Title: Lesson 4: Orthophoto generation
Course: Photogrammetry applied to drone image acquisition > Section: Course Content

The last step in the photogrammetry workflow is orthophoto generation. Orthophotos are geometrically corrected images that can be used to generate topographic maps. This lesson will explain what an orthophoto is, the process of orthorectification, and how to assess their quality.

Introduction to the lesson:

The last step in the photogrammetry workflow is orthophoto generation. Orthophotos are geometrically corrected images that can be used to generate topographic maps. This lesson will explain what an orthophoto is, the process of orthorectification, and how to assess their quality.

Objectives:

The main objectives are:

- To define the concepts: orthophoto, orthorectification, Digital Surface Model, and Digital Terrain model;
- To describe geometric and radiometric image distortions and how these relate to orthorectification;
- To apply the learned orthophoto generation procedures using the designated commercial software (Pix4D) for drone images.
- To quantitively and qualitatively assess the quality of orthophotos and describe possible causes;

Entrance requirements:

Followed the previous lesson of this course and conducted the exercises.

Learning activities:

- Study the lesson document (EENSAT_PD_L4_Orthophoto_SlidesHandout.pdf), and watch the designated links if described in the document
- Review the background literature (pages 39 – 52 of the Community Urban Risk Mapping Cookbook).
- Prepare exercises as described under “Tasks”

Tasks:

The task for this lesson is to conduct Practical lesson 4 (Chapter 3.4): DSM and Orthomosaic. This task will guide you how to generate a DSM and Orthomosaic in Pix4Dmapper. Submit the answers to the questions in the “Delivery” part of the lesson to the EENSAT Education Portal.

Planned time frame for this lesson:

7 hours