Drones and 3D City Modeling

Urban planning is important in the administration of any city. It helps optimize the city’s infrastructure for service delivery to inhabitants. It also helps visualize planned changes, which helps assess their impact and effectiveness, in addition to greatly simplifying communication at the conceptual stage. 

The benefits above are just some of the numerous reasons why governments develop 3D models of their cities. 

The utility of 3D city models is clear and now the question becomes: What’s the best way to go about 3D city modeling? 

Aerial systems immediately come to mind. Thanks to aerial imaging systems, developing a 3D model can be as easy as flying over a city. 

Apart from ease, another important consideration to make is the quality of the model. The quality will be determined by the techniques and software you use. But the quality of the sensors you use to collect aerial data will be an even more important factor. 

This article will explore the use of drones and the drone camera in the generation of 3D city models.

How 3D Models Are Created Using Photogrammetry

Aerial systems can take photos from the air. To do that, you just attach a payload to an aerial vehicle such as a drone or helicopter. You can even do it with a plane if you are covering huge distances. 

But a 3D model is a far cry from a simple photograph. A 3D model can be 3D printed to come up with a realistic object with length, width, and depth. A photograph can only be viewed on a screen or printed on a paper-like medium. 

How do you get from 2D photographs to 3D models? Using photogrammetry. 

In photogrammetry, you take multiple overlapping photos of the area of interest. You then stitch them together using specialized software to come up with three-dimensional data. 

Additionally, especially in the creation of 3D city models, you need to capture GIS data and ensure that each point on the model is associated with an actual point on the ground. That way, you get an accurate representation of the city. 

The Use of Drones to Create Aerial 3D Models 

If the area you want to model is extensive, for example the entirety of a large city, you might be better off using a high-quality sensor payload attached to a plane. It is possible to use an aerial mapping system that enables all the necessary data to be captured in one flight, with multiple, high-resolution sensors; as high as 100 MP. 

However, in some situations, you might prefer to use a drone attached with a drone camera. This is so especially when mapping a small area, for example a certain sector within a city. The use of drones is also more cost effective. 

When using a drone to create a 3D model, you’ll typically need to make a few passes over the area. At the very least, you’ll need to make two passes, one to capture nadir imagery and the other for oblique imagery. 

Combining the two types of imagery results in better 3D models. 

Overlap is also important in the quality of 3D models. The higher the overlap percentage, the better the resulting 3D model. 

Here are a few more considerations when recording data: 

• Speed. The speed of flight of the drone should account for the rate of image capture. The speed should be set to allow optimal overlap. 
• Altitude. The height of flight should be such that you can avoid tall buildings. 
• Distance between transects. 
• Internal geometry of the drone. 

The type of drone and payload you use will greatly affect the quality of your data and the ease with which you can collect it. 

Potential Uses of 3D City Models 

3D city models can be used for a range of specific applications. 

Land Use Analysis

The use of land in a city can be effectively analyzed from a 3D city model. This can help analyze the success of city planning efforts and make further plans for the future. 

Land use can be divided into commercial, residential, transport, open space e.t.c 

Population Estimation

From a 3D city model, the total volume of buildings can be determined and used to estimate the number of people that live in the city. 

Street Pattern Analysis 

3D city models can be used for street analysis. Apart from helping distinguish between the types of street patterns, they can help determine the causes of the difference in patterns. 

Building Pattern Analysis 

For anthropological and architectural purposes, the patterns of buildings in a city can be analyzed using a 3D city model. Different types of buildings can be identified, with the different types being classified.