Monday, March 30, 2009

North Korean Missile Site Images

CNN ran an article today showing a DigitalGlobe image of the Musudan-Ri missile site.  The article is based on a report from the "Institute for Science and International Security," which has a number of related reports on their web-site.  The latest report contains annotated time sequence of both GeoEye and DigitalGlobe shots of the launch pad (DG images below):

March 24, 2009

March 27, 2009

Clearly things have changed at the site between images, but it is difficult to discern whether or not the rocket is on the launch pad or not.  The red circle depicts where the top of the missile should be.  

Thursday, March 26, 2009

Leica RCD100 Medium-Format Mapping Camera Released

The latest news from Leica Geosystems is the release of the RCD100 medium-format mapping camera.  If the name sounds familiar, that's because the RCD105 for the ALS was just released last year.  While the RCD105 is a solution for LIDAR sensor owners pursuing fused imagery/LIDAR workflows, the new RCD100 is a comprehensive stand-alone system for orthophoto and mapping projects (orthos, terrain, 3D feature extraction, etc).  

This means the RCD100 camera system can flown standalone for workflows like this example, which is actually based on RCD105 imagery.    

Tuesday, March 24, 2009

Processing GeoEye-1 GeoStereo Imagery in LPS

I mentioned last week that I would outline the workflow steps in LPS for creating terrain, orthophotos, and 3D vector data from GeoEye-1 GeoStereo imagery.

GeoEye-1 has both panchromatic (0.41 meter resolution) and multispectral (1.65 meter resolution) sensors, and I performed the processing with the panchromatic data because it is higher resolution. For this particular project I have RPC imagery (a single stereo pair) along with surveyed ground control points. Although the imagery is lower resolution than most airborne photography, one of the big benefits is that the image footprint is much bigger - this can dramatically decrease time and effort for certain parts of the workflow (e.g. mosaic seam editing).

In LPS the processing is straightforward: set up the project > measure ground control points > run automatic point measurement > perform the bundle adjustment > generate and edit terrain > perform orthorectification. 3D feature extraction can come anytime after the bundle adjustment is performed. What follows is an overview of the workflow. I won't go into the minute details but will cover the major workflow steps.

Block (project) setup is easy: just choose the model (GeoEye RPC) and then add the images in the LPS Project Manager. At this point processes like image pyramid generation can be performed as well.

A GeoEye-1 project in the LPS Project Manager

After the block is setup, the next step is to use point measurement in either stereo or mono mode to measure the ground control points. This is where we relate file/pixel coordinates with real-world XYZ coordinates from the GCPs. Typically this can be a time-consuming step but LPS has an "automatic XY drive" capability that puts you in the approximate area when you're ready to measure a point. After the GCPs are measured automatic tie point measurement can be run, which will generate tie points. Users have full control over the tie point pattern so there is a high degree of flexibility. After generating tie points, bundle adjustment can be performed in LPS Core. I won't delve into too much detail here, but this process involves running an adjustment, reviewing the results, refining if necessary, and then accepting the results once they are suitable. This is a critical step, because after triangulation we have our first data product: a stereo pair. Stereo pairs are crucial for 3D product generation, because XYZ measurements can be made from them. That means 3D terrain products and vector layers can now be generated.

Viewing a control point in stereo

The next step is to generate a terrain layer that can be used as a source during orthorectification, and may also be used as a product in it's own right. The Automatic Terrain Extraction tool in LPS can generate a surface and allow a high degree of control with regards to post spacing, filtering, smoothing, and more. In this example I used it to generate a 5 meter IMG grid, displayed below.

Terrain displayed in ERDAS TITAN

After performing terrain editing to create a bare earth DEM, I created an orthophoto from one of the 0.5 meter panchromatic GeoEye images. Terrain editing (in stereo) is important because surface objects such as multi-story buildings can introduce error into orthophotos if they are included in the terrain source. The orthophoto is displayed below.

Digital orthophoto in ERDAS TITAN

With a 0.5 meter resolution, it is also possible to extract 3D features such as buildings. I collected a few in PRO600 and then exported them to KML for display in GoogleEarth.

3D KML Buildings in GE

Note that other tools (in this case Stereo Analyst for ERDAS IMAGINE) can also be used for 3D feature extraction. Here is a building collected as a 3D shapefile with texture applied. Note that this is not generic texture, but rather the actual texture from the pan GeoEye-1 imagery. While it doesn't cover all facades, it does add a level of realism that adds to a 3D scene.

In summary, the process for created value-added geospatial data products from GeoEye-1 GeoStereo imagery can be accomplished by following the steps identified above. In a relatively short period of time, an array of 3D products can be derived that have value in a number of different applications. It will be exciting to see what kinds of applications come out of GeoEye-1 stereo imagery in future months and years!

