In Land Cover Mapping, Technology, UAS

In an increasingly populated, financially-strained, and ecologically-stressed world, scientists are facing mounting pressure to find quick answers to social and environmental challenges. But, In the field of ecology, solutions almost never come quickly.  They take miles of hiking through uninviting terrain, months of laboratory sample testing, and weeks of data analyses to devise some of the most basic answers to the most basic questions.  Fortunately for ecologists, new uses of technology, particularly airborne remote-sensing technology, are helping them obtain these answers more quickly than they were able to only a few years ago.

Satellite imagery has been used for at least 45 years, since NASA’s Landsat satellite was launched. Landsat imagery has been extremely valuable for ecologists – it provides a rich record of temporal change over large landscapes. With it, users can show the persistent march of deforestation or the spreading tendrils of urban growth.  However, until recently most imagery from satellites lacked fine-scale resolution, so had limited utility in fields like ecology where fine details about species diversity or spatial patterns in an ecosystem are needed.

But, this is changing as new-generation satellites have specialized sensors which can capture the details of plant growth, biomass, ground-level moisture and climate and weather patterns. Imagery from these new satellites, in addition to aircraft with sensors and photographic equipment are providing an increasing wealth of information about land cover, land use and biodiversity patterns.

360 degree view of Santa Cruz area compiled by the SIG team using UAS imagery (c).

Now the newest airborne tools in the ecologists’ toolbox are Unmanned Aircraft Systems (UAS) – more commonly known as drones.  Drones have received a bad rap in recent years due to their use in warfare, espionage, and other less-than-positive applications.  Nevertheless, their use is growing in the ecology because of their ease of use, adaptability, high resolution, and cost effectiveness. And in an era of federal cuts in science funding for the environmental sciences, making studies cost-effective is key. Drones are now are becoming so popular that a new organization,, is dedicated to helping people devise ways to use them for good.

Most, but not all UAS are fully autonomous vehicles that fly along pre-planned flight paths. They systematically take photographs of the landscape, capture video footage, record data with LIDAR/RADAR, or track animals with radio telemetry devices.  They capture all of this data at extremely fine resolutions (less than 5 cm), allowing scientists to easily and remotely detect a wealth of information that previously might have only been available through ponderous trekking through possibly dangerous terrain.

SIG is among this growing cadre of conservationists using drones to collect data and complete work more quickly, safely and creatively than they could in the past.  One example of SIGs recent work with UAVs was the recently completed Tahoe Key Property Owner Association (TKPOA) Impervious Land Cover Mapping and Quantification project.

The DJI Mavic, hard at work over the Lake Tahoe area. Photo by Erin Alvey (c)

Pavement, buildings, and other sorts of “impervious land cover” seal off soil surfaces, which prevents natural groundwater recharge and rainwater to run off. This leads to decreases in water quality, poor wildlife and fish habitat, heat islands, and lower air quality. The Tahoe Regional Planning Agency (TRPA) regulates the amount of impervious surface allowed on a parcel of land and requires property owners to prepare assessments to quantify impervious surfaces to ensure they are complying with these regulations. This helps TRPA to identify actions that can mitigate negative environmental effects.

SIG was contracted to collect high-resolution imagery for 16 different parcels at South Lake Tahoe. Image collection was performed using a DJI Mavic Pro quadcopter UAS. A quadcopter is a very maneuverable type of UAS, and allowed the team to work in confined areas, with exact lift-offs and landings.  It collected at least 20 photos per parcel. The 3 cm/pixel resolution photos were stitched together using cloud-based photo processing to create a 2D image of the parcel.

Once images were combined into a mosaic for each parcel, ArcGIS 10.5 software was used to ensure they were spatially accurate. The software matched three or more points in each image to a base map with known geographic coordinates (in this case it was the ESRI base map, one of several widely-used base maps).

The eBee, another type of UAS, getting prepped for use by a SIG UAS Team Member. Photo by Erin Alvey (c).

Features in the images were then classified based on 15 different types of landcover. Pavement and building footprints and how they related to TRPA-designated land use types and lake set-back requirements were of most interest to the team, given the project objectives. The SIG UAS Team also used a digital elevation model from high-resolution LiDAR data to develop contour lines and to define Lake Tahoe’s high-water elevation.

This project was the first time that a UAS was used to map and quantify impervious cover for the TRPA. Typically, more costly but traditional land-based surveys are deployed for this application. That’s important because as this technology becomes more readily available, meeting regulatory requirements like this will become quicker and cheaper for property owners, as well as local governments (and therefore local tax-payers) who need to monitor regulations.

And its’ not just these groups  that will benefit.  UAS can be used by NGOs who need to survey land for land planning, philanthropies that want to conserve certain types of forest, or private ranchers who simply need to check on their herds.  Like all technology, drones can be used for good as easily as they can for harm. The good news is that UAS technologies are getting placed into the hands of people trying to make our planet a cleaner, more livable place.



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