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.

Sensor Spotlight: CARTOSAT

Today's post will highlight the CARTOSAT-1 and CARTOSAT-2 sensors. CARTOSAT-1 was launched in 2005 and features two panchromatic cameras for stereo imagery capture. The cameras cover a 30 meter swath and the resolution is approximately three meters. Many of the sensor features and are located on the ISRO site here. For a good white paper on CARTOSAT-1, presented at the ISPRS conference in Beijing, see here. The authors outline the processing workflow for CARTOSAT-1 data in LPS, consisting of setting up the orientation, performing automatic terrain extraction, and finally orthorectifying the images. While the processing was performed on CARTOSAT-1 data, the workflow would also be very similar for CARTOSAT-2.
The paper highlights some software improvements we implemented between LPS 9.0 and 9.2 SP1, as some of the initial processing was performed in LPS 9.0. The improvements specifically pertained to the LPS ATE (Automatic Terrain Extraction) module, where we added quality improvements in the correlator. The authors found the ATE results with LPS 9.2 SP1 to be acceptable, with errors general under 2m. It is also important to note that we made Adaptive ATE available for satellite sensor models with the recent release of LPS 9.3, so I suspect the accuracy could even be further improved.

Here is another ISPRS paper from 2007 outlining some advances in CARTOSAT-1 data processing. It also highlights the use of LPS for the terrain processing component of the workflow.

CARTOSAT-2 was launched in early 2007 and also features two panchromatic sensors, featuring a greatly improved resolution of under one meter. A spec sheet from ISRO is here. The wikipedia article makes some interesting statements about resolution (80cm) and pricing, but I haven't been able to verify these statements. This paper, also from the ISPRS conference in Beijing, has some great information on both satellites, as well as some further details on the terrain processing workflow. LPS was used as well in this paper, although it does not state the version number.

Note that in addition to using LPS ATE for automatic terrain extraction, the LPS Terrain Editor can be used to view the imagery in stereo and perform interactive terrain editing (from manual compilation to editing an automatically correlated surface).
Note that in addition to the CARTOSAT-1 and 2 sensors, there is also a CARTOSAT-2a sensor that is reserved for military usa.

Sensor Spotlight: Leica Geosystems ADS80 Airborne Digital Sensor

I’ve touched on ADS40 sensor technology in a few different posts, but the focus of today is the new ADS80 sensor. The ADS80 is a pushbroom airborne sensor that was formally announced and highlighted at the ISPRS conference this past summer in Beijing.

See here for an interesting discussion on the transition to from analogue to digital processing as well as pushbroom sensors. The new sensor represents a solid advancement, and arguably delivers the best quality imagery of any of the commercial large-format airborne sensors.

But what is the difference between the ADS80 and the previous version, the ADS40? This post will cover the differences and explore some of the specific technical improvements.
Firstly, there are several overall design improvements. There is a new design for the data channel with overall data throughput increasing from 65 MB/s to 130MB/s. The fastest cycle time has increased from 800Hz to 1000Hz (this allows for faster flying speeds than previously possible), and there are data compression options for 10 bit, 12 bit, as well as the raw data.

The ADS80 also features a new design for the Control Unit (called CU80). The new Control Unit is smaller and contains an integrated slow for two Mass Memory units. Here what the new CU80 looks like:

The new system also introduces a new solid state Mass Memory unit (MM80). This size is smaller and weights only 2.5 kg, and has a few different options for data storage modes: single volume, joined volume, and in-flight backup. The joined volume of the two MM offers the greatest data throughput as well as the largest storage capacity, which is ideal for large-area collection missions.

For direct georeferencing applications, IPAS comes embedded in the control unit as well. This is critical for image collection missions in remote areas where ground control may not be possible: this is important in applications such as disaster mapping, remote area mapping (e.g. certain pipeline mapping applications) as well as surveillance operations.

Overall, the system weight has been reduced by 26 kg! It also contains new periphery equipment, including a new GPS/GLONASS Antenna.

Lastly, what does the imagery look like? In short, it looks fantastic. Here’s a sample of imagery collected at 5cm GSD over Lucern, Switzerland earlier this year (click on the image for a larger view).
More information, including both a product brochure and data sheet, is available from the Leica Geosystems website. Also note that new a new software package for ground processing, called XPro, will also be released quite soon.

Special thanks to Ruediger Wagner, ADS Product Manager at Leica Geosystems, for providing details on the new sensor.

Sensor Spotlight: Thailand Earth Observation System (THEOS)

You might have noticed that last year we released a PR regarding support for the THEOS sensor model in both LPS and ERDAS IMAGINE, which was due to launch last week. Unfortunately the satellite launch has been postponed, but we're looking forward to a successful launch once the new date has been set.

A THEOS engineer, Suwan Vongvivatanakij, put together an excellent overview presentation for the CEOS Working Group on Information Systems and Services (WGISS) for their meeting last February. I haven't seen a lot of detailed information about the satellite on the web and thus far this is the most comprehensive info I've seen.

