Wednesday, February 25, 2009

FugroViewer: Viewing 3D Data

As announced in their newsletter, Fugro EarthData has released a 3D point cloud viewer called the FugroViewer. This appears to be the latest in an assortment of freeware LIDAR/point cloud viewers on the market. In The Scan has some interesting commentary on these here (and there is also the LPViewer from QCoherent in addition to the ones listed).

Lately I've been taking a look at the various viewers, as we have an R&D effort focusing on 3D terrain in the ERDAS photogrammetry group. It is exciting technology to work on and we're very much looking forward to getting it out our of the lab and into our commercial software later this year.

After giving the FugroViewer a whirl it became immediately clear what the competitive advantage is: it is blazing fast in terms of the point rendering, refresh, and tinning. I was working with LAS datasets between two and twelve million points and both the load time and performance (on my laptop) were great.

Here's what a LAS file looks like loaded in FugroViewer. The initial view when you load a file is from a top-down perspective.

The user interface is fairly intuitive, and there are options for viewing the file in 3D, drawing/visualizing a user-defined profile, and numerous options for display (e.g. point coloring, TIN display, contour display, etc.). When you press the 3D button a new display panel opens on the right and a navigable 3D view is rendered, displayed below.

Here I have drawn a profile in another scene: you can see the profile overview in the left panel and and the profile view on the top right display. In this case the profile starts on the bank of a river and moves up a hill, with a church on the right hand side (which can be seen clearly if you click on the image to take a look at the larger view).

The software also displays file information about the LAS file - point count, points by return, LAS version, and so forth.

Overall I'd recommend giving it a try out if you're a regular using of LIDAR data, the performance is excellent and you can't beat the price.

Monday, February 23, 2009

OGC Standards Working Group: IGS-IGM

A major challenge in the world of photogrammetry is data interoperability. I touched on this last week when discussing stereo imagery as a data product, in the context that a practical standard for photogrammetric metadata is inhibiting the adoption of stereo imagery as a data product.

Fortunately efforts are underway at the OGC to resolve the issue. A standards working group for Image Georeferencing Service and Image Georeferencing Metadata was formed late last year to shephard these two draft standards through the standards adoption process. Early drafts were initially submitted in 2006 and have been evolving since then.

At a high level, the Image Georeferencing Service (IGS) refers to a service interface standard for georeferencing (triangulation). Image Georeferencing Metadata (IGM) is a set of schemas that define geopositioning metadata. In the context of a client/server application the input would be non-georeferenced imagery. The service would consume the initial IGM (initial metadata such as sensor name, image names, etc), triangulate the imagery (e.g. provide server-side georeferencing) and then return updated IGM results. In my opinion it makes a lot of sense to develop these two standards instead of implementing proprietary solutions, both for the sake of the mapping community and also for vendors and other organizations that deal with photogrammetric metadata.

Both ERDAS and BAE are participating in the standards working group and we are interested in getting greater participation from the geospatial/photogrammetry community. If you would like to participate, please don't hesitate to get in touch with myself or Dr. Stewart Walker, the IGS-IGM SWG Chair. Also please note that you need to be an OGC member or an employee of a member organization to participate in the SWG.

Tuesday, February 17, 2009

3D Ski Slopes

In my last post I briefly mentioned photogrammetry-oriented web-services delivering data products that essentially hide the photogrammetric aspect of the data processing. But how about pre-packaged fused geospatial data products such as the 3D maps?

After seeing the post on these at All Things Digital, I checked out the site and was duly impressed. The ski maps fuse 3D terrain, vector data, and topo maps and package them up in a nice java-based viewer. There isn't any coordinate display but as a visualization tool the maps are excellent.

I suppose pre-packaged products are the distant cousin of web services. They aren't as sophisticated or flexible and the level of interactivity is limited (for example, you cannot interactively turn layers on and off in the ski maps), but they are dead-easy to use. It isn't an apples-to-apples comparison, but a lot of pre-packaged products seem easier to use than some of the services-oriented GIS web mapping implementations I've seen (although I won't pick on any in particular). Or the other way around, I think that presentation and usability need more attention in many geospatial web-mapping implementations.