Monday, March 16, 2009

3D GIS and GeoEye-1 GeoStereo Imagery

The notion of "3D GIS" has been gaining momentum in the geospatial industry for a few years now.  Witness the recent seminar conducted by the Britsh Columbia URISA chapter: "The New Dimension in GIS - 3D Analysis".  If the topic interests you, abstracts and many of the full presentatiosns can be downloaded from the site.  A look at the topics shows an examination of digital cities, 3D models, BIM, LIDAR, digital orthophotos orthophotos and more.  The industry has been abuzz with the integration of GIS, photogrammetry, and remote sensing for some time now, but only recently have the data products and tools have matured to the point of making integrated 3D GIS applications a reality.

Satellite imagery providers that have stereo collection capabilities are a good example of the drive to generate 3D data products.  As I've commented previously, the lack of industry standards for photogrammetric metadata poses a challenge to offering stereo products - but this is changing with data vendors pushing stereo products forward and efforts at the OGC-level to drive standards. An interesting item from Matt Ball's summary of the recent ASPRS conference in Baltimore was the keynote presentation from John R.G. Townshend, "calling for the standardization of imagery metadata".

GeoEye packages their satellite imagery products in a few different categories: Geo, GeoProfessional, and GeoStereo.  As stated on the GeoStereo product page, "the RPC camera model supports block adjustment, three-dimensional stereo extraction, DEM generation, ortho-rectification, and other photogrammetric operations. "  

GeoEye-1 Stereo Imagery in LPS

The benefit of stereo imagery is the value-added geospatial information that can be derived from it.  The quote above relates three specific data products: digital orthophotos, terrain models, and 3D vector data (three-dimensional stereo extraction).  Digital orthophotos have become a standard component in base map data, and can be used for accuracy assessment (e.g. are the vector data layers complete and correct?), 2D vector digitizing and update, change detection, and a number of other applications.  Terrain data, which can be automatically generated, is a key component for orthophoto generation, and is useful for a wide variety of other applications as well. The other data product mentioned above is 3D vector data.  One of the major benefits of stereo imagery is the ability to measure objects in X, Y, and Z and collect 3D vector data.  Not only can the vector data be extracted in XYZ, but the objects can be accurately extruded down to the ground level.  This provides a 3D object that can then be attributed, textured, and then fed into a variety of applications.   

Since we recently received GeoEye-1 GeoStereo imagery for validation in LPS, I thought it would be worthwhile running through the workflow in LPS 9.3.1.  In the next post I will outline the workflow steps - with the right set of tools, developing the products outlined above is a very straightfword process!  

Sunday, March 15, 2009

Journal of Maps: Research-Based Maps Online

The Journal of Maps is an electronic publication dedicated to the publication of research-based maps.  Although a login is required, registration is completely free and one you are logged in your can access a number of research papers.

The journal features a worldKit-based interface that features research paper map extents displayed over a global map.  The site also provides the abiilty to view the map locations in Google Maps, displayed below (or see here).  

It is great to see a forum emerge for interactively browsing research papers by geographic areas as opposed to the more traditional approach of searching based on subject.  It should be interesting to see how the journal develops!

Wednesday, March 11, 2009

Photogrammetry Meets Kite Aerial Photography (KAP)

Kite Aerial Photography, as the name suggests, involves rigging a camera up to a kite system and then using it to take aerial photographs. After seeing my previous post on photogrammetry with a camera attached to a helium-balloon, Dr. Mike Smith at Kingston University contacted me about research he has been conducting in the realm of KAP and photogrammetry. Along with Drs. Chandler and Rose, he recently published a paper in Earth Surface Processes and Landforms entitled "High spatial resolution data acquisition for the geosciences: kite aerial photography".

The paper is relevant for the mapping industry because it provides an overview of the aerial acquisition process, the photogrammetric processing, and then an accuracy assessment of the results. I'll start with the results: their methodology enabled the production of stereo pairs, digital elevation models, and stereo imagery. Furthermore, the stereo imagery was triangulated with an accuracy of roughly 10mm in planform against surveyed ground control points.

The methodology involved using a 6 megapixel Nikon D70 camera and collecting aerial photography at altitudes of up to 200 meters over three test sites in the UK. GCP targets and XYZ samplings for topographic modeling were measured with Leica Geosystems TPS1200 and TCA 1105 Total Stations.