The satellite has panchromatic and multispectral modes, with a 2 meter resolution at nadir for panchromatic and 15 meters for the multispectral mode. For mapping, stereo applications will be supported since there are three (forward, nadir, reverse) look angles.

If you hail from Thailand (or can read Thai) you can see the THEOS program homepage here: http://theos.gistda.or.th/home.html

Sensor Spotlight: WorldView-1

WorldView-1 is a satellite sensor that was launched in September 2007. Built for DigitalGlobe by another Colorado-based company called Ball Aerospace & Technologies Corp, the satellite is in orbit at an altitude of 496 kilometers. There's a great gallery of the construction of the satellite here.

There is a specification sheet on the DG website that highlights the features and benefits of the sensor. WorldView-1 is a panchromatic sensor that features a 0.5 meters GSD at nadir and 0.59 meters at 25 degrees off-nadir. This makes it one of the highest resolution commercial remote sensing satellites on the market today. See a gallery of imagery here.

Imagery can be purchased at various levels of processing. These include:

Basic: the imagery is provided with a camera model and radiometric/internal geometry distortions are removed.
Standard: georeferenced imagery (but not orthorectified).
Orthorectified: 0.5 meter panchromatic orthos.
Basic Stereo Pair: the imagery has orientation information that allows for 3D content generation in a photogrammetric system.

These products give consumers a lot of freedom in determining the best solution for them. For example, if you want complete control over all the photogrammetric processing, then the Basic product will be the best choice. For GIS users that want an imagery backdrop for their application, the orthorectified product is a good option. For users that don't have any ground control (for triangulation) but still want to extract 3D information in a photogrammetric system, the Basic Stereo Pair is a good solution. This option is also good for remote areas where collecting ground control is difficult, expensive or dangerous.

We added support for WorldView-1 data in the LPS 9.2 release, which will support all the products mentioned above. Specifically, you could use LPS to triangulate the imagery, adjust the radiometry, extract and edit terrain, extract 3D features, create orthophotos, and create final image mosaics.

Lastly, for more information on satellite photogrammetry check out this article in the Earth Imaging Journal. It is written with IKONOS imagery as the example but is applicable for Worldview-1 data processing as well.

Sensor Spotlight: the RC30

Since I covered a satellite sensor in the last sensor spotlight, I thought I would go for a airborne sensor this time. The focus of today's post is the RC30, which has been the workhorse of the airborne mapping community for many years. Introduced in 1992 by Leica Geosystems, over 400 cameras have been deployed all over the world.

About the sensor: the RC30 is a frame camera system that can capture imagery in color, panchromatic, and false color film. There are a couple of different lens options (6 and 12 inch focal lengths), which allow for large-scale mapping applications. Complete specifications are available here.

For an example of what RC30 imagery looks like, check out the orthophotos available online at MassGIS. These were flown by Keystone Aerial Surveys, who also happen to have a great photo of the camera on their site here. Other components in the system may include a GPS/IMU system, a PAV30 gyro-stabilized mount, a GPS reference station, and more.

In LPS, the workflow for the RC30 is the classical frame photogrammetry workflow - it is basically the workflow outlined here.

Lastly, just to demonstrate the longevity of this sytem, check out this advertisement from 1988 for an RC20 (Wild Heerbrugg was an earlier incarnation of Leica Geosystems). The RC20 was the predecessor to the RC30, and is essentially the same except for the addition of gyro-stabilized suspension on the RC30. Aside from that, I just think it is a very cool ad!!!

Sensor Spotlight: ALOS Prism

While there is a lot of interest in "high resolution satellite/airborne data" out there in the blogosphere, I haven't seen much discussion on the merits of individual sensors. Hence, I thought it would be interesting to focus a post now and then on individual satellite and airborne sensors.

One satellite sensor that has been getting a lot of attention lately is ALOS PRISM (Panchromatic Remote-sensing Instrument for Stereo Mapping). ALOS was launched on January 24th, 2006 from the Tanegashima Space Center in Japan. While the focus of this post is on the PRISM sensor, the satellite also hosts two other on-board sensors: the AVNIR-2 and PALSAR sensors.

The unique aspect of the PRISM sensor is that it has it is a pushbroom sensor, with three optical systems for capturing forward, nadir, and backward imagery. At nadir the spatial resolution is 2.5 meters. The complete specs are here. For stereo photogrammetry applications, the key factoid about PRISM is that it collects stereo imagery, so it is possible to extract 3D terrain and feature information.

RESTEC, the Remote Sensing Technology Center of Japan, also has a wealth of information on ALOS and ALOS PRISM. In addition to all the background information, it also has some useful sample data. Here is a sample PRISM image. RESTEC has also developed an ALOS Viewer application that can be used to open images from the various ALOS sensors and perform basic operations like measuring distance and, in the case of stereo PRISM data, manually measuring building height.

Lastly, one thing to note is the the ALOS PRISM rigorous sensor model is supported in LPS 9.2. If this is a data type you need, please look into getting your hands on the new version!