Whenever people talk about drones or drone mapping, the term ‘orthomosaic map’ always comes up. This is because it is one of the most vital deliverables for professionals who deal with drone mapping. But the question is what is an orthomosaic map and how is it developed? What industries rely on these maps?
An orthomosaic map is a presentation that’s free from distortion of a place that is factual to geography and used to get accurate measurements between points. The maps are used for different purposes in different industries or sectors. For example, they can be used in the real estate industry, agriculture, drone photography, law enforcement environmental conservation, and construction. To be able to create an orthomosaic image, a number of 2D images are “sewn” together to form a composite image by the use of overlapping sections of images as points of reference.
Later on, distortions caused by external factors such as topographic relief, camera tilt, and lens distortion are corrected using a process known as orthorectification. This is meant to make the final map a perfect representation of the real world.
What are the common issues of orthomosaic images?
UAV technology has made the making of digital maps much simpler than it used to be. All you need to do is to set up a flight path then collect and process images. Nonetheless, without a proper plan and execution strategy, it can be a hassle to get a perfect end product. Below are some of the challenges that you are likely to face when making orthomosaic images:
- Low detail – out-of-focus or low-quality cameras, poor lighting, or bad weather conditions can lead to vignetting, blurry or unclear images plus other distortions.
- Not adequate overlap – Lack of a proper overlap between the processing software and images won’t produce a full map. This can lead to inaccuracies, distortion, and a lot of gaps.
- Irrelevant images – Images taken from a non-consistent angle will likely bring out ambiguities in the map.
How do you capture high-quality images for orthomosaic purposes?
The secret to a perfect or high-quality map begins with a properly executed flight. The following are some tips that will help you capture perfect images for your maps.
1. Speed and altitude
It is important to note that lower altitudes make it easy to capture detailed images. This means that your final map will have a lot of information about the area you are targeting.
Nonetheless, a low altitude together with high speed can produce blurry images that will make it hard for the processing software to stitch.
Altitude should be set above the targeted object and should be changed during the flight based on the terrain of the area such as the height of the building and other features in the landscape.
2. Image angles
Orthomosaic images should be taken at the nadir. This means that your camera should be pointed downwards. Besides, the interest’s field of view should be perpendicular to the ground or object on the ground level.
If you happen to take a non-nadir image instead or a nadir one, there will be distortion on the final map – hence reducing the level of accuracy. Non-nadir images should only be captured to accompany nadir images in order to offer a more accurate composite.
3. Image overlap
You should always ensure that you prepare for at least 70 percent image overlap. However, you should consider the amount of detail needed for your project. Some projects will require 90%, others 70% while some can get as low as 60%.
What you need to understand is that the more overlap between images, the more points of data processing a software will have to generate the composite map. Note that a lot of images can delay processing time.
4. Lighting and camera settings
Before starting your project, ensure that you have checked the settings of your camera to have the best configuration. You should specifically check on the brightness as well as quality contrasts. Lastly don’t forget to control things such as weather, time of the year, time of the day – because they affect the quality of lighting.
What to consider when purchasing the best software for digital maps
There are a number of software in the market that can be used to convert raw data into orthomosaic images. The following are some of the things you should consider when choosing one:
Even with the best images at your disposal, creating high-quality maps to a large extent depends on the type of processing software being used. Get software that has accuracy tools such as scale constraints and ground control points (GCPs).
Some drones have software mapping software platforms that operate from the cloud while others run on-premises. The latter is slower compared to the former. That’s why it is recommended to use platforms that run on cloud-based technology.
The last thing you can expect is to experience a crash or error while creating large maps. It’s also wise to choose a drone photography software that is easy to learn and use.
If you are in the process of learning about orthomosaic maps, or need one done for your business, reach out to us and we can help you with all your drone mapping inquiries. Contact us today to get a free quote.