Preview Cartographica 1.5:New Georeferencing

This is the fifth follow-up to Onward to 1.5 documenting the move to the 1.5 release.

It's taken a bit of time to get to this development release (d17), but that's because I've been working on an oft-requested improvement for Raster fans. In this case, it's a new Georeferencing system. It's not completely finished yet (development version, remember), but the bulk of it is in and solid, and I'd appreciate feedback from anyone who works with Georeferencing Raster images.

I'm leaving the existing Georeference Editor (located in the Edit > Georeference… menu) in place for the time being, and they work pretty well together. However, I expect the new tool will likely take over for the old one going forward.

The new Georeference tool (select the Raster layer in the Layer Stack and choose Tools > Georeference Raster…).

I'll be working on the documentation on this soon, but the basics should be pretty straightforward. A new window is created that has the reference view on the left (your current map without the layer to be georeferenced) and the working view on the right (the selected Raster layer).

Unlike the previous version (still available as mentioned above, for now), this georeferencing tool does not try to overlay the images during the process. Instead, it provides you a straightforward way (option-click) to add Ground Control Points (GCPs) to your working view and to the reference view. Once you close the georeference window, these GCPs are applied to the image (using the Map Projection as the reference coordinate system) and then shown on your map. If you don't like where it ends up, use Edit > Undo to reverse your changes, or use the Georeference Raster tool again to make modifications.

A few things to note about this version (if you're reading this after the release, please look for an updated version of this entry):

  1. You need to have at least 4 GCPs to even begin to have the match look good.
  2. The more spread out the GCPs are, the better the fit will be to the underlying image.
  3. If you want to georeference in a specific coordinate system, set the Map Projection before starting your georeference for the best results.
  4. Live maps are often a good georeference frame, but if you want more visible room around the loaded map (for example, if you load only the image to be georeferenced and a live map layer into your map before using the command), just zoom out in the reference pane.
  5. The Georeference window beings in Edit mode, but can be changed to Zoom or Pan mode through command keys or menus. If you do this, you will need to choose the Select mode in order to edit the GCPs.
  6. Keyboard arrows are available to move the currently active GCP in the active pane.
  7. You can toggle between panes using the Tab and Shift-Tab keys.

Known Issues:

  1. Make sure that each GCP on the left corresponds to a GCP on the right. If one side is missing, d17 will allow you to commit the edit, which results in a really bizarre mapping through the zero point of the Map CRS. Don't worry, you can go back into the Georeference Raster window and edit this out. Just look for the GCP without a matching number on the other side.

  2. There is currently no way to Remove a GCP from both sides.

  3. If there is a blank area exposed by an image that doesn't have a natural alpha channel, it will show up black on after the GCPs are edited. This happened in previous versions of Cartographica as well, but will be fixed before the release

Stay tuned for the next development release as we continue the march toward the 1.5 beta and release!

Test versions

Today we're releasing the next development test version. This is not for the faint of heart. The development test versions are available by changing your Preferences to point at the Development feed.

Be warned that there will be bugs in the Development version and you should never use it on crucial files or files that are not sufficiently backed up.

If you're concerned about this, please wait until we announce the first beta.


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