GPS World, February 2019

MAPPING All figures Lidar USA dilemmas Finding a good place for a GPS base station in a cloud forest is no small task Normally we would put the base station on a known reference point so we can easily join the data with other projects In this case we didnt have any such concern We simply needed an area with a clear view of the sky usually this means no obstructions 12 degrees above the horizon However in a forest and in the mountains you take what you can get In our case we found a rock outcropping and placed the unit on it with no tripod It didnt give us the best solution but it worked Ideally we leave the base running for hours to get a good solution Since we had multiple sites to scan this wasnt a problem All sites were within walking distance of the base so there was no concern about being too far away and 30 GPS WORLD WWW GPSWORLD COM FEBRUARY 2019 FIGURES 1 2 AND 3 Left broad overflight area of the cloud forest Top bare earth classified surface of small site Bottom closer site inspection notice non natural occurring mounds adding more problems to the project In PPK mode we can easily be 10 or 20 kilometers from the base with no concern Other Forest Challenges In field processing far from internet or electrical supply requires very judicious battery and especially laptop usage The lack of many things we take for granted can quickly be a show stopper if necessary maybe even a phone call Even back at the hotel where power was available dont count on it While the film crew and archeologists are eager to see results everybody has to wait No power Supposedly this is common and only lasts an hour Three hours pass and everybody goes to bed but the lidar crew Finding the ground should be easy but a new version of software has been installed Theres a kink in our plans Finally after some internet help a call back home the right settings are found and the software begins peeling away the vegetation to reveal the ground The top of each hill several were scanned looked like a primitive fortress with 20 to 30 cylindrical structures clearly spread over the top of each site On one site we identified a tower at least 3 meters in height While areas like this could be scanned with a conventional aerial system collecting much larger areas the UAV lidar solution offers several distinct advantages One of these is just a quick recon of the area Physically being on the ground at the site makes the team much more aware of what is going on Secondly is the far far greater density of points and the ability to collect much more off nadir allowing for more of the vertical structure to be captured FIGURE 4 Areas of interest to archeologist lots of them