Five Tips for Ortho Generation: How to Avoid Failure in Field Drone Photogrammetry

Table of Contents

• Tip 1: Plan your flight meticulously

• Tip 2: Prepare drone equipment and camera settings

• Tip 3: Use ground control points for high-accuracy surveys

• Tip 4: Pay attention to weather, lighting conditions, and safety measures

• Tip 5: Verify captured data on site

• Simple surveying with LRTK

• Frequently Asked Questions

In drone photogrammetry, many photographs taken from above are stitched together to create orthophotos (ortho images) and 3D point-cloud models. However, with even minor preparation lapses or setting mistakes, field work can fail to produce sufficient results. For example, if image overlap is insufficient or focus is soft, processing the data later may yield low-accuracy results and require re-shooting. What should you pay attention to in order to avoid failure in the field? This article explains five tips to reliably succeed at ortho generation in drone photogrammetry.

Tip 1: Plan your flight meticulously

Pre-flight planning is essential to successfully generate ortho images (creating orthophotos) with drone photogrammetry. Before flying, assess the survey area and carefully plan the route and altitude. In particular, photos for ortho images need sufficient overlap between them. If image overlap rates are insufficient, gaps or misalignments can occur during later image stitching, preventing accurate ortho images.

• Ensure overlap of 80% or more: Generally, aim for 80% or more front-to-back overlap and 70% or more side-to-side overlap. Set a flight route that efficiently covers a wide area while ensuring sufficient image overlap.

• Set an appropriate altitude: Choose shooting altitude by balancing desired resolution and flight efficiency. Flying higher covers more area per pass but reduces resolution. Select an altitude appropriate for the detail and intended use of the target area. If terrain is undulating, pay attention to altitude changes.

• Check regulations and obtain flight permission: Confirm in advance whether the planned flight area legally requires drone flight permission, and apply if necessary. If permission is not granted, you cannot fly on-site and the plan will be ruined, so don’t neglect legal checks.

• Plan flight route and battery usage: Include not only the flight route but also battery swap timing in the flight plan. Shooting a wide area may require multiple flights. Decide what to cover in each flight and when to return, to avoid having to abort due to battery depletion.

With careful planning you can proceed smoothly and calmly on site. Also check topographic maps and satellite imagery beforehand to identify obstacles and elevation changes, and plan routes to avoid missing any areas to be photographed. Thorough flight planning ensures you acquire all necessary photos, making subsequent ortho generation far more stable.

Tip 2: Prepare drone equipment and camera settings

Before heading to the site, make sure the drone and camera you will use are in perfect condition. Equipment troubles and setting mistakes are major causes of having to re-shoot even after a flight. Check the following to ensure equipment and shooting settings are prepared.

• Check batteries and storage media: Confirm that the drone and transmitter batteries have sufficient charge and that spare batteries are available. Check the free capacity of recording media such as SD cards in advance to prevent shooting from stopping due to lack of storage.

• Inspect the airframe: Check propellers and motors for abnormalities, and tighten loose screws or replace propellers as needed. Before flight on-site, perform compass calibration and check IMU sensor status to ensure stable flight.

• Camera focus and exposure settings: Set the camera so that infinity focus is correctly achieved. Relying on autofocus can cause focusing hesitation and blur, so if possible fix the lens at infinity with manual focus. Adjust exposure (shutter speed and ISO) to match the weather. In cloudy conditions or shade, shutter speed can become too slow and cause blur; try to use a fast shutter (for example, 1/1000 second or faster) by increasing ISO as needed.

• Keep settings consistent: When shooting across multiple flights, it is desirable that settings are consistent across all images. Fix white balance and use manual exposure rather than semi-auto modes so that extreme brightness differences do not appear across the image set.

Thorough equipment and setting preparation helps prevent failures like “I thought I shot it but I didn’t” or “images are too blurry to use.” Especially in drone aerial photography, once airborne you cannot touch the aircraft, so pre-flight checks are essential. Small measures such as cleaning the camera lens and bringing spare SD cards also increase confidence on site.

