Manual georegistration of a component involves moving and re-scaling the component using manual techniques by manually editing the scale and positioning of the component. This is rarely done since the automated georegistration process is far easier to use. In some rare cases, manual georegistration as set forth herein may be used to "nudge" an image slightly that has already been positioned using the automated process.
For georegistration using manual methods an image must already be arranged in a pattern equivalent to some geographic projection. The two most frequently seen such arrangements are:
· Images showing the whole world or large sections thereof with pixels arranged in Latitude / Longitude projection.
· Images showing local, overhead views that may be taken to be in Orthographic projection.
Because Manifold imports all images from non-geographic formats into Orthographic projection, manually georegistering images showing local, overhead views in North-up orientation may be done by people willing to endure the tedium involved.
Manual Georegistration using Orthographic Projection
1. Import the target image into the project.
2. Import a reference drawing that has features in common with the target image.
3. Insert a map that includes the reference drawing.
4. Click open the map and note the approximate geographic center of the drawing.
5. Drag and drop the target image into the map. Position it in a layer beneath the drawing.
6. Click open the image in its own image window.
7. Open the Edit - Assign Projection dialog for the image. Change the Center Latitude and Center Longitude values to those measured as the center of the drawing. Press OK.
8. In the map window, the image will appear as a microscopic dot at the exact center latitude/longitude give above. Change the Local scale values for X and Y to rescale the image. Usually, the X and Y unit values should be the same and will be some fractional amount, such as one X or Y unit is .004 meters. Adjusting these values up and down in a trial and error fashion will quickly show which is the right direction to go.
9. Some images may also require a shift in Local offset in X and Y to move them sideways or up and down to match the drawing.
6. Right click on the image's layer tab and choose Register from the context menu.
7. Using directions like those given in the Maps - Register topic, change the X unit and Y unit values to rescale the image and also change the Easting and Northing properties to move the center of the image to the center of the map. This will prove incredibly tedious and frustrating. With larger images and Preview checked it will also be annoyingly slow to boot.
There are two options to the above procedure because there are two alternative methods after step 5. The net effect of the Register dialog is to change the coordinate properties of the image. These properties may also be edited directly in the Edit - Assign Projection dialog.
See the Manually Georegister an Image topic for an example. See the Edit - Change Projection dialog topic for more on advanced projection options such as Local scale.
For fine adjustment of registration, use the layer repositioning commands.
For certain expert uses it makes sense to use manual georegistration. For almost all other purposes, the automated georegistration process employing control points is far easier to use.
For brevity, this topic and other georegistration topics use images as examples. However, the same procedures apply when georegistering drawings or surfaces .