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markus_mouse1 post(s)
#02-Mar-17 10:13

Hopefully an easy one. I am trying to register JPG and PNG images.

I create a blank control point map, as per the user guide, import a table of points, create a drawing; all looks great.

I import and open (make active) the JPG drawing, but nothing I can do will make the 'Register' button in the control points panel active!

Both the Control Points drawing and the imported image are set as WGS84 projection...

What am I doing dumb?

Dimitri

4,025 post(s)
#02-Mar-17 11:13

Need more details...

I create a blank control point map, as per the user guide, import a table of points, create a drawing; all looks great.

blank control point map... not sure what you mean by this. "control point map" I don't recall being a term in the user manual. Do you mean a blank map with no layers?

as per the user guide... what topic?

import a table of points... what table? Importing a table of points is not creating control points as in adding them one by one.

If you are trying to duplicate a topic in the user manual, which one is it?

ColinD


1,784 post(s)
#02-Mar-17 20:04

Perhaps you have missed this step

3. Place control points in the drawing at locations corresponding to those used for control points in the image

http://www.georeference.org/doc/georegistering_an_image_to_a_drawing.htm

So you should have a set of control points on your points drawing and a set on the equivalent locations on your image.


Aussie Nature Shots

scandalxk53 post(s)
#03-Mar-17 14:35

In fact, you don't actually say that you have created any control points at all!

To register the image, you need to have control points at known co-ordinates in a drawing; and equivalent control points in the image.

If you have imported a table of known locations and created a drawing from it, then probably you now have a drawing containing some point features. Point features and control points are not the same thing. However, you can use the point features to make control points, like this: open the drawing, and open the Control Points pane (View - Panes - Control Points). Select Snap to Points in the snap toolbar. Select New Control Point in the Control Points pane, and place a control point on each of the point features in the drawing. They will be named Control Point, Control Point 2, Control Point 3...

Now open your image, deselect Snap to Points, and place control points in the image at equivalent locations to those in the drawing. Make sure you do it in the same order so that the points have the correct equivalent names (although you can rename them in the Control Points pane if you go wrong).

Now, with the image active, press the Register button in the Control Points pane, select the control points drawing to register it to, and Bob's your uncle.

E&OE

tonyw
380 post(s)
#06-Mar-17 05:20

Markus, try the attached example map. It's setup with control points and you can press the Register button to make the magic happen. I use Vancouver BC as the example map (making a pitch for a future Manifold user's meeting, ahem).

To get the workspace layout shown in the attached screen shot, open the two images in the .map file: a) Vancouver BC georeferenced basemap UTM9 (a georefernced TIFF image) and b) Non-georeferenced image which was a screen shot from Google maps. The georeferenced basemap is the reference to which the non-georegistered image will be stretched to match. To get the same layout as in the screenshot, click on image Vancouver BC Georeferenced basemap to give it the focus. Then on the menu, click Window > Tile vertically. You should have what the screenshot shows, georeferenced on the left, non-georeferenced on the right as in the screenshot.

With the View > Panes >Control points pane active, you should see the five control points I've already made. You can add other control points. It doesn't matter which image you start with. Pick a prominent landmark that appears in both images. In this instance I used points of islands, where major highways have a corner, where there are unambiguous intersections, whatever I can find that's unambiguous. There is a correspondence between control points between the non-georeferenced image and the georeferenced basemap component. Create a control point in one image and create a corresponding control point in the other image. The incoming non-georeferenced image will be stretched until its control points coincide with the control points on the reference map. I find about 4-5 well distributed control points is sufficient but go ahead and add some more to try it out.

Do the magic. Click on the non-georeferenced image to give it the focus. In the control panel pane, click on the Register icon. In the Register dialog box, confirm that the reference is the georeferenced basemap. Click OK to register the Google map screenshot.

Create a map of the two images, make the just-georeferenced map the top layer, it should lie correctly over the basemap.

If you have a drawing made from a table of points, you'll need to be able to find and make control points in the incoming JPEG image that match the points from your table. Sometimes this is not easy. Sometimes I have surveyor's drawings that are over 100 years old that do not have modern roads and any rivers have changed their channels. In that case there are very few common points between the incoming image and my georeferenced map.

Attachments:
Example of georeferencing.map
Screenshot of georeferencing.JPG

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