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I have GPS nav in my phone, and I also have a garmon. Neither will penetrate the summer canopy of a hard maple stands, or Northern White cedar in the U.P...
"Conclusions GPS usage in a tropical forest!In this study, submeter accuracy was achieved under forest canopy by using Earthmate USBGPS, but it was not done constantly. For one reason, consumer GPS receivers such asEarthmate USB GPS are influenced by multipath effects more easily than high-end GPSreceivers that sometimes use multipath rejection technology. In fact, there were multipatherrors seen in the data collected at A5, and positional errors for code-phase DGPS wereunstable especially under forest canopy due to possible effects of multipath. On the otherhand, carrier-phase DGPS with GPS PostPro 2.0 eliminated such negative effects, and (submeter accuracy was achieved at all three points after 300 minutes of elapsed time ofmeasurements.) As for the distance between the remote and base stations, (it is recommendedthat GPS measurements should be conducted for longer time such as 120 or 300 minutes only)http://www.ecologyandsociety.org/vol5/iss2/art6/To measure the positions of trees, we placed the GPS antenna against individual boles in both undisturbed forest and near canopy gaps. If neither GPS nor differential (DGPS) readings were obtained at ground level, ( trees were ascended using a safety belt and Buckingham tree climbers (essentially, steel gaffs and shanks strapped to the feet).) Data on the attributes and spatial location of individual trees were then downloaded onto a portable laptop computer and exported into GIS software (ArcView version 3.1, Environmental Systems Research Institute, Redlands, California, USA). ________________________________________RESULTSIn conditions under which the sky was relatively open and free of obstruction, a minimum of four satellites in optimum position and signals of optimum strength were always located and tracked, allowing consistent collection of high-accuracy data in real time. (Often, however, ground-based attempts to log differentially corrected data points beneath the forest canopy resulted in total failure.) Although the GPS receiver was, at times, able to locate the required minimum of four satellites, the narrow signal parameters needed for high-quality, differentially corrected positions were rarely obtained. ( Attempts to plot trees in the forest interior failed because the SNR became so convoluted by heavy foliage that even the minimum requirement of tracking four satellites was rarely achieved) (Fig. 2A). In trials with the GPS antenna positioned near canopy gaps, the hand-held data logger indicated favorable SNR levels, but these were confounded by conditions of poor satellite positioning or high PDOP (Fig. 2B). (In an attempt to mitigate these factors, we climbed trees in order to escape as much signal interference as possible. From a height of 25–30 m, the SNR increased and PDOP decreased sufficiently to allow high-accuracy DGPS measurement. This strategy always worked, although the GPS receiver sometimes required 10–15 min to locate satellites with the optimum PDOP required for collecting the highest quality) measurements. In 135 DGPS measurements, we tracked 6.65 ± 0.92 satellites (mean ± 1 SD), and PDOP was 2.48 ± 0.7FIELD DATA AND ALLOMETRIC EQUATIONS.—We did not attempt tocompare locations of individual trees between field and image data. (In a previous study at La Selva, Costa Rica, Read et al. (2003) foundthat it was extremely difficult to acquire submeter locations using aGlobal Positioning System (GPS) receiver even for large emergenttrees. Location of individual canopies is complicated because of
Is there anyway to do some aerial photos and plot gps tree locations from the photos?
Let the monkey do it.
Wow! Each tree has to have a set of coordinates before it can be cut!
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