Layers are separate images which contain different information from the same area and which you want to merge into a single image showing everything at once.
You can load as many as you wish.
The image on to which all the other images will be superimposed is called the background or zero layer. A background layer image is chosen by clicking on it in a normal AirPhoto window before choosing the layers option so that it gets the Windows focus.
All images and maps for layering on the background must be calibrated and aligned to the same chosen grid and cropped after alignment to remove any white space which surrounds them. Failure to do this may cause the automatic placement and resizing used in the layering function to place the layer incorrectly.
If no files have been loaded, click on layers to load multiple images to superimpose as layers.
After two calibrated files which may be either images or maps have been loaded, clicking on Layers on the main menu
brings up a special window which enables manipulation of the positions, size and orientation of the images with respect to each other.
You can also open the Layers Window and load images using the Open entry on the File menu. If you are working with a map and an image or images, load the map first so that it becomes the background layer.
A layer is made "active" from the control panel at the right side of the screen by clicking on it there. In the main layer window, zooming in or out with the mouse wheel and moving the collection of images up, down or to the right or left should be done with the scroll bars. The layer which has the focus is surrounded by a red box with drag handles. This layer can be moved separately to locate it precisely in case the automatic placement method used requires a small correction. Place the mouse on the cross cursor at it's centre, hold down the left button and drag. You can also change the size of the layer which has the surrounding red box by dragging on one of the round points with green centres. This can be done separately for the top, bottom and sides.
You can change the order of the layers with the Up and Down buttons. You can also add, insert or delete a layer with the respective buttons, and you can rotate a single layer with the rotate button. A number of general properties for a selected layer can be applied using the tabbed dialogue box. The special effects page permits changing the transparency of the selected layer as well as applying a large number of effects to it relative to the background layer. These can be seen by clicking on the down arrow of the Operation Combo Box.
Try the different effects to see what they all do. You can also zoom in or out of the chosen layer separately from the zoom available with the mouse wheel in the main window using the Magnification slider on the Magnify layer tab.
The most useful options are MIN (Darken) or MAX (Lighten):
If you have a black and white map as the zero layer and a coloured image, e.g. Google Earth, you can have the map superimposed on the GE image without the loss of colour saturation that otherwise occurs when you increase the transparency of the overlying GE image.
When you have obtained the appearance you want, you can either merge all the layers into a single image which can then be saved using the Save merged layers option from the File menu,
or you can save a special file with the extension lyr that permits you to start again if you wish from the main menu in AirPhoto with no images loaded. When the layer window opens, choose the Load option and enter the name of the special file.
You can also open any uncalibrated image with the Open image option of the file menu which will then be loaded as a layer with it's upper left corner at the upper left corner of the screen and you can save it as well.
The layer image shown above was obtained with the following steps:
1) Select a national or international grid.
2) Download a Google Earth image from the area of interest using the AirPhoto Import Google Earth option.
3) Download a second GE image from an area nearby, perhaps which overlaps the first.
4) Exit GE import.
5) Both images are displayed. Align each to the chosen grid using the option on the main Grid menu. Save the resulting files under new names and close the GE original files. Crop to remove white space and save again.
6) Open the map image of the area of interest.
7) If not done previously, calibrate it and align it to the grid.
8) Make sure that the map has the focus by clicking on it.
9) Click on Layers on the main menu, and wait until the layering process opens the Layer Processing window.
10) Make whatever modifications are desired, merge the layers, save the merged layers to a newly named file and exit Layer Processing.
11) Open the merged layer file and from the Grid menu or the lower toolbar button, load the calibration from the background image file.
12) Save under a new name.
If the background is a black on white map:
1) Open the map which must be calibrated.
2) Change it's polarity to white on black using the Negative option on the AirPhoto lower toolbar after pressing the red arrow at the right to get the second set of tool bits if you want white lines on a coloured image.
3) Get coordinates for searching from the map by moving the cursor to a visible grid intersection and note them down.
4) Open GE in AirPhoto, click to expand it, click Parameters to get a 3 x or more enlargement, then use Find in Grid to go to the point chosen in the map by entering the coordinates and the map sheet in the form. You may load as many of these images as you wish even with adjacent areas of different dates if the Historical Imagery option was checked in the GE view menu.
5) Use SaveAs and GECloseExit.
6) Align the GE image to the Grid (very important).
7) Crop so that any visible white space around the image is removed. (Optional)
8) Click the top bar of the white on black map to give it the focus and then the Windows Tile button so that the GE result is visible again, but without the focus.
9) Click on Layers. The map will be shown as the background, the GE Image as the top layer.
10) Select Effects, Operation. Select MAX in the drop-down menu which will give you white map lines on the GE image.
Push the transparency slider to the extreme right for best contrast.
If you prefer black lines on the GE image, the background must be white. Then use the AND option.
11) Go to the Layers File menu and click Save Merged layers
and save to a new file.
12} Exit Layers and open the result:
The map background image should have a greater geographic area than that of the top layer image or images (in the example above from Google Earth). may extend outside the area of the map.
Open a set of multiple images, perhaps obtained by saving a sequence from Google Earth around a visible object with known geographic coordinates. The key shortcut if you prefer is Ctrl+O+Shift from the main menu before any files have been opened.
Select the images for layering:
When the layered images appear, click on the thumbnail image which shows the known point best:
Then click on the File menu entry "Merge and Save Layers" You will be prompted to enter a file name. The image will be written to the selected collection used for the layers.
Click the icon in the upper right corner to show the merged layer image in full screen mode:
Click on the main menu option to show the calibration points for this merged image and if desired, click on "Move Calibration" to show a magnifier with which you can drag the calibration point for the know object to overlay it precisely: