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A composite of 380 100MP aerial images has been created of the site of Apple’s new campus by photo mapping and data company SkyIMD. The company usually provides the kit for other aerial photographers to use, but on this occasion wanted to show off the amount of detail that can be captured with a Phase One iXU RS1000 100MP aerial camera. The company used software to create flight paths over the 0.5 square mile construction site and spent just thirty minutes shooting 420 images with the camera attached to a Cessna 172 light aircraft.
When combined to create a single picture of the whole area, the images allow dramatic magnification so that people in the scene can be picked out – even though the plane was flying at 2000ft with a lens just longer than standard for the format.
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The Phase One iXU RS1000 industrial camera uses the same CMOS sensor that is used in the IQ3 100 back for the XF 645-style DSLR body, but in this case it is used in a body with no moving parts. The firm used a Rodenstock 90mm lens with the body and once all 420 images were combined and cropped to the equivalent of 380 images, the file measured 4.76GB. SkyIMD used Photoshop’s Photomerge feature to combine the images, but to maintain manageable amounts of data the company divided the images into batches of over 70 covering specific areas of the site. Once the batches were combined those composites were also combined to create the final image, which you can see on the SkyIMD website.
SkyIMD’s Michael Estigoy has provided some detail about how the image was shot and created.
All of the images were captured using our FAA/EASA/ANAC STC certified Aerial Camera Platform. The platform mounts to the strut of a plane (Cessna) and holds the PhaseOne iXU RS1000 90mm camera in a vertical (nadir) position.
During the pre-flight process, we used a software program called Flight Planner from AeroScientific (http://www.aerosci.info/flightplanner/) to create our flight paths, and calculate the frequency of the intervalometer based on the speed, altitude and desired GSD (ground sample distance).
Using the PhaseOne iX Capture Software, we set the exposure and ISO to obtain the best image balance we could. There was some consideration given to capture as much detail as possible – balancing the exposure between not making the shadows too dark and whites/brights too blown out.
We loaded up the flight plan on our iPad – we use an application called Galileo Offline Maps (https://galileo-app.com/) – to depict the flight lines and line up our airplane. Our pilot, who has years of experience flying missions like this, lined up the plane at the speed and altitude we calculated pre-flight, and then flew the lines straight and level. I controlled the camera operation and made sure that the image quality and coverage was being captured successfully.
The parcel required us to fly 7 flight lines to capture the imagery. We flew one grid.
We are planning follow up flights and will fly a double grid pattern on those, or a cross hatch pattern, to capture more images and enable us to create better mosaics and perhaps a 3D model or flyover.
Stitching and imaging process
We typically use photogrammetry software such as those offered by Pix4D and Agisoft. However, this time I elected to try and use Adobe Photoshop to create the Mosaic. I used the Photomerge function.
We had a total of 420 images. We have a high-powered computer (8 core i7, 64GB RAM, m.2 SSD drives, etc., GeForce GTX video card), but 420 is almost impossible to process all at once. I grouped the images into six separate folders, each representing an area of parcel. Each group shared some images with the other groups in order to facilitate matching. After each group, or chunk, of images was merged, I corrected them for distortion and then merged the groups together. After merging, any major flaws were cut out and images were sourced to fill in the holes.
Photoshop used 90% of our installed RAM and approx. 700 GB of scratch disk space on two m.2 SSD drives to complete each group, including the final mosaic.
As mentioned on our site, we did not take any time to massage the resulting mosaic Photoshop produced. I may have adjusted curves, performed some slight sharpening, and that’s about it. There are obvious mis-alignments and distortions in the image. We wanted to share the image rather than spend another week making it perfect.
The final image was cropped to the final size. I had seen the plans Apple submitted to the City of Cupertino and wanted to try and represent that area of view (pages 3 & 4 of this PDF – https://s3.amazonaws.com/apple-campus2-project/Site_Plan1_Submittal7.pdf). The crop was made visually. We eliminated the use of about 40 photos, hence the approx 380 images mentioned on our site.
The image was too large for TIFF or JPG format so it was saved as a Photoshop Large Document (.PSB). In order to support the zooming feature on our web, we used a photoshop plugin from Microsoft:
http://research.microsoft.com/en-us/um/redmond/groups/ivm/HDView/HDPhotoshopPlugin.htm. This created the thousands of tiles for zooming.
I used Openseadragon for the javascript/web enablement for the zoom/interactive viewer:http://openseadragon.github.io/
Articles: Digital Photography Review (dpreview.com)