OSi are upgrading their aerial tech to bring you Ireland in high-resolution
With the installation of new aerial cameras in OSi’s aircraft this week, we are about to radically improve the way aerial imagery is captured and processed in Ireland.
Here at Ordnance Survey Ireland (OSi), we’ve been photographing the Irish landscape from above since the 1970s. Originally, the imagery was captured by the Air Corps, but from the early eighties we’ve leased two planes (Piper Aztec light aircraft) and operated our own image-capturing flight missions from Shannon airport.
State-of-the-art aerial technology
Our existing aerial technology is made by Leica Geosystems, a camera manufacturer renowned for image quality, accuracy and processing speed. This week, we are replacing our existing technology, with Leica’s latest, state-of-the-art ADS100 cameras.
New tech versus old tech
With our existing equipment, we were using two different technologies to photograph the landscape:
- Digital frame technology: In one plane, we were using what’s known as a ‘digital frame’ camera. It captured thousands of individual images (frames) as it flew over the flight path. Stitching each one of these individual frames together was a very time-consuming process.
- Push-broom technology: In the other plane, we were using ‘push-broom technology’, which is a sensor that scans a long stretch of the landscape (sometimes up to 50km long) and produces a single long image. It takes much less time to stitch these longer images together.
Going forward, we will use the latest push-broom technology in both planes so that the post-processing of the imagery is faster.
Greater data capture
The new camera can operate at higher speeds and scan a wider area as it passes over, meaning that we can now capture more data per flight.
The new ADS100 has a wider ‘swath’, which means it can scan a wider area of the landscape. The existing push-broom sensor that we had could only scan 12,000 pixels at a time, whereas the new ADS100 can scan 20,000 pixels at a time. What does this mean? It means that a particular land area, for example in Sligo, which originally required 18 flight lines to capture, can now be scanned with just 13 flight lines (illustrated in the images below).
Resolution refers to how much detail an image can hold. With the existing cameras, we captured imagery at a resolution of 1 metre (one pixel on the image equals 1 metre on the ground), but demand is rapidly increasing for a higher resolution 25cm product (each pixel shows 25cm of ground). We were able to produce a limited volume of 25cm product with the existing cameras, but in order to capture it, we needed to fly at a lower altitude.
Upgrading to the ADS100 cameras allows us to capture 25cm resolution imagery at a higher altitude, therefore enabling us to cover more ground per flight.
One of the products we produce from our aerial imagery is what’s known as ‘orthorectified’ photography. Objects can appear displaced in an image because of the tilt of the camera or because of changes in elevation. Orthorectification is the process of ‘correcting’ an image to remove displacement.
The most exciting thing about our technology upgrade is that we can now produce 25cm resolution orthorectified photography for the entire country.
Imagery can be delivered to clients at a faster rate
Once the images are captured, the edge of each flight line (known as a seam line) needs to be joined together. The thousands of small images produced by the existing cameras took a long time to stitch together. The new camera produces fewer, larger images, so the post-processing stage is relatively faster.
For example, to capture the entire country at 25cm resolution, we divide the country into 37 ‘blocks’. When we used the existing digital frame camera to capture one particular block, we would end up with approximately 1100 seam lines to process afterwards. Now, when we use the new camera to capture that same block, we will only have approximately 30 seam lines to process.
A shorter, more efficient post-processing stage means that we can deliver data through to our clients at a faster rate.
Updated on a 3 year cycle
Since the mid nineties we’ve been able to release a 1m resolution orthorectified product for the entire country every 5 years. We also released a limited volume of 25cm resolution product for some large towns and cities.
We no longer produce the 1m product and instead have embarked upon a new nationwide 25cm resolution product. With the new technology, we will be able to release this national product every 3 years.
Opportunity to capture advanced data
‘Point cloud’ is a term that relates to generating 3D representations of the landscape. Our new cameras have advanced capabilities in generating point clouds. This is great news for OSi because 3D data capture is next on the horizon for us.
The new camera also has advanced infrared capture abilities, which will provide opportunities to potentially develop new products, for example vegetation analysis.
Who uses OSi’s aerial photography?
OSi are mandated by the state to capture and supply aerial photography for its users. Our imagery is often used by County Councils for planning purposes, for example to plan new housing estates. The Department of Agriculture sometimes uses our imagery to determine what area of a farmer’s pasture qualifies for EU grants. Our imagery is also used to monitor changes in the landscape, such as coastal erosion, or to evaluate illegal landfill and dumping sites.
The images below illustrate how a landscape has changed over time due to quarrying. These images would enable an authority to ensure that the land boundaries identified in the quarry’s license are not being breached.
Find out more about obtaining OSi’s aerial photography here.