Overview
It's important when it comes to photogrammetry and 3D Modelling that you understand what the terms and abbreviations are and what they are used for.
In this post, we will be looking at two very common terms and why using them together is very important to create the best 3D Model possible.
The terms we will be looking at are 1) Nadir and 2) Oblique Images.
1. Nadir Images
The nadir is the direction pointing directly below a particular location; that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface.
In simple terms, a top-down view of an object or structure.
Below is an example of a nadir shot:
Oblique
An Oblique can best be described as neither parallel nor at right angles to a specified or implied line or at a slanting angle.
Pic Credit: Advanced Geographic Research
In the case of photogrammetry, the obliques are taken around the sides of the building at an angle to help determine the facades or sides of the building or structure.
Below is an example of an oblique shot:
So Why Do Obliques Matter?
Obliques help to create a more complete 3D Model through the use of photogrammetry. Adding the sides or facades by using oblique capture adds more detail and more data to your model.
Photogrammetry is the science of making measurements from photographs. It involves using specialized software to extract measurements and 3D information from 2D images. This technology is used in a variety of applications, including surveying, mapping, construction, and industrial design.
The process of photogrammetry involves taking photographs of an object or area from multiple angles. These images are then analyzed and processed using photogrammetry software, in our case Hammer Missions, which uses algorithms to identify common features in the images and create a 3D model. The resulting model can be used to make accurate measurements, create maps and 3D visualizations, and analyze the geometry and dimensions of the object or area.
Photogrammetry is used in a wide range of industries, including engineering, architecture, archaeology, and environmental management. It has become an increasingly important tool in fields such as urban planning, where accurate 3D models of buildings and terrain are essential for creating detailed plans and simulations.
For more information on 3D Modelling please see our previous post:
Examples
So now we have looked at why obliques matter when collecting data for 3D Modeling we can look at some examples of where obliques haven't been used in a 3D model capture compared with where obliques have been used.
Both of these examples were captured using Hammer Missions with a DJI Mavic 2 Pro drone
Without Obliques ❌
You can see from the image above that a lot of the detail is either missing or completely unavailable. The parts of the facade that have been captured have been acquired via the nadir from when the camera has been looking directly down over the facade.
With Obliques ✅
You can immediately see the difference between the two models, the first thing that stands out is the gain in quality. By adding the obliques you can now define the sides of the building, giving it a more 'real' representation.
Layered Missions
To be able to define where exactly your oblique mission must be placed we, Hammer Missions, have created a method of creating layered missions.
A layered mission will allow you to 'layer' missions on top of each other so that you can see where your previous mission sits on the map.
You will see from the example above that our obliques missions (the blue lines around our structure) have been layered on top of the 3D Mapping Mission (in light grey).
This gives the operator the opportunity to know where the existing mission sits so that they can accurately place a new mission, in this case, an oblique mission, over the top.
This is very important when it comes to photogrammetry as it allows both oblique and 3D Mapping to blend.
This is further discussed in the video below:
For more information on how to set up mission layers please see our post below:
Summary
We hope the article helps you understand what oblique images are and why they matter.
If you'd like to learn more about how to capture high-quality data and get the most out of your drone flights using our cloud-based platform, please feel free to visit our learning resources.
If you haven't got a Hammer account and would like to try Hammer Missions you can get started on our free trial.
To learn more about our enterprise solutions, including mission collaboration, data processing, and AI solutions, please contact us at team@hammermissions.com.
We look forward to hearing from you.
— Team at Hammer Missions