All the photogrammetric processing was performed in LPS. This involved setting up an LPS Blockfile (a project file), adding the images, and subsequently running through the aerial triangulation process in LPS Core in order to produce stereo pairs. With oriented images, the LPS Automatic Terrain Extraction module could be used to generate a digital elevation model. Next, the oriented images along with the digital terrain could be used to produce digital orthophotos. The paper describes the process in a high level of detail, as well as an excellent evaluation and discussion of the results.

Here is an image of an orthophoto superimposed with terrain points (red = automatically extracted, blue = measured via total station):

And here is a perspective view of an orthophoto draped over a corresponding digital elevation model, with contours:
In my opinion it is a great looking product considering it was generated with a 6 megapixel SLR camera flown from a kite!!

So why is this relevant for the mapping business?

The study illustrates a great low-cost approach to localized (as opposed to wide area) mapping, which means it may very well be a viable option for applications ranging from mapping cultural heritage sites to localized studies on soil erosion and other environmental and natural resource mapping projects. It is significant because it represents a significant cost saving over the traditional helicopter-based approach. If I had any talent for flying big kites I'd give it a whirl, but for now I'll leave it to he pro's...

Sunday, March 8, 2009

Update: Photogrammetry at the Acropolis

Last July I stumbled across a laser scanning and photogrammetry operation during a visit to the Acropolis in Athens, Greece. As discussed here, the project involved terrestrial laser scanning coupled with aerial photogrammetry. A unique aspect of the project is that airspace restrictions over the Acropolis meant that imagery could not be collected by motorized aircraft (e.g. helicopter), so the project team rigged up a balloon system instead. Here's a picture of the balloon and camera in flight:

A paper describing the data collection and processing process is now available online here. The paper is an excellent resource for those interested in digital preservation of cultural heritage sites, and also outlines how complementary photogrammetry and laser scanning are for 3D data generation. As is the case with many photogrammetric projects, the digital orthophotos derived from the aerial photographs will ultimately reside in a GIS.

Wednesday, March 4, 2009

Sensor Spotlight: GeoEye-1

With all the recent news about NGA certification for GeoEye-1, I thought I'd write a post on it. Aside from usage in Google Earth, there's also been recent coverage on GeoEye imagery being used in a new video game from Ubisoft. Check out the YouTube video of the game below. There's an interesting dialog about using stereo imagery for gaming as well, which makes sense considering terrain, buildings, and image texture can all be derived from the GeoEye stereo products.

As for the details, sensor specs are available on the GeoEye website here. The pan sensor has a resolution of 0.41 meters and the multispectral sensor has 1.65 meter resolution. The swath width is 15.2 kilometers and at an altitude of 681km the revisit time is less than three days. GeoEye also maintains a great looking gallery of images from the sensor here.

Back in September I discussed the launch site set-up by GeoEye for streaming video of the launch. This is now available on YouTube as well:

We added support in LPS for the GeoEye-1 rigorous and RPC sensor models back in LPS 9.2, and it is also available in the current 9.3 version. GeoEye has also recently provided us with sample data for accuracy testing and validation. Early results are looking good and I will post an update when we're a bit further along.

Monday, March 2, 2009

A Look at the Open Topography Portal

It was announced in early December, but I just recently came across the Open Topography Portal. The portal has made a large amount of LIDAR data available for active fault areas in both California and Washington. One of the unique aspects of the portal is that it provides web-based tools for processing raw point cloud data prior to download. The download interface is fairly slick, featuring a Google Maps interface allowing you to interactively select an area and then returning the number of points in your selection (guest downloads are limited to under 50 million points). The system displays the bounding coordinates and then allows for the definition of the delivery format.

The portal provides access to standard DEM products, (e.g. filtered bare earth), point clouds, as well as customized DEMs. Here are some of the options for creating a custom download:

Based on the selection area and processing options, the system provides the estimated processing time and then sends an email when the job is complete and ready for download.

I selected a small area and downloaded the point cloud data, which I then imported into ERDAS IMAGINE and created a shaded relief. Here's what it looks like (note that vegetation and buildings are all included, as filtering has not been applied):

Personally I think the user experience of the Open Topography Portal is more intuitive than the broader USGS CLICK (Center for LIDAR Information Coordination and Knowledge) portal. However portals are developing all the time and it is good to see progress in the ease of use and accessibility of advanced processing and download options.

The other notable news regarding the Open Topography Portal concerns the San Diego Supercomputer Center (SDSC) starting cloud computing research - with a special focus on the GEON LIDAR workflow application. This is something to keep an eye on, as LIDAR data is massive and as of yet I haven't heard of any attempts to use cloud-computing for processing or data management - although there have been initiatives in terms of storing LIDAR data in a database (e.g. the folks at LASERDATA use PostGIS). The Open Topography Portal is a collaboration between scientists at the SDSC and earth scientists at Arizona State University.