Sizing Images for Ghost It

BrianZ's Golf Course Design Resource

Sizing Images for Ghost It

Ghost It is a transparency program used to make the window your image is in transparent. By laying your image over the top of the course architect program, you can then trace the shapes for your fairways and greens. You can download Ghost It here.

When using Ghost It the scale of the image must match the zoom level in the course architect. This doesn't matter for Terrain Assist because it automatically fits the images to the plot.

First you have to find out what resolution your imagery is at so you can match it with the scale of the course architect view. The USGS images tell you what resolution they are at when you download them. It is usually given in meters per pixels.

DRG = 1.0 meters/pixel
DOQQ = 1.0 meters/pixel
Orthoimagery = 0.3 meters/pixel
Google Earth/Microsoft Virtual Earth = Varies

The Google Earth and Microsoft Virtual Earth imagery varies and does not tell you its resolution. To find it:

Use the scale in bottom left or bottom right corner of the image to count the number of pixels for a given length in meters.
Divide the length in meters by the number of pixels.

Use the Zoom Cancel button to get a consistent zoom level in the course architect. This always sets the zoom level of the window to 2,117 meters (2,306 yards) wide. The scale of the course architect view differs depending on the size of the window.

Maximize the course architect window so it fills the screen.
Divide 2117 by the pixel width of your screen.
- For example: 2117 / 1024 = 2.067 meters/pixel.
Now divide the resolution of the image by the course architect view resolution above.
- In this case for the DOQQ 1.0 / 2.067 = 0.4837 or 48.37%.

This is the size you need to view the image so it matches the course architect view on zoom cancel. Each time you zoom in you need to double this number. To make zooming easier, resize the image so that one of the zoom levels lands on 100%.

Find the zoom level closest to 100%.
Resize the image so that this zoom level is the same as 100% image size.
- In this case zooming in once requires ~97% image size.
- Resizing the image by 103% gives you easy zoom levels to remember:
  - Zoom Cancel = 50%
  - +1 Zoom = 100%
  - +2 Zoom = 200%
  - +3 Zoom = 400%
  - +4 Zoom = 800%

When you use the zoom out button it does not cut the view by half, it cuts it by 1/3. You have to divide the percentage you are currently at by 3 to find the correct zoom level when using this button. For that reason I recommend you always use zoom cancel when you need to zoom out.

Repeat the process above for all of the images you want to use with Ghost It.

If you used your images with Terrain Assist then they have all been cropped in the same place and you do not need to repeat the process above. Instead you can do the following:

Resize the image above again by 200%, 400%, etc. until the pixel size is closest to the highest resolution image you have. This keeps the easy zoom sizes without having to reduce higher resolution images too much.
Resize all of the other images to match the pixel size of the resized image. The images may be a few pixels off in proportion but close enough that it isn't a problem.

If you want you can put all of your images on different layers in a Photoshop or Paint Shop Pro file. This makes it really simple to switch between images while working. All you need to do is hide the current layer and make a different layer visible.

Once you have your images sized correctly you can use them with Ghost It.

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