Solid Waste Stockpile Monitoring with Drone Photogrammetry on a Budget

Solid Waste Stockpile Monitoring with Drone Photogrammetry on a Budget

Background

Solid waste stockpile monitoring involves the systematic, real-time, or periodic evaluation of waste piles to manage volume, ensure environmental safety, and maintain regulatory compliance. Modern monitoring techniques, such as 3D LiDAR scanners and UAV (drone) photogrammetry, have largely replaced manual, less accurate estimations, allowing for safe, continuous, and high-resolution tracking of waste quantities. 

The following is a step-by-step example to show how local government with limited resources and equipment can monitor and manage their solid waste sites using low cost consumer drones like the DJI mini 4 Pro and single phase GPS/GNSS hand held receivers for ground control with Open Source applications like WebODM. Naturally better results can be achieved with higher grade equipment but I will show in this web blog that anyone can start even with limited resources. 

The Basic Tools and Equipment Needed

The following are the basic tools and equipment needed:
  • Drone: DJI mini 4 Pro (supports waypoint missions) using DJI Fly app.
  • Mission Planning: Litchi hub (website)
  • GPS/GNSS receivers for Ground Control Points (GCP) for airphoto registration. Example Garmin 64s or your mobile phone. If you are using your mobile phone for GCP collection the SW Map app is recommended.
  • WebODM: Open Source program for the creation of orthophotos and point cloud (elevations)
  • QGIS: Powerful Open Source Geographic Information System for the creation of triangulated irregular point network (TIN) for contouring and volumetric calculation.
  • CAD: For more accurate calculations AutoDesk Civil CAD or GWN-DTM (digital terrain modelling) software if available.
In this web blog we will try to just use open source tools for the project. In all cases you will need a basic understanding of the equipment and applications you are using. It is recommended that you review some of the other blogs for addition background information. Alternatively there are many YouTube videos which you can review as you proceed.

Note: the items highlighted in blue are the tools and apps used in this exercise.

The Proces that will be Applied

We will be using the following flowchart for this exercise:


  1. Drone Mission: The drone mission (air photo flight waypoints) for the SW stockpile site was planned using hub.flylitchi.com. Note you must select the drone model used. In this case it is the DJI mini 4 Pro. Because DJI does not provide the SDK access to the flight controller for the low cost drones, the work around is to use the Litchi hub to create a KMZ file of the mission that needs to be uploaded to the drone for the DJI Fly app to transfer the waypoint data for the flight mission. Note that this is a special KMZ file that is not compatible to Google Earth use. 
    An example of how to load the KMZ file: How to Load Custom Waypoint KMZ file
  2. GCPs (Ground Control Points):  For more accuracy you should use targets or mark locations with washable spray paint (corners of structures, etc.) before you fly your mission. Special black and white targets work best. These should be distributed around the project area. More information on GCPs: Ground Control Points
  3. Air Photos: The air photos are downloaded from the micro SD card on the drone to a folder on your personal computer (PC) for processing with WebODM. If you have GCPs they will need to be prepared with WebODM in a specific GCP file that is uploaded together with the air photos. Follow the WebODM tutorial for the instructions on how this is done. Picking GCPs in WebODM
  4. WebODM: Once the air photos are uploaded to WebODM with or without GCPs you can process the images to create the orthophoto and point cloud file which you can download on to your PC. WebODM is a powerful Open Source application which runs as a container inside Docker on your PC. The installation is complex but it is possible if you follow the instructions carefully. WebODM Installation
  5. QGIS: QGIS originally called Quantum GIS is a powerful Open Source Geographic Information System (GIS) that local governments can use for their operations, management and decision support. It can be the basis of the municipalities data management and can be used for infrastructure, maintenance, planning and cadastre. This is the tool we will use for estimating and monitoring of the stockpile. Here is a website for learning about the capabilities and power of QGIS: Spatial Learning Paths
  6. TIN Model & Contours: Use QGIS to import the point cloud CSV (comma separated values) file and create a TIN model which you can contour. 
  7. Orthophoto: Import the raster orthophoto image and compare it to the contours. You will see that the vegetation will create anomalies if they are near the stockpile. These anomalies can be selected and deleted (weeded) so that you will get a more realistic ground elevation around the vegetation growth areas. This is similar to the way Lidar eliminates vegetation to give you the estimated ground elevation. The Lidar applications do this mathematically, we will do it visually by identifying vegetation in the orthophoto image and deleting those anomalous points.
  8. Regenerate Cleaned TIN Model: Rebuild the TIN with the anomalous vegetation peaks weeded to create a clean TIN surface for volume calculation. Normally you would do this with the site before you fill and then again after you fill to get the volume difference. In this case we do not have a before drone mission so we will attempt to estimate the before condition based on remote sensing of the site using historical satellite imagery. 