Tip 3: Use ground control points for high-accuracy surveys

To use orthophotos as maps, positional accuracy is important. Even if you stitch together aerial photos to create an ortho image, it may be inadequate for surveying if positions are offset. This is where ground control points (GCPs) are useful.

• Place GCPs appropriately: Place a sufficient number of GCPs around and within the area you want to survey. Use clearly distinguishable markers (target markers, etc.) on the ground so they can be easily identified later in photos. Generally, placing several at the area’s corners and near the center is effective.

• Acquire precise coordinates: Measure the coordinates of installed GCPs in advance using a high-precision GNSS survey instrument. If known points or reference points are nearby, you may tie into them. The absolute coordinates of these GCPs are the key to aligning photos to real-world coordinate systems.

• Input into software: When generating ortho images from photos, enter the GCP coordinates into the software or service you use. The processing algorithm matches the GCPs as seen in the photos with the user-supplied real-world coordinates, correcting the entire ortho image to the correct position and scale.

• Use RTK-enabled drones: Recently, drones equipped with RTK positioning have become common. RTK-capable drones can record high-precision self-positioning during flight and may reduce or eliminate the number of GCPs needed. However, RTK does not make errors zero, so for important surveys it is prudent to place a few GCPs for verification of accuracy.

Using GCPs dramatically improves ortho image positional accuracy. For example, without GCPs position errors can be on the order of several meters (several m, i.e., a few to tens of feet), whereas proper use of GCPs can reduce errors to a few centimeters (cm level accuracy (half-inch accuracy)). When overlaying with survey maps or design drawings on site, accurate ortho images without offset prevent later situations where “positions don’t match and the data is unusable.”

Tip 4: Pay attention to weather, lighting conditions, and safety measures

Drone photogrammetry is greatly affected by weather and the surrounding environment, so pay close attention to site conditions. Forcing a flight under poor conditions can degrade photo quality or cause accidents, leading to survey failure.

• Check wind speed and precipitation: Wind during flight affects both safety and image quality. Generally, strong winds of 5 m/s or more can destabilize the drone and cause image blur or missed shots, and are hazardous. Even light rain can ruin images if droplets land on the lens, so avoid flying in rain or fog. Check the weather forecast and choose a day with stable conditions.

• Consider lighting conditions: Sunlight conditions are important in photogrammetry. In early morning or late afternoon when the sun is low, long shadows are cast on the ground and dark shadows can appear in ortho images. If possible, shoot when the sun is higher to minimize shadow impact. Slight overcast can be ideal because it produces soft, even light; in clear skies adjust white balance and exposure to avoid severe blown highlights or crushed blacks.

• Check surrounding safety: Pay attention to the surroundings where you will fly. At sites with power lines, tall buildings, cranes, or other obstacles, plan routes and set altitude limits in advance. Restrict access to the flight area and take safety measures to keep unauthorized people away. Always maintain visual line of sight for the drone and deploy spotters as needed.

• Check radio environment: In urban or mountainous areas be mindful of radio interference and GPS reception. In canyons of tall buildings or dense forests satellite signals can be blocked and accurate positioning may be impossible. Unstable communication can cause real-time video to cut out or control to become unreliable, so operate from locations with good signal or prepare backup communication means.

Be mindful of these environmental factors and choose an appropriate time to fly to safely and reliably obtain data. When weather or lighting conditions are poor, be prepared to postpone. Prioritizing safety ultimately leads to higher-quality ortho images.

Tip 5: Verify captured data on site

After the flight, always verify the captured data before leaving the site. Checking images on site for problems reduces the risk of having to revisit for re-shooting due to mistakes discovered later.

• Check images for blur and soft focus: If you have a tablet or laptop, offload data from the drone and zoom images to check for soft focus or blur. The aircraft’s live view is often too small and issues can be missed, so inspecting on a larger screen after shooting is key.

• Check exposure and color consistency: Quickly browse the captured photos to see whether any images are extremely dark or bright. If some images are over- or under-exposed, decide whether to re-shoot that area or change settings and shoot again.

