevich
at August 20, 2007 18:17
Re: Georeferencing Images from Google Earth
Worked fantastic! Thanks for posting it.
Had a little trouble getting the fit to display to show up but when I started a new mxd it was okay.
Posted by:
dove1234
at October 18, 2007 10:25
Re: Georeferencing Images from Google Earth
Hello Brady!
Great tutorial! I needed help regarding georeferencing my image and this walk through solved the issue.
Thanks!
Posted by:
Ehtisham-ul-Haq
at November 09, 2007 01:32
Re: Georeferencing Images from Google Earth
If you are looking for an OpenSource application to georeference photos, check out QGIS or gvSIG.
Posted by:
David
at December 18, 2007 21:06
Re: Georeferencing Images from Google Earth
It really doesn't work... I didnt get the expected outcome the image got a lot distorted when adjusting points... lots of time wasted thanks anyway if someone has a better way pls let me know
Posted by:
christian
at August 17, 2008 12:55
Re: Georeferencing Images from Google Earth
thinxxx a lot
i've been looking for such a tuto long time
n now i'm proud 2 work with arcgis
Posted by:
djamel messadi
at October 13, 2008 10:10
Re: Georeferencing Images from Google Earth
BEIJING, Nov. 19, according to Xinhua Taiwan's "Today" reported that Chen Shui-bian's four-day fasting guard for medical treatment, including the Oriental Hospital and the Panchiao to spend a wow power leveling total of nearly 20,000 yuan (NT, the same below) medical wow powerleveling expenses, as His health insurance card to stay in Taipei Detention Center, must first serve their own expense, the medical expenses from his detention in custody of the gold deduction, but Chen Shui-bian's custody, only 16,000 yuan deposit, the deduction is not enough, said the detention center, not powerleveling part of the Will be asked to make up for the families or lawyers.
1 At about noon today, Chen power leveling Shui-bian ambulance ride to live for three days to leave the county medical Panchiao District Court, although the people left, but still have to pay money, including an ambulance referral to spend 800 yuan, into the ring adhere to the intensive care unit Fasting only saline water wow gold and glucose, a day to spend about 1500 yuan, plus medical expenses, hospital fees, in Panchiao hospital guard spent a total of three million yuan.
Chen Shui-bian from the 16 guard for medical treatment, 17, from Yadong to wow gold Itabashi Hospital, because of his health insurance card on the detention center, the first day of the Far Eastern Memorial Hospital linked to the emergency room, registration fees, inspection fees, medical expenses, ambulance It took on the cost of 9500 yuan. After World of Warcraft gold the transfer plus the cost of the nearly 20,000 guard of medical expenses, the Taipei Detention Center will take custody of people to deduct, in other words, Chen Shui-bian have to foot the bill themselves.
Posted by:
wow power leveling
at November 19, 2008 19:05
None
Post a comment