Monday, February 16, 2009

Stereo Imagery as a Data Product

Considering the number of geospatial data products that can be derived from stereo imagery, it can seem surprising stereo images are not a widespread data product in their own right. Currently the main vendors of stereo data products are satellite operators such as DigitalGlobe (see here for their basic stereo pair product). Data derived from stereo imagery includes terrain, 3D vector data, and digital orthophotos: three of the most common products in the industry. Also consider that there are plenty of software packages on the market for creating orthophotos, generating and editing terrain, as well as working with vector data.

So why is it rare for stereo imagery to be sold as a "product"?

Personally I think there are a few reasons for this. These include:

  • There's no practical standard for storing photogrammetry metadata (e.g. image exterior orientation parameters). Although there are efforts underway, photogrammetric metadata is typically stored in proprietary formats. This inhibits the ability of the data to move from system-to-system. For example, if the imagery was triangulated in System X and then provided to a person using System Y, they invariably have to go through some pain and suffering to ingest the data (running an import job at a minimum).
  • Airborne flight operations are expensive. Data providers are typically contracted to fly specific jobs for clients such as regional authorities and so forth (here is an example). Times may be changing, but I haven't seen too many companies out there flying stock imagery and then reselling it. This is partly tied to the point above - without a common system for storing photogrammetric metadata, it is difficult for data vendors to deliver a one-size-fits-all solution.
  • The workflow is perceived as being difficult. For example, you need specialized and expensive stereo viewing hardware, domain knowledge in photogrammetry, etc. It all depends on the application, but if you're not performing stereo work all day long as your primary job, then it is still possible to get high-accuracy results working in split-screen or anaglyph mode. As for the domain knowledge, once the imagery is triangulated, then derived products such as the ones above are very easy to create - although they can be time-consuming depending on the project size.
It will be interesting to see if stereo imagery develops as a data product or if there will be a migration to photogrammetry-oriented web-services that essentially hides the process from users. For example, perform server-side orthorectification with a catalogued RPC image and terrain model and then deliver the orthorectified image as a WMS or WCS. This kind of functionality is on the market now, and I think it could be poised for growth...

Wednesday, February 11, 2009

Innovative Applications in Photogrammetry

If you have been to the ERDAS home page lately you may have seen the "Top 10 Reasons to use..." lists for IMAGINE and LPS. While thinking about the "Top 10 reasons to use LPS", I also researched innovative uses of LPS and photogrammetry in general. I have listed some of the most interesting applications that I have come across below. Note that the list below is LPS-centric, although many of these applications used a mix of tools. I believe the list illustrates how useful and flexible photogrammetry is as a tool for any 3D geoinformation research.

So here is an alternate list outlining 10 innovative photogrammetric applications (in no particular order):

  • Studying Medieval Architecture. LPS was used to generate and analyze 3D models from stereo imagery to examine the metrology and proportional systems used in the design of Irish ecclesiastical architecture.
  • Mapping Landslide Debris. LPS was used to rectify ortho-images and extract terrain in a study based on a 1999 earthquake in China.

Thursday, February 5, 2009

ERDAS Image Web Server Demo Site

With the days of authoring geospatial image products and then shipping them off to customers on DVDs coming to a close, I would like to highlight a demo website for the ERDAS Image Web Server. IWS is a solution for serving imagery to web clients, geospatial applications, or mobile devices. Here's what a snippet of the "Home" section of the site looks like:

The interesting parts of the demo site are in the "IWS in Action" drop down menu. The options provide examples of what is possible with IWS. Some examples include:

  • Geo-linking Images
  • Geoprocessing
  • GIS Integration
  • Image Enhancements
  • Massive Terabyte-Size Imagery
  • Real-Time Tracking
  • Reprojection
  • Time Series Data
  • World Image Gallery
  • and samples packaged with IWS
If you're been checking out the new capability for viewing historical imagery in Google Earth 5.0, then check out the "Time Series Data" example - this demonstrates how your own historical or time-series imagery could be served up. Personally I think this is a big potential growth area, as it allows viewers to quickly assess change over time in a specific area of interest. There is a massive amount of historical ortho imagery out there, so it is great to see organizations starting to put together applications for enabling visual change detection.