• Verify coverage: Confirm that the area was covered according to the flight plan by checking image location metadata and the number of photos taken. Apps that plot photo capture points on a map or the drone’s flight log make it easier to detect gaps. If any area is missing, immediately perform additional flights to capture it.

• Confirm GCP visibility: If you set GCPs, check that they are clearly visible in the photos. If a marker is too small or indistinct, accurate alignment may be impossible later; consider a low-altitude re-shoot of the vicinity to reinforce coverage.

Ideally, if you find problems on site you can immediately perform additional flights or re-shoots. Although it may feel like extra work, fixing errors on site is far more efficient than discovering missing data later and returning. Even if you can’t check every photo, at minimum verify key shots and counts so you can leave the site with confidence that nothing critical was missed.

Simple surveying with LRTK

We have introduced five points to reliably succeed at ortho generation in drone photogrammetry. Following these tips should greatly reduce failures in the field. In recent years, cloud-based services have also made drone surveying simpler and less error-prone. A representative example is simple surveying using LRTK.

LRTK combines high-precision GNSS technology with cloud photo-processing services to simplify photogrammetry that previously required specialized knowledge and powerful PCs. For example, with simple surveying using LRTK, you upload photos taken by a drone to the cloud and automatically generate point-cloud data with absolute coordinates. Ortho images and cross-sections can also be obtained in a one-stop workflow, eliminating the need to perform complex processing steps individually. This ease of use means non-experts and those without expensive workstations can still obtain high-accuracy survey results, which is a major advantage.

By leveraging such advanced cloud services you can get analysis results soon after data capture and proceed more efficiently. Drone photogrammetry is evolving daily, and adopting tools like LRTK makes it possible for anyone to undertake high-accuracy ortho generation and 3D surveying without fear of failure. If you want reliable field results while improving operational efficiency, consider trying simple surveying with LRTK.

Frequently Asked Questions

What is an ortho image?

An ortho image is an overhead map-like image created by stitching aerial photos together and correcting ground distortions to produce a rectified orthographic projection. Simply put, it is an image corrected so that photos taken by drones or aircraft appear as if viewed directly from above like a map. Distances and areas can be measured accurately on an ortho image, making it useful for surveying and map creation.

Why is image overlap important in drone photogrammetry?

Image overlap (overlap rate) indicates that adjacent photos share sufficient common areas. Higher overlap makes it easier to detect corresponding points between images, improving accuracy of image stitching and 3D reconstruction. If overlap is insufficient, software may fail to compute relative positions between photos correctly, causing offsets, holes in the ortho image, or even processing failure. Therefore, when planning flight routes, ensure sufficient overlap in both forward/back and side directions (generally 80% or more).

Are ground control points (GCPs) necessary for ortho generation?

GCPs are reference points used to align ortho generation results to real-world coordinate systems. They are not strictly mandatory, but are strongly recommended when high survey accuracy is required. Without GCPs and relying only on the drone’s GPS, absolute positional accuracy tends to be coarse—often on the order of meters. Proper use of GCPs can improve accuracy to the centimeter scale. RTK-capable drones can reduce the need for GCPs, but it’s still reassuring to measure a few known points for verification.

What software and PC are needed to create ortho images?

Traditionally, generating ortho images and point clouds required installing photogrammetry (SfM) software on a high-performance PC. Processing many photos typically demanded a workstation with ample memory and a powerful GPU. Recently, cloud-based services that analyze photo data and deliver results have emerged. With such services, users can run ortho generation from a web browser regardless of local PC performance, without preparing specialized software. For example, LRTK’s cloud service automatically generates point clouds and ortho images simply by uploading photos, so you don’t need expensive hardware or advanced software skills.

Can beginners create ortho images with drones?

Yes—beginners can create ortho images with drones if they follow key points. As covered in this article, pre-flight planning, equipment preparation, and proper shooting procedures will allow you to obtain basic ortho images. Additionally, cloud services and user-friendly apps now enable automatic processing of uploaded photos. Start with a small area to practice and gradually learn the techniques; over time you can use drone photogrammetry by yourself without relying on specialists.