Woodland creation? There’s an app for that

IT is unlikely to have escaped your notice that there is great interest and a definite focus on woodland creation at the moment, with strong government support for planting, especially in Scotland. Trees are being touted as the answer to climate concerns, stabilising ground, capturing carbon and are the next big thing in construction materials.

This means there is a greater demand for boots on the ground evaluating potential woodland-creation sites and preparing them for planting. Before the trees can be planted, the site needs to be assessed for features and sensitivities, and desk-based research will only get you so far. The site needs to be walked and mapped, and plans marked out, sometimes over remote and difficult terrain. Fencing and ground-preparation specialists need a good guide to the site’s constraints, then once their work is finished, it needs to be checked.

All of this is time-consuming, especially if the areas in question are large. This is where technology can be very useful. Here we’ll focus on the pros and cons of just a couple of options to assist with woodland creation.

A typical orthomosaic map produced by Fountain Forestry.

DRONES – YOUR EYE IN THE SKY

While online satellite maps such as Google Maps and Bing are freely available, they are rarely as up to date as we might like and it can be difficult to tell exactly how old the images are. However, on-demand high-resolution aerial photography is now within the reach of foresters thanks to the growing popularity and reducing cost of unmanned aerial vehicles (UAVs), or drones as they are more commonly called. Some forestry companies have their own pilots with drone licences (PfCO, required by the Civil Aviation Authority for commercial flying), although there are now many specialist companies offering aerial imaging services.

The most commonly used drones, such as the DJI Mavic and Phantom 4 (approx £1,500), fly at up to 120 metres high (the legal limit) for around 20–30 minutes per battery (most drone pilots own many batteries), covering areas of approximately 30 ha in that time. Pre-programmed flight plans are prepared beforehand using a computer or app and take account of the expected wind direction, obstacles, battery capacity and other variables.

Once in the air, the drone’s 20-megapixel camera records images every 4–5 seconds as it travels at around 10 m/s, with images purposely overlapping each other to help with the next step: using visible features and GPS locations to stitch the images together into a photomosaic, a single high-resolution image covering the area of interest. This is usually a top-down view, but other angles and video of the area can also be produced.

These aerial photographs are georeferenced for use with geographic information systems (GIS) and can be useful in initial site inspection: features that can be missed on the ground are sometimes obvious from the air, especially when looking for archaeology. Landscape features that change over time, such as watercourses and existing vegetation, can be accurately mapped, and plans made for buffer zones and mulching. The images can also help improve the accuracy of forestry grant scheme claims, with planting areas precisely mapped, minimising risks to landowners. Generating these images is much quicker and less hazardous than mapping on foot with GPS.

Once the initial site preparation has been completed, another flight can assist with additional time-saving steps: the image can be used to calculate the precise area that has been prepared for planting, the exact length of fence installed, lengths and positions of drains and other features, to compare with and update the original plans. This means that contractors’ work – and invoices – can be more accurately assessed.

Aerial images can also generate terrain models, and 3D ‘point clouds’ which provide a land cover surface, used for 3D visualisation, helpful for planning in sensitive or difficult sites.

Plus, while not yet common, work is ongoing into automated feature detection using aerial images. Popular targets are individual tree detection, monitoring tree health, and volume estimations based on species and height. Cameras recording different sections of the light spectrum (e.g. near-infrared) can be attached, providing additional insights into ground moisture and vegetation.

However, something that anyone can do with an aerial photo and GIS is create virtual sample plots: pick a plot centre on your image, add a 5.6-metre buffer zone around it, and with sharp eyes you can usually count numbers of mounds, or trees planted. In this way you can calculate stock density or numbers of trees required for beat-up.

AVENZA GPS MAP APP: YOU ARE HERE

Another invaluable tool for managers and contractors is a smartphone app called Avenza Maps (www.avenzamaps.com) that provides your location in relation to a preloaded map. It’s a simple idea, using your phone’s in-built GPS location function, but takes the pain out of working out whether you are putting the species boundaries, fence, or buffer zone in the right place. With most people owning a smartphone, it is a convenient way of connecting yourself with your mapped plans without having to take extra equipment on site.

It’s easy to use: you prepare your map with all the relevant details and plans in GIS, save it as a georeferenced PDF, then upload it to your phone and the app. On site no internet is required as long as the map has already been uploaded, just a GPS signal which shouldn’t be a problem in the usually open spaces of woodland-creation sites. Then you are presented with a dot showing where you are on your map. Simple! Georeferenced maps can be shared with other workers who can then easily locate the boundaries you have set.

The app also has the functionality to add placemarks with comments and photos, so you can note areas which have been missed during planting, for example. These can then be downloaded and fed back into your GIS system. If required, you can also take measurements and use geofencing – implementing a virtual boundary which triggers a warning if crossed.

Avenza Maps is available free of charge for recreational use (which allows three maps to be uploaded at any one time), and with a subscription for commercial use (for which there is no limit to your map uploads, which can be PDF or shapefiles direct from your GIS system).

The only problem we’ve found when testing this app is the location accuracy, which is only as good as the GPS ability of your phone. This is at best an accuracy of 3–5 metres in areas with plentiful mobile tower coverage, but can drop in remote locations with worse coverage, and can also be affected by weather and the surrounding environment. So with this caveat in mind, Avenza Maps is a useful tool, but there may be situations where a GPS unit is better suited to the task.

FUTURE SCANNING

Technology for mensuration of standing stock seems to be the next big thing, but there are also exciting new options to help with woodland-creation planning and execution. This article has only discussed two innovations, but these are the most common and simple to access. More technology is likely to be developed, including functions built into GIS systems for automatic drone image analysis, and also more options for 3D visualisations built from aerial photos and the terrain data that can be calculated from the imagery. And there is plenty more to come. Looking to the future, the next obvious step would be to create interactive augmented reality 3D views of woodland-creation plans – hold up your smartphone and take a walk around the site to see how it will look in 20, 30 or 50 years.

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