Using Unmanned Aerial Vehicles (UAV) vs walking – a comparison Background A project in Benin contacted GKIM to try to use UAV’s to map cashew nut farmer, and track agricultural practice indicators. Hypothesis: UAV’s could collect farmer boundaries faster, more accurately, and possibly automate some agricultural practice indicators with software analysis. Although the project had hiccups, it was a learning experience for GKIM and the vendor in terms of: - standardizing logistics processes - finding the best software for imagery processing - identifying what indicators could be collected automatically - mapping boundaries Determinate's of Success The below two points were key to the success of the UAV project. - Data collection would be faster using UAV’s compared to walking the plots to mark the boundaries - Farmers marking the boundaries of their farms by drawing on top of the maps would be as accurate as walking the farms The effort of walking the farm boundaries on foot and taking imagery with UAV’s happened simultaneously, so we’re able to make the comparison in terms of time and effort. The learning experience provided a basis for forming UAV capabilities within CRS, which is crucial to helping future programs that want to use UAV’s. Walking the line When the farm boundaries were walked on foot to identify the boundaries, it was done using ESRI’s ArcGIS Collector software, on smart phones. Walked boundaries were considered the accuracy assessment of drawn boundaries. The data collector and the farmer walked the farm boundaries with the smart phone in hand. Walking farmer plots takes a substantial amount of time. A single plot took 30 minutes to walk and it took even more time to find a farmer who knew the boundary and for them to get to the farm. Walking all boundaries of a project, depending on the will require a lot of CRS staff and a lot of mobile devices for data collection. For example, if the project targets 32,000 farmers, and we calculate a minimum of 30 minutes per farmer, it would take 2000 work days to map all of the farms. If we have 100 data collectors and 100 devices, it would take 20 days to map out all the plots. Considering the cost of GKIM recommended mobile device is in the $300 price range, the cost of that data collection would be $30,000 for the equipment alone. Some farms may be impossible to walk, as the terrain may be difficult / impossible to walk. If farms are close together and farmers are easy to coordinate, UAV’s present a substantial ability to save time mapping farmer boundaries. Flight areas must be known prior to arriving to the field to make this time saving a reality. Marking the boundaries using UAV’s A quadcopter can cover about 50 hectares of land in a 20 minute flight. Multiple batteries will allow for multiple flights, covering more area. A fixed wing aircraft can fly for an hour or more, allowing them to cover 200 hectares or more. Pix4D software is suggested to assist in seeing the area flown and avoiding patches that were not flown. Software that is dependent on an internet connection to retrieve this information from the UAV has proven to be problematic due to the high bandwidth needed. Once the UAV captures the imagery, we need to travel back to the office to process it and make it in to a map that we can use. Getting one a single image from that is time consuming, and we recommend this be done over night. After image processing, the image must be printed, a meeting time set to meet with the corresponding farmers. The data collector works with them to identify the farm boundaries using landmarks they are familiar with as farmers may have never seen their property using an aerial view. Once the farmers mark their boundaries on the maps, they are taken back to the office and digitized with ESRI software. GKIM GIS support can assist with this process if time permits. Comparing both approaches Below is an image that compares the walked lines to the boundaries that the farmers drew on top of the UAV scanned images. An analysis was performed to determine the standard deviation of drawing vs walking. The resulting analysis states that the standard deviation for drawing outwards on all of the farms is 0.05 hectares difference, while the standard deviation for drawing inwards is 0.1 hectares per plot. This error could be further reduced with practice and repetition. You can find a link to the analysis here: http://bit.ly/2xxvR1i/ The pilot project mapped 12 plots in total. The yellow lines were the walked lines, while the blue lines represent the hand drawn plot lines. Advantages of using UAV’s over walking the farm boundaries - They can take a fraction of the time to collect the imagery needed compared to walking. This becomes even more cost effective if there’s more farms bundled together - Working with the farmers to draw on top of the imagery can be used to get farmers more familiar with their land, get a closer working relationship with them - Can be used in areas of high risk, where it would be risky to send a human to collect the data - UAV imagery can give you survey grade elevation maps, allowing you to work with farmers to better plan the slope of their plots, planning for landslides, irrigation, land erosion and other factors linked to land slope. - UAV multispectral imagery can give you access to things that the human eye cannot see, such as: - Over / under fertilization for cereal crops and rape seed oil - Some diseases and weeds can be detected - General plant stress - Leveling issues that can effect productivity and water management - Return of investment of using UAV’s in Agriculture can be up to 146% - Repeated flights over the same area can provide changes over time - Better informed and timely decisions about farming practices The use of UAV’s in agriculture needs to be paired with actionable information for UAVs to be relevant to the small farmer. When detecting plant stress, follow up with soil test kits, and disease check is essential for this information to maintain relevance. Cost of UAV’s Below are cost options for аCP to own a UAV: Quadcopter: - UAV cost: $850 up to $25,000 (depends on need) - Software: $310 monthly license OR $4,990 unlimited license. - Onsite training: $6,000 plus airfare and accommodation - Multispectral sensors (optional): $1,300 to $7,000 depending on need - Laptop to process imagery: up to $3,000 Fixed wing: - UAV cost: $20,000 up to $25,000 - Software: $310 monthly license OR $4,990 unlimited license. - Onsite training: $6,000 plus airfare and accommodation - Multispectral sensors (optional): $3,000 to $7,000 depending on need ($25,000 UAV will include multispectral sensors) - Laptop to process imagery: up to $3,000 When to use / not use UAV’s: A couple of factors dictate whether to use UAV’s in a project or not. - Laws and regulations in country Each country has different laws and regulations around the use of UAV’s. It’s very important to determine the rules and regulations before making any investment in UAV’s as some countries have complete bans on using UAV’s. Some would require a license to be obtained, and some are completely lenient to using UAV’s - Distance between farms The bigger the distance between farms that needs to be traveled, and the smaller the farms means more travel between flights by car. This may not result in a positive return of investment and may incur more costs than benefits. - Total size of farm groups If you’re working with farm groups, and they are close together, then it makes financial sense to use UAV’s - High income taxes Some countries have extremely high taxes on UAV’s and other technology products, making them very cost prohibitive. - Indicators that can’t be tracked using UAV’s Even with tools such as multispectral sensors, UAV’s may not be able to tell you everything you need to know, such as what is happening underneath the canopy of a tree. In such cases, manual on foot inspections will work best. How do I know when to use UAV’s and all costs associated? GKIM has been gaining expertise on UAV’s in several sectors. In cases when the expertise does not exist, GKIM can connect your project with an external company that has the expertise to provide this capability. We recommend talking to GKIM to better understand the project needs, restrictions, etc, so that an appropriate technology recommendation can be made specific to your project. Email helpdesk@crs.org with the subject ICT4D help to get started.
