# Optimization of Control Point Layout for Orthophoto Generation of Indoor Murals

## TL;DR

This study finds that using 24 control points per 16 square meters optimizes the accuracy of digital images of indoor murals for preservation.

## Contribution

Proposes an optimal control point layout for high-precision orthophoto generation of indoor murals.

## Key findings

- Image accuracy improves with more control points but stabilizes at 24 points.
- 24 control points per 16 square meters meet millimeter-level precision requirements.
- The layout reduces time costs while ensuring reliable data for mural preservation.

## Abstract

This study focuses on the preservation of indoor murals, which can be supported by combining RTK and total station technology to explore the optimization of image geometric accuracy based on a control points layout. The study involves placing varying numbers of control points on the mural surface and processing the collected data using a spatial coordinate transformation model to assess the impact of different layouts on image accuracy. Some control points are used to ensure the spatial positioning accuracy of the images, while others serve as check points to validate the geometric precision of the images. After data processing, high-precision digital orthophotos are generated using Agisoft PhotoScan2.0.1 software, with accuracy verified by the check points. The experimental results show that as the number of control points increases, image accuracy improves gradually. When the number of control points reaches 24, the geometric accuracy of the images stabilizes, and further increases in the number of control points have a limited effect on improving accuracy. Therefore, the study proposes an optimal layout scheme: 24 control points for every 16 square meters. This scheme not only meets millimeter-level precision requirements but also effectively optimizes resource allocation and reduces time costs. The research provides reliable data support for the high-precision preservation and restoration of murals and offers important references for similar cultural heritage preservation projects.