How do we make maps from Orthophotography?

The art of map making has come a long way, mainly thanks to aerial photography.

Early map preparation was a long and painstaking process. Cartographers set out by foot to literally walk the land and draw as they went.

In the 1940’s as technologies evolved, cartographers began to use 5 lens cameras and instruments called stereoplotters to make the art of map making easier.

Fast forward to today, quality maps are now made using an airplane and digital cameras. This brings us to aerial photography and the advent of orthophotography.

What is orthophotography?

An orthophotograph, orthophoto or orthoimage is an aerial photograph which has been orthorectified. Orthorectification removes any distortions in the image which are caused by camara angle and topography to produce a scale-accurate image.  Tailte Éireann - Surveying regularly make flights to capture aerial images.

How is an orthophoto different to a regular photo?

If you view a landscape image in the scale of a regular photo, the objects in the photo won’t be uniform. Objects at the edges or in the foreground will have a different scale to objects in the centre or background.

Does this really matter?

If you are just looking at a beautiful landscape, city scape or family portrait, probably not. But if you are trying to make meaningful planning decisions in the area pictured, you will need a true reflection of the area and its dimensions.

A wide range of conditions can distort the scale in a regular photograph, such as topography of the area, lens distortion, camera movement and camera tilt.

How is this rectified?

Once the images are collated they are orthorectified using a Digital Terrain Model which is generated from our aerial imagery

By using this data to correct heights, depth and any other contours which occur in the image, orthophotos give the most accurate depiction of the area.

Orthophotography is now the basis for map making and gives us a true perspective on how buildings, trees, valleys and bends in a road truly appear in an area.

Why would you use an orthophoto?

Orthophotos can be used to create spatial data. Aerial imagery, ortho and geographic spatial data can be integrated in a GIS (Geographic Information System).

GIS is the integration of the physical imagery with the geographic data.

By layering the information, it is possible to create different types of map from a simple road map to a scrollable 3D visual of an area. Software programmes can be used to add lines, symbols, annotations and other markers to help process the image.

Do we need this much information?

Of course. Using GIS means we can learn more about an area and therefore make better decisions. This can save businesses lots of time and money.

Who uses orthophotographic imagery?

Here are some examples of industries that would use orthophotographic imagery and their application of this.

Insurance Location and the topography can impact the risk assessment when purchasing an insurance policy and therefore influence insurance quotes and claims.

Public Safety Having an accurate map of an area enables communities to respond appropriately to emergency situations and reduce response times. It also helps organisers better plot incident histories, identify vulnerable areas and plan for any future problems.

Transportation It goes without saying that a high-quality map of an area and its infrastructure is crucial for transportation planning, monitoring and strategic management going forward.

Property Property companies have a better chance of spotting development opportunities if they have a detailed understanding of an area. A GIS provides the best location-based data to help understand trends that are impacting an area.

Telecommunications Whether the company is fixed line or mobile, advanced mapping analytics can ensure the company is maximizing its return on network investments in an area.

Retail A GIS overlaid with demographic information would allow retailers to forecast potential customer numbers, supply chain routes, profitability and more.

You can find out more about Tailte Éireann - Surveying mapping services here.

If you have any questions about how our professional mapping services can help you make better strategic decisions, don’t hesitate to contact our team at mapsales@tailte.ie