The Solid Waste Stockpile Monitoring Project

Remote Sensing

The Copan Ruinas Solid Waste Management Assessment Update 2026 remote sensing timelines showed that the solid waste site could be seen being prepared for stockpiling in March 2015. The ground was being levelled adjacent to the first two lagoons of the sewage treatment plant. The estimate is that the ground is level from the top of the lagoons to the vegetated river bank.



In January 2018 the imagery shows the SW site fully operational with expansion the northwest lagoons before the Copan river flood and breaching of the south lagoon.


You can see that the landfill is encroaching on the access perimiter of the sewage lagoons and some solid waste is deposited ont he berm between the first and second lagoons. The following image in December 2022 shows the breached bank and loss of about 30 to 40 percent of the solid waste into the Copan river due to the flood.


Imagery in 2025 showed that the main stockpile was capped with soil and today the northwest piles have also been capped with a layer of soil. This is where we are calculating the volume of the SW stockpile. A substancial amount has been lost due to flooding and that we cannot account for.

Drone Orthophoto of the site February 2026

The image below is the uncontrolled orthophoto of the SW site completed with the DJI drone and WebODM. 


Using the point cloud data from WebODM the contours of the site is computed. Note the contours of the vegetation (trees). These have to be weeded otherwise they will provide erroneous volumes to the calculation.


The following shows some of the vegetation anomalies that were removed for the main stockpile. The profile tool in QGIS shows the trees and vegetation that would impact volumetrics if they are not removed.


By eliminating the vegetation anomalies a more realistic representation of the surface of the SW stockpile can be achieved for volumetrics. This can be done by comparing the orthophoto image with the contours inside QGIS. Using QGIS you can select and delete the vegetation points in order to create a clean surface of the stockpile.

The weeded vegetation point cloud was used to generate a new TIN model and the recontoured results show the ground without vegetation below.


Based on the profile above and the results from the remote sensing we can reasonably estimate that the ground level at the start of the SW stockpile was 568.3 m (relative to the proper geodetic elevation). Without an original ground survey or point cloud let us use this as the basis for computing the existing main stockpile volume. Using QGIS Volume Calculation Tool plugin the volume of the main stockpile is estimated to be 3828 cubic meters. 


Conclusion

It is feasible to use inexpensive recreational drones like the DJI mini 4 Pro as a serious tool for engineering projects and environmental management and monitoring. This offsets the need to use surveying tools like total stations or even levels and transits to obtain point elevations for a project site. 

At a minimum the built in GPS/GNSS receiver on the DJI drone is sufficient to provide relative point cloud data for engineering projects like road works or site levelling and drainage, or monitoring excavation and fill quantities. If additional precision is needed then the inclusion of GCPs would help. Using RTK GNSS receivers will increase the accuracies even more.

QGIS is a powerful Open Source tool that all municipalities can benefit from. All departments including public works, environmental, cadastral, planning, etc. could share and use GIS data within the organization to better serve their community.

References

  1. GPS Surveying & Drone Mapping for Public Works and Cadastral Department.
    https://gwntech-hon-22729.blogspot.com/2026/02/gps-surveying-drone-mapping-for-public.html
  2. Learning Courses for QGIS. 
    https://spatialthoughts.com/learning-paths/
  3. Copan Ruinas - Solid Waste Management Assessment Update 2026.
    https://gwntech-hon-22729.blogspot.com/2026/02/gps-surveying-drone-mapping-for-public.html
  4. Working with WebODM - Virginia Tech. University Library.
    https://pressbooks.lib.vt.edu/webodm/chapter/working-with-webodm/#:~:text=To%20work%20with%20WebODM%2C%20you,be%20necessary%20for%20many%20applications.

Key QGIS Functions and Plugins Used

  1. Layer > Add Layer > Add Delimited Text Layer - to import comma separated  XYZ points from point cloud csv files.
  2. Processing Toolbox > TIN Interpolation - to create geo tif raster file. Note the points should have UTM coordinates not degrees.
  3. Profile Tool from Plugins, Manage and install Plugins.
  4. Volume Calculation Tool from Plugins, Manage and install Plugins.

Augusto Ribeiro
2026.03.09











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