How to create a World File

In continuing effort of my last blog post, I will explain how you can create a simple world file to use with an image which is not georeferenced to use with AutoCAD MAP, Civil 3D and/or InfraWorks.

In my previous blog post “How to grab aerial images from WMS server” you have made a rectangle (or square) as the boundary to your project of where you want to download an aerial image from a WMS server.

Now I will use the same example to write down the coordinates of the upper left corner of that rectangle (or square). Now use the half of the value of the factor I have calculated back then (which is in fact the ground resolution of that particular image) and add this value to the X ordinate, and subtract the same value from the Y ordinate. The result will be used as the coordinates for the World File which in return will be used as the insertion point of the aerial image map.

Now create a text file with the following content (6 rules):

[calculated factor]
0.0000000
0.0000000
-[calculated factor]
X (value = UpperLeft X ordinate plus half the value of the calculated factor)
Y (value = UpperLeft Y ordinate minus half the value of the calculated factor)

If I use the same URL example from my previous blog, 

http://geodata1.nationaalgeoregister.nl/luchtfoto/wms?LAYERS=luchtfoto&FORMAT=image%2Fjpeg&VERSION=1.1.1&REQUEST=GetMap&STYLES=&SRS=EPSG%3A28992&BBOX=208670.623,375465.3687,209670.623,375965.3687&WIDTH=2000&HEIGHT=1000

the content of my World File will be as follows:

0.500
0.000
0.000
-0.500
208670.873
375965.1187

Save the file with the same name as the image you have downloaded from the WMS server but with the file extension built as follows:

If your image has the jpg file extension, use jgw as the file extension for the World File.  You can name any bitmap file extension by omitting the 2nd (or middle) character and by shifting the 3rd (or last) character to the left and finally by adding the ‘w’ character to the end. So ecw would become eww and png  would become pgw, etc.

You can also download the file here.

Now you can use both files, the downloaded aerial image with the self made World File in AutoCAD Map / Civil 3D or InfraWorks. You may even use these files in vanilla AutoCAD if you like, by using this free available tool: GeoRefInsert from the Autodesk Exchange Apps store. 

In my next blog post I will explain how you can successfully use a GDAL WMS XML file to use with InfraWorks.

Happy georeferencing! 😃