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True Ortho aerial photography of Basingstoke, UK

Using XCAM to rapidly collect orthophotos, also, what is an orthophoto?!

We all (hopefully) know by now that XCAM is great for capturing photorealistic 3D models, but orthophotos are still an essential GIS tool.

XCAM is leading the way in the ability to rapidly collect aerial photography to create stunning 3D mesh models. With its unique and efficient circular path survey method we've seen our XCAM clients capture large areas at much lower operational costs than UAV or large format sensors. This has really energised the 'medium format' aerial survey space and is paving the way for 3D mesh models to become 'the new orthophoto'. Ok, a new 3D orthophoto is an oxymoron but we mean the transition from GIS being used in a solely 2D environment to one that is natively 3D.

We'll continue to charge forward in this field but we also have to be realistic. Not every organisation is ready to adopt 3D data or have the flexibility and funds to change GIS software, but they do have tried-and-tested workflows for how they consume and benefit from geospatial data. So at GeoXphere we must provide the technology to fit with those workflows. Our XMAP cloud-based GIS is one solution to this, but that's for another blog article. Here we're talking about the trusty orthophoto.

Firstly, what is an orthophoto?

In the geospatial industry we use the term 'orthophoto' and assume everyone knows what we're talking about, so here's a quick summary:

- Orthophoto

This is the name given to a photographic mosaic of images taken from the air. Another name is 'aerial photography' but this can also be used for single-shot photos. In the survey industry we systematically capture aerial photographs, stitch them together, align them into geographic space (so they line up with other GIS datasets) and deliver them as one big image (or a series of gridded tiles). The resolution (level of detail) of the orthophoto is measured by how much ground each pixel covers. So if it's a 15cm resolution (GSD or Ground Sampled Distance) dataset then each pixel represents a colour for whatever is in that 15cm x 15cm square on the ground. If it's a 5cm GSD dataset then it's representing a 5cm x 5cm square on the ground. Speak to one of our team to help you decide what resolution you need.

Orthophoto from Bing Maps, note the building lean

© Bing Maps

 

- True Orthophoto

Just to complicate matters, there's also a 'true orthophoto' or 'true ortho'. This is exactly the same as the orthophoto described above but with one key difference; buildings and features in a true orthophoto point perfectly vertically which means you can't see the sides of the buildings. This has two benefits; 1) if you draw around the top of the building, the measurement is going to be more accurate than from an orthophoto, and 2) a large building will not 'lean' over and obscure vital information such as adjacent roads and buildings. This gives you a better view of the scene.

Chances are that if you use or procure aerial photography then you'll be getting an orthophoto rather than a true orthophoto. This is mainly because true orthophotos have traditionally been more expensive to capture and process. So even though true orthophotos are a better product, they've been too economically restrictive.

XCAM True-Ortho

 

XCAM for Creating True-Orthos

Now we know what we're talking about let's get back to the issue; even though 3D is the way GIS is going and has many more benefits, 2D GIS still prevails. And actually this is OK. As we mentioned, XCAM is a very efficient way of capturing 3D models, but one of the magical things is that when you put XCAM data into our processing software it also produces a true ortho.... as a byproduct!

The true-ortho that the processing software used to produce a few years ago was good, but not the top-quality that you'd expect from a survey with a large format camera. We're not picking on any one particular processing software here, they all had their issues and it put a lot of people off. The issue was that the software tried to create a true-ortho from the 3D model. If the model wasn't perfect (which none of them truly are) then you would see strange artefacts and wobbly building edges, wonky road lines and strange-looking trees.

XCAM true-ortho data in 2016 
An old true-orthophoto, note the wobbly fence and roof line in the top of the image
XCAM True-ortho in 2017
A current-day true-orthophoto with much sharper roof edges. Also, much higher resolution.

 

 This meant that the customer was having to wait a long time for their data because a) the large format cameras only operate in certain conditions, and b) the processing from medium-format cameras wasn't up to scratch.

That's completely changed now and the processing software capabilities has progressed so far that the true-orthophoto produced with XCAM are class-leading.

 

Ultra-High Resolution True-Ortho

It's not also economically viable to capture ultra-high resolution data over a large area. Check out this dataset of Basingstoke, UK which is a 3.5cm GSD dataset. You can clearly see drainage covers, white lines and street lights.

Ultra High Resolution True-Ortho Aerial Photography by XCAM

 

Best of Both Worlds

So now, whether you're an aerial survey company or a consumer of aerial photography, you get the best of both worlds;

  • Stunning quality thanks to the processing software,
  • A true-orthophoto, not just an orthophoto,
  • Captured rapidly thanks to XCAM's versatility in different weather conditions,
  • Captured cost-effectively thanks to XCAM's ability to survey on light aircraft, and,
  • Delivered rapidly thanks to the scalability of processing software such as Skyline Photomesh.

 

Perfect for now, prepared for the future

This development in technology now allows you to change your attitude on when you can order aerial photography for a project, or how often your aerial photography layer should be updated. You'll be surprised how quickly and cost-effective it now is. You shouldn't find yourself in a situation working (and relying on) data that's over a year old.

And here's the added benefit that ties this all together. If you order data from an aerial survey company that uses XCAM, chances are they'll be able to deliver the true-ortho you asked for as well as a 3D mesh model. If you order a 3D mesh model, you'll also get a true-ortho. This keeps your day-to-day workflow intact but also future-proofs you for using 3D data. There's no downside!

XCAM 3D dataset taken from the same survey used to create the true-ortho images in this article

And the law of unintended consequences says that you're bound to find some benefits from using 3D that you'd never even considered!

 

Check out some of the data that our XCAM customers have captured on our Data Showcase. We're adding data regularly and it's getting better and better. XCAM is operated by many aerial survey companies around the world, including the UK. Check out out Partner page to see if there's one in your area. You'll be surprised how low the quote is!

 


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