The World Image Gallery also has a large amount of example datasets. This is worth a look because it displays the performance of datasets of various type and size. Here's a screen shot of a San Diego area mosaic:

The Geoprocessing section shows off some interesting options as well. The example below shows the hillshading capability.

Hopefully you find the site useful, and please feel free to send us feedback or suggestions.

Wednesday, February 4, 2009

Europeana: Historical Maps Online

I was browsing around Europeana, which made international news with its debut and subsequent crash in November, when I found that it is a great resource for archived historical maps. If you visit the site and search for, say, "map", you'll get all sorts of results. The "refine your search" tools on the left are good for filtering by country, provider, or other parameters. For instance, I filtered on Bibliotheque Nationale de France as the provider and found a great historical map of the British colonies in the USA and southwestern Ontario. Clicking on the "view in original context" will take you directly to the source, which in this case takes you to a full-screen viewing application when you double-click on the map.

The British Library, another "provider" search refinement option, has an impressive number of historical maps as well. They are also available in a nice flash viewer, such as this 1530 map of Ireland.

Monday, February 2, 2009

Oblique Imagery

From my perspective the market for oblique aerial photography has gone from a very niche application area and morphed into something altogether different. With the advent of organizations like Pictometry and applications of their photography such as the "Bird's Eye" view in Microsoft Virtual Earth, oblique imagery is entering a number of market spaces. Oblique aerial photography is not new though, however early attempts to commercialize the technology such as Kodak Citypix from several years back never really got off the ground.

I would be interested in thoughts on usage of oblique photography versus nadir "top-down" orthophotos. My view is that nadir photography is most appropriate for "measuring" objects within photos (GIS "backdrops", building areas, parcels, roads, etcetera), whereas oblique imagery is better for contextual information. So from a "mapping" perspective traditional top-down imagery may be more appropriate but for a navigation system my preference would be for oblique.

From an end-user/consumer perspective there is certainly a lot of value in oblique photography. One problem with nadir imagery is that it can be difficult to tell how tall buildings are, or gather any information about buildings (or anything other features with a "vertical" aspect). Oblique photography allows users to see the sides of buildings and other objects, which has a lot of appeal for a variety of applications.

The downside of oblique imagery is that, depending on the angle, objects in the foreground (e.g. highrises) can obstruct the view of anything behind them. They can also be difficult to integrate in a GIS, as most GIS apps feature a "top-down" perspective when you're looking at the data. For photogrammetric applications, it also isn't very practical to work with high oblique images in stereo.

Here's an exampe: the image below is a nadir view from Microsoft's Live Search Maps in Pacific Beach, San Diego. One can clearly see roads, all the buildings (from a top-down perspective), and the coast.

The image below is the same area with the "Bird's Eye" oblique perspective view. It immediately becomes apparent that there is a highrise along the coast, which obstructs the view and casts a shadow on several buildings behind it - useful to know if you're in the real-estate business. The bluffs along the ocean are also exposed.

And finally, here is another oblique aerial photo of the same area taken facing east. This is a closer-range and lower-altitude oblique shot than the images above, so a lot of building detail can be seen (e.g. one can determine the number of stories of the properties along the coast). This image also illustrates how the objects behind the highrise are obstructed - you'd need to take a look at the "top-down" nadir view to know what is there.

Click on the thumbnail above for higher resolution

Incidentally, the above photo is from the California Coastline Records Project. If you haven't heard of it, a visit to the site is highly recommended. The project has coastal oblique coverage of nearly the entire California coastline, taken from a helicopter approximately 500 feet offshore. The project has essentially created an online repository documenting the status (and damage to) the coastline. In celebrity news, the project was unsuccessfully sued by Barbara Streisand, who took issue with online photographs of her Malibu compound...