Remote Sensing Tools

In Parts 1, 2, and 3 of this series — we discussed how software and utilities specific to working with geospatial imagery allow us to work-around the incompatibilities with popular image editors that do not support geospatial formats. However, there is a unique plugin that’s been designed for Adobe® Photoshop® to give users the ability to have most of the necessary functions of a GIS program within the Photoshop work environment. And aside from its capability of fully supporting the Geotiff format, another attractive asset is that it’s available to both Windows and Mac users.

Avenza Systems’ Geographic Imager plugin for Photoshop, is built on the Blue Marble geospatial development platform. It’s an incredibly robust application that allows any user of Photoshop to import, edit, reproject, georeference, mosaic, resize, and crop geospatial imagery — without the threat of any of the geospatial metadata being lost.

This could potentially be considered one of the most revolutionary plugins to be developed for Photoshop in years, as it truly bridges the gap between industry standard methodologies in the image editing world, and the geospatial industry which lacks the sophisticated editing tools and processing capabilities commonly associated with Adobe’s family of software. Both industries have a great deal in common, as they both rely on the same fundamental image processing principles, but the lack of geospatial format support in most image editors has previously created an interesting amount of criticsm or debate in their use.

The following, and final tutorial will walk a user through how Geographic Imager works with Geotiff .tif images — including common preferences settings and simple demonstrations to introduce its capabilities.

Prerequisites

Once again, if you require a sample Geotiff image, you may download the example I’ve provided here:
Sample Geotiff (~350 KB download, .zip format)

Preparing Geographic Imager

Once the plugin is installed into the Photoshop Plug-Ins directory, calling the Geographic Imager interface pallet is simple. Do the following to open the pallet into the Photoshop work environment:

• File → Automate → Geographic Imager…

That’s it! The pallet should have opened within the work environment, ready for use. But, now we want to take a look at the preferences and determine if we wish to make any changes. Geographic Imager has made this easy for us as well. Simply do the following to open the preferences dialogue from the pallet:

1. Click the fly-out options menu button at the top-right of the pallet, indicated by an arrow. The fly-out options menu will appear.
2. Mouse down to the Preferences option and click to open the dialogue.
   (Refer to the first image provided for steps 1 and 2.)
3. You can decide here how you wish to handle Reference Files, although it may not be necessary that any changes be made. In this example, I want to make sure the Use GeoTIFF for referencing by default option is checked to override the Reference Files options above, and to demonstrate that these options are available.
   (Refer to the second image provided for a visual example.)
4. Click OK, and your preferences will be set and saved for any later session in Photoshop, or until you change those preferences.

Opening a Geotiff in Geographic Imager

Opening a Geotiff image in Geographic Imager is like opening any other .tif image. Simply do the following:

• File → Open (or Open As…) → Browse to where your Geotiff .tif image is stored and open it.

It’ll take a couple seconds for Geographic Imager to read the georeferencing data included in the metadata of the image. Once that’s fully loaded, you’ll notice that the metadata is now viewable in the Geographic Imager pallet, with the reference file being the actual Geotiff image loaded.

Editing a Geotiff in Geographic Imager

Now that a Geotiff image is loaded into Photoshop, and the metadata has been read by Geographic Imager, we can edit the image in various ways that we couldn’t without this plugin. As a simple demonstration of what Geographic Imager allows the user to do, we’ll try two simple functions — resizing, and cropping.

Resizing

With Geographic Imager, resizing an image is no different than a user normally would in Photoshop. Simply go to the Resize editing function and type in a size. In this example, I’ll resize my sample_geotiff.tif image to 50% of the original and see what happens.

The first image to the right demonstrates that even though I’ve resized the image, the georeferencing has been recalculated by Geographic Imager, and the proper spatial resolution adjusted.

Cropping

Cropping is the same as well, except that now Geographic Imager has calculated and adjusted the coordinates to the pixels specified by the Crop tool, and the spatial resolution has remained the same.

(See the second image to the right for a visual example.)

Saving a Geotiff in Geographic Imager

Geographic Imager allows the user to save a Geotiff .tif image out of Photoshop in the same way that a standard .tif image is saved, except that it writes the Geotiff metadata tags in the header of the file. This is the support that Photoshop lacked, and that this unique plugin provides.

Save your edited Geotiff .tif file out of Photoshop, and append the name with a _ps at the end of the filename to see what happens. The new appended name of your Geotiff .tif image will now automatically appear in the Geographic Imager pallet as your Reference File.

(See the reference image to the right for a visual example.)

Caveats

Geographic Imager provides an extremely powerful new range of tools and functions in the Adobe Photoshop work environment, to meet a need that exists from the geospatial and cartographic community. However, as with most things technological, there are some minor drawbacks to consider.

• Geographic Imager currently does not support Photoshop’s internal scripting engine, which provides the use of Scripts and Actions for automation. This actually has little to do with Avenza, as the Adobe Photoshop SDK doesn’t provide access to this part of Photoshop’s core API. A user can, however, potentially automate simple pixel-based processing tasks as long as resizing, cropping, or other processes that Geographic Imager commands aren’t attempted in a Script or Action. There does remain a risk of damaging the georeferencing if automations are used, so it is not recommended.
• The Split Channels and Merge Channels functions are also not supported in the current version of Geographic Imager.
• Photoshop is a program that requires a great deal of memory to function efficiently. Although there are preferences that can be set to optimize processing and speed, or allow for larger file sizes, remote sensed imagery is still rather large and can be process-intensive in the Photoshop environment. Very large mosaics may not be possible in Geographic Imager without a modern, fast computer system to run these programs — and with a considerable amount of storage to allow for additional speed and processing enhancements.

Advantages

The advantages to working with Geographic Imager in the Photoshop environment is self evident, as it allows for the capability to edit geospatial imagery without the threat of losing vital metadata, or having to use additional utilities, potentially saving steps in processing and organization.

Additional considerations, are in relation to incorporating all the tools mentioned throughout this series — and the nearly limitless possibilities that can be gained depending on project needs. One only needs to imagine the advantages to a work-flow being organized and executed in a way that counters the demands that any project might require, and what methodologies or enhancements could be applied to create an individual or cross-organizational work-flow utilizing these tools. There may also be considerable cost advantages, depending on the needs of each project, hardware and software accessibility — and depending on what tasks can be allocated to any aspect of the work-flow. Or, perhaps an individual or an organization has more specific requirements for geospatial imagery production that demands a more specialized approach to other alternatives.

For More Information

For more information on the plugin mentioned in this part of this series, visit the developer’s Web site at the following address:

Avenza Systems, Inc.
http://www.avenza.com

Geographic Imager
http://www.avenza.com/products.geographicimager.html

In Conclusion

By providing this series, I’m hopeful that it represents an introduction to a wide range of possibilities to anyone interested in working with remotely sensed imagery with a set of relatively affordable, yet powerful programs. Depending on what needs may be within an individual’s or organization’s work-flow, anyone can basically benefit from the incorporation of working with geospatial imagery in the Photoshop environment, or similar tools.

The cost-effectiveness associated with many of the tools available also allows for a wider range of interest, not only for the professional, but for the hobbyist; and even greater reaching — the next generation of our future geologists, engineers, and cartographers. Anyone can expand on something as simple as learning some basics of how to use these tools to establish a foundation for additional learning, and that could potentially become a career objective, or spark a passion and interest in the Remote Sensing and GIS sciences and production fields. Making the tools and information that anyone needs to begin, be accessible and intuative enough that they might get started, is — in my opinion — a critical enhancement toward sparking such interests and passions. And I do hope that anyone might